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Chemical composition of late-type supergiants. IV. Homogeneous abundances and galactic metallicity trends
In a recent series of papers by Luck and by Luck and Bond on the chemical composition of G and K lb supergiants, (Fe/H) ratios were determined from high-dispersion spectroscopic data for 54 stars. The main results were: (1) that supergiants in the solar neighborhood have about twice the iron content of the Sun (<(Fe/H)> = +0.3); and (2) that supergiants between 7.7 and 10.2 kpc from the galactic center show a steep radial metallicity gradient, d(Fe/H)/dR = -0.24 kpc/sup -1/.
Luck, R.E.
Chemical compositions of four high-latitude A-F supergiants
The atmospheric parameters and chemical composition of HR 6144, HD 161796, 89 Her, and HR 7671, four representative members of the class of A- and F-type supergiants lying at high Galactic latitudes, are determined. The abundance results for HR 6144, HD 161796, and 89 Her are strongly atypical of Population I supergiants in that they are slightly metal-poor and have an overabundance of both C and N. Their locations in the H-R diagram and the difficulty of assigning them to Population I suggest that high-latitude supergiants are low-mass stars in a post-AGB evolutionary stage. However, they do not reveal the heavy s-process element enhancements seen in highly evolved B stars. HR 7671 differs from the other three stars in that it is very metal-poor, slightly deficient in C and O, has s-process abundances enhanced by a factor of four above solar, and has a surprising amount of Li. It may be a post-AGB star descended from a Li-rich S-type star. 81 refs.
Luck, R.E.; Bond, H.E.; Lambert, D.L. (Case Western Reserve Univ., Cleveland, OH (USA) Space Telescope Science Institute, Baltimore, MD (USA) Texas Univ., Austin (USA))
Chemical compositions of 26 distant late-type supergiants and the metallicity gradient in the galactic disk
From an analysis of high-dispersion Mount Wilson spectroscopic data, we have obtained atmospheric parameters and chemical abundances for 26 distant supergiants of spectral types G through M. Iron-to-hydrogen ratios wth respect to the Sun, (Fe/H), can be determined from this material with an uncertaintly of +- 0.2 dex.
Luck, R.E.; Bond, H.E.
Myocardial Protective Effect of Warm Blood, Tepid Blood, and Cold Crystalloid Cardioplegia in Coronary Artery Bypass Grafting Surgery
To compare the myocardial effects of cardioplegia by warm blood, tepid blood, and cold crystalloid during coronary artery bypass grafting (CABG). Methods Patients undergoing CABG surgery at Kaunas University Hospital between 2000 and 2004 were ran- domized into three groups (n=156), receiving a different method of cardioplegia. Intermittent antegrade warm blood cardioplegia was used in 51 patients, tepid blood cardioplegia
Edmundas Sirvinskas; Linas Nasvytis; Laima Raliene; Jolanta Vaskelyte; Adolfas Toleikis; Sonata Trumbeckaite
Chemical abundances and winds of massive stars in M31: a B-type supergiant and a WC star in OB 10
NASA Astrophysics Data System (ADS)
We present high quality spectroscopic data for two massive stars in the OB 10 association of M31, OB 10-64 (B0 Ia) and OB 10-WR1 (WC6). Medium resolution spectra of both stars were obtained using the ISIS spectrograph on the William Herschel Telescope. This is supplemented with Hubble Space Telescope STIS UV spectroscopy and Keck I HIRES data for OB 10-64. A non-local thermodynamic equilibrium (LTE) model atmosphere and abundance analysis for OB 10-64 is presented, indicating that this star has similar photospheric CNO, Mg and Si abundances to solar neighbourhood massive stars. A wind analysis of this early B-type supergiant reveals a mass-loss rate of M?=1.6�10-6Msolaryr-1, and v?=1650kms-1. The corresponding wind momentum is in good agreement with the wind momentum-luminosity relationship found for Galactic early-B supergiants. Observations of OB 10-WR1 are analysed using a non-LTE, line-blanketed code, to reveal approximate stellar parameters of logL/Lsolar~5.7, T*~75kK, v?~3000kms-1, M?/(Msolaryr-1)~10-4.3 adopting a clumped wind with a filling factor of 10 per cent. Quantitative comparisons are made with the Galactic WC6 star HD 92809 (WR23) revealing that OB 10-WR1 is 0.4 dex more luminous, though it has a much lower C/He ratio (~0.1 versus 0.3 for HD 92809). Our study represents the first detailed, chemical model atmosphere analysis for either a B-type supergiant or a Wolf-Rayet (WR) star in Andromeda, and shows the potential of how such studies can provide new information on the chemical evolution of galaxies and the evolution of massive stars in the local Universe.
Smartt, S. J.; Crowther, P. A.; Dufton, P. L.; Lennon, D. J.; Kudritzki, R. P.; Herrero, A.; McCarthy, J. K.; Bresolin, F.
Effects of immersion in tepid bath water on recovery from fatigue after submaximal exercise in man
This study was conducted to determine whether bathing in tepid water is effective in facilitating recovery from fatigue after submaximal exercise. Subjects were six young healthy male university students. Following cycle exercise at 80% aerobic power ([Vdot]Omax) for l0 min, recovery was observed during and after 10-min bathing. Three conditions were set; (1) water temperature of 38�C, (2) water temperature
Detection of a weak surface magnetic field on Sirius A: are all tepid stars magnetic?
NASA Astrophysics Data System (ADS)
Aims: We aim at a highly sensitive search for weak magnetic fields in main sequence stars of intermediate mass, by scanning classes of stars with no previously reported magnetic members. After detecting a weak magnetic field on the normal, rapidly rotating A-type star Vega, we concentrate here on the bright star Sirius A, taken as a prototypical, chemically peculiar, moderately rotating Am star. Methods: We employed the NARVAL and ESPaDOnS high-resolution spectropolarimeters to collect 442 circularly polarized spectra, complemented by 60 linearly polarized spectra. Using a list of about 1100 photospheric spectral lines, we computed a cross correlation line profile from every spectrum, leading to a signal-to-noise ratio of up to 30 000 in the polarized profile. Results: We report the repeated detection of circularly polarized, highly asymmetric signatures in the line profiles, interpreted as Zeeman signatures of a large-scale photospheric magnetic field, with a line-of-sight component equal to 0.2 � 0.1 G. Conclusions: This is the first polarimetric detection of a surface magnetic field on an Am star. Using rough estimates of the physical properties of the upper layers of Sirius A, we suggest that a dynamo operating in the shallow convective envelope cannot account for the field strength reported here. Together with the magnetic field of Vega, this result confirms that a new class of magnetic objects exists among non Ap/Bp intermediate-mass stars, and it may indicate that a significant fraction of tepid stars are magnetic. Based on observations obtained at the Bernard Lyot Telescope (TBL, Pic du Midi, France) of the Midi-Pyr�n�es Observatory, which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.
Petit, P.; Ligni�res, F.; Auri�re, M.; Wade, G. A.; Alina, D.; Ballot, J.; B�hm, T.; Jouve, L.; Oza, A.; Paletou, F.; Th�ado, S.
Spectroscopy of F supergiants with infrared excess
Atmospheric parameters, abundances of 26 chemical elements and radial velocities, all based on CCD echelle spectra, are presented for two peculiar F supergiants with a large infrared excess: IRAS 07134+1005 and IRAS 18095+2704. A moderate underabundance of metallicity is revealed for both stars, [Fe\\/H]_=-1.0 and -0.78 dex, respectively. The significant overabundance of CNO elements is confirmed for IRAS 07134+0115: [C\\/Fe]=1.08
V. G. Klochkova
Molecular and dust shells around cool supergiants
NASA Astrophysics Data System (ADS)
The last decade has witnessed a remarkable expansion of our knowledge of the chemistry occuring in the huge envelopes surrounding supergiants. The development of highly sophisticated infrared - submillimeter telescopes was crucial for this progress due their potential to detect gas-phase and solid-state species. Instruments such as Herschel, ISO, IRAM, APEX, SMA, etc. were key for these discoveries. The opening of ALMA end 2011 heralded the start of a new era thanks to an increase in sensitivity and spatial resolution of ca. 2 orders-of-magnitude. Although some supergiants have now been studied in quite some detail, a comprehensive understanding of the main chemical routes and the impact of some dominant physical processes is still lacking. In this talk, I give an overview of the current knowledge on the molecular and dust content in shells around supergiants. I discuss the importance of some chemical formation routes and their relation with some dynamical process. I end the talk with some suggestion for future research.
Decin, Leen
Physical parameters and wind properties of galactic early B supergiants
NASA Astrophysics Data System (ADS)
We present optical studies of the physical and wind properties, plus CNO chemical abundances, of 25 O9.5-B3 Galactic supergiants. We employ non-LTE, line blanketed, extended model atmospheres, which provide a modest downward revision in the effective temperature scale of early B supergiants of up to 1-2 kK relative to previous non-blanketed results. The so-called "bistability jump" at B1 (Teff � 21 kK) from Lamers et al. is rather a more gradual trend (with large scatter) from v?/vesc�3.4 for B0-0.5 supergiants above 24 kK to v?/vesc� 2.5 for B0.7-1 supergiants with 20 kK ? Teff ? 24 kK, and v?/vesc� 1.9 for B1.5-3 supergiants below 20 kK. This, in part, explains the break in observed UV spectral characteristics between B0.5 and B0.7 subtypes as discussed by Walborn et al. We compare derived (homogeneous) wind densities with recent results for Magellanic Cloud B supergiants and generally confirm theoretical expectations for stronger winds amongst Galactic supergiants. However, winds are substantially weaker than predictions from current radiatively driven wind theory, especially at mid-B subtypes, a problem which is exacerbated if winds are already clumped in the H? line forming region. In general, CNO elemental abundances reveal strongly processed material at the surface of Galactic B supergiants, with mean N/C and N/O abundances 10 and 5 times higher than the Solar value, respectively, with HD 2905 (BC0.7 Ia) indicating the lowest degree of processing in our sample, and HD 152236 (B1.5 Ia+) the highest.
Crowther, P. A.; Lennon, D. J.; Walborn, N. R.
Water masers in red supergiants
NASA Astrophysics Data System (ADS)
Results of long-term monitoring of circumstellar water maser sources in red supergiants are reviewed. The observations were carried out in 1980-2006 on the RT-22 radio telescope at Pushchino Radio Astronomy Observatory. We discuss the results for the semiregular variable M-supergiant VX Sgr and non-variable M-supergiant IRC-10414. In addition to our single-dish data, very-long-baseline interferometry results are invoked. VX Sgr and IRC-10414 display a characteristic water line profile, which suggests the presence of a rotating circumstellar disc and a bipolar outflow.
Pashchenko, M. I.; Rudnitskij, G. M.; Samodurov, V. A.; Tolmachev, A. M.
Properties of Galactic B Supergiants
NASA Astrophysics Data System (ADS)
Physical and wind properties of Galactic B supergiants are presented based upon non-LTE line blanketed model atmospheres, including Sher 25 toward the NGC 3603 cluster. We compare H? derived wind densities with recent results for SMC B supergiants and generally confirm theoretical expectations for stronger winds amongst Galactic supergiants. Mid B supergiant winds are substantially weaker than predictions from current radiatively driven wind theory, a problem which is exacerbated if winds are already clumped in the H? line forming region. We find that the so-called `bistability jump' at B1 (Teff � 21kK) from Lamers et al. is rather a more gradual downward trend. CNO elemental abundances, including Sher 25, reveal partially processed material at their surfaces. In general, these are in good agreement with evolutionary predictions for blue supergiants evolving redward accounting for rotational mixing. A few cases, including HD 152236 (?1 Sco), exhibit strongly processed material which is more typical of Luminous Blue Variables. Our derived photospheric [N/O] ratio for Sher 25 agrees with that for its ring nebula, although a higher degree of CNO processing would be expected if the nebula originated during a red supergiant phase, as is suspected for the ring nebula ejected by the B supergiant progenitor of SN 1987A, Sk--69� 202. Sher 25 has an inferred age of �5 Myr in contrast with �2 Myr for HD 97950, the ionizing cluster of NGC 3603, so it may be a foreground object or close binary evolution may be responsible for its unusual location in the H-R diagram.
Crowther, P. A.; Lennon, D. J.; Walborn, N. R.; Smartt, S. J.
Betelgeuse and the Red Supergiants
NASA Astrophysics Data System (ADS)
Betelgeuse is one of the most magnificent stars in the sky, and one of the nearest red supergiants. Astronomers gathered in Paris in the Autumn of 2012 to decide what we know about its structure, behaviour, and past and future evolution, and how to place this in the general context of the class of red supergiants. Here I reflect on the discussions and propose a synthesis of the presented evidence. I believe that, in those four days, we have achieved to solve a few riddles.
van Loon, J. Th.
Supergiants and the Galactic metallicity gradient. II. Spectroscopic abundances for 64 distant F- to M-type supergiants
The metallicity gradient in the Galactic disk from in situ stars with visual magnitude ranging from 6 to 10 is analyzed. Atmospheric parameters and detailed chemical abundances for 64 Population I supergiants of spectral types F through M and luminosity classes Ia through II have been determined. The derived Fe/H ratios ranging from -0.5 to + 0.7 show a mean value of +0.13 with an estimated uncertainty of + or - 0.2. A subset of 25 supergiants fainter than 7th magnitude lying in the direction of the Galactic center shows a Fe/H mean of +0.18 + or - 0.04, while a similar sample of 15 faint supergiants lying in the direction of the Galactic anticenter shows a lower Fe/H mean of +0.07 + or - 0.06. For a sample of bright supergiants analyzed by Luck and Lambert (1985), the mean abundance pattern for all 64 stars showed the following: deficient C and O along with enhancement of N, indicating mixing of CNO-cycled material to the stellar surfaces; an apparent Sr enhancement attributed to departures from LTE; and an essentially solar pattern of other chemical elements. 50 refs.
Luck, R.E.; Bond, H.E. (Case Western Reserve Univ., Cleveland, OH (USA) Space Telescope Science Institute, Baltimore, MD (USA))
NASA Technical Reports Server (NTRS)
This quarterly report is comprised of a paper, "Rotational Modulation of B Supergiant Winds" presented at the ESO workshop "Cyclical Variability in Stellar Winds." Presented is a 30-day IUE time series of the BO Ia HD 91969, a member of the Carina open cluster NGC 3293, which showed, among other things, that wind lines that probe more deeply into the wind vary more regularly.
Massa, D.; Fullerton, A. W.; Prinja, R. K.
On the Balmer discontinuity of BIa supergiants
NASA Astrophysics Data System (ADS)
Observed Balmer discontinuities of BIa supergiants, obtained in the Barbier-Chalonge-Divan system using 13-color photometry, are compared with those predicted using classical models of stellar atmospheres. The differences noted between observations and theory for beta = 1 are shown to be a function of the effective temperature. Radii of the supergiants are usually higher when the spectral type is later, suggesting that models of extended atmospheres may explain both the Balmer discontinuities of the supergiants and their far-UV flux distributions.
Zorec, Juan; Mercado-Ibanez, Roger
NASA Technical Reports Server (NTRS)
We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasizes the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M qi) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can differ by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in turns of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.
Massa, Derck; West, D. (Technical Monitor)
NASA Technical Reports Server (NTRS)
We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasises the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters, but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M (dot) q(sub i)) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can differ by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in terms of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.
Massa, D.; Oliversen, R. (Technical Monitor)
Nonradial pulsations of upsilon Orionis and supergiants
The overshooting nonradial mode driving for a pulsating star very close to the main sequence (..nu.. Ori) and for the non radial pulsations of an A supergiant not too unlike ..cap alpha.. cyg is discussed. (GHT)
Cox, A.N.
Chromospheres and Winds of Cool Supergiants
NASA Astrophysics Data System (ADS)
Massive stars lose material via stellar winds on evolutionary timescales in the supergiant phases of their lives. In particular, stars between about 3 and 40 M_{?} spend a significant fraction of their post-main sequence lifetime as red supergiants of spectral classes G-M. The upper limit to red supergiant masses appears to be constrained by mass loss that increases rapidly with stellar mass. Although mass loss from red supergiants has been observed since the 1930s, we still don't understand the mechanism that drives it. Unfortunately, most observations of mass loss from supergiant stars include the entire, unresolved, circumstellar envelope, and provide no spatial information, especially about the inner part of the wind where mass loss starts. One way to achieve spatially resolved observations is to observe the select group of red supergiants with main-sequence companions (typically B stars) in eclipsing orbits. As the hot, and much smaller (in physical size, not mass) companion moves behind the supergiant during eclipse ingress, the line of sight sweeps through successively deeper layers of the supergiant's extended outer envelope. This circumstellar envelope superimposes an absorption upon the continuum of the hot companion, and this "chromospheric" eclipse spectrum can be used to infer the density, velocity and ionization state along the line of sight. By repeated observation of the spectrum of the binary through eclipse, the structure of the supergiant's outer atmosphere can be derived. All of this was realized decades ago. But, despite this potential, the early promise of the binary method to reveal atmospheric structure in red supergiants has never been fully achieved. There are many reasons for this: the additional data reduction complication caused by the need to separate composite spectra, the uncertain perturbing effect of the companion on the structure of the circumstellar envelope being probed, the difficulty of removing light scattered by the circumstellar envelope into the line of sight (which appears as emission), and sometimes, because of the sheer complexity of the chromospheric absorption line spectrum observed (e.g. VV Cephei). The situation has improved considerably with the advent of ultraviolet observations from space, which mostly obviate the need to disentangle composite spectra. The International Ultraviolet Explorer has provided a huge amount of spectroscopic data of limited resolution and signal-to-noise, while the Hubble Space Telescope GHRS and STIS spectrographs have obtained a limited number of observations of superb spectral resolution and signal-to-noise. The Far Ultraviolet Spectroscopic Explorer has also contributed results shortward of Lyman-alpha. In this talk, I will summarize the present state of the binary method, and present observations, results and prospects for several red supergiant binaries.
Bennett, P. D.
Red supergiants and neutrino emission. II.
NASA Technical Reports Server (NTRS)
Investigation of the variation with stellar mass of the ratio of the numbers of blue and red supergiants. Statistical data for supergiants in young open clusters and subgroups of associations are collected to supplement a more restricted list presented earlier. Improved methods are used to identify hydrogen-burning supergiants, as well as faint supergiant remnants of binary mass exchange, and to arrange the bright evolved supergiants in order of their masses. Neither of these two operations requires knowledge of stellar distances or luminosities. Relevant published work on stellar evolution, rotation, mass loss, and duplicity is used to predict upper and lower limits on the blue-to-red ratio. It is concluded that the observed paucity of very massive red supergiants (and of carbon stars) confirms and extends the trend previously observed, and thereby supports the idea of neutrino-induced acceleration of the carbon burning and later phases of evolution; the h and chi Persei association shows the same dependence of the blue-to-red-ratio on stellar mass as do other clusters and associations; and a moderate decrease of the blue-to-red ratio is observed with increasing galactocentric distance in the Galaxy (as in M33) and seems to be due to a relative scarcity of extremely young stars in distant galactic regions.
Stothers, R.
Spectroscopy of F supergiants with infrared excess
NASA Astrophysics Data System (ADS)
Atmospheric parameters, abundances of 26 chemical elements and radial velocities, all based on CCD echelle spectra, are presented for two peculiar F supergiants with a large infrared excess: IRAS 07134+1005 and IRAS 18095+2704. A moderate underabundance of metallicity is revealed for both stars, [Fe/H]_=-1.0 and -0.78 dex, respectively. The significant overabundance of CNO elements is confirmed for IRAS 07134+0115: [C/Fe]=1.08 dex, [N/Fe]=1.03 dex and [O/Fe]=0.6 dex. For IRAS 18095+2704 these overabundances are less marked: [X/Fe]~=0.5 dex,but they are real. Large excesses of lanthanides are derived for both stars. Significant unexplained non-LTE effects occur, revealed by differences for many metals in the abundances obtained from neutral and ionized atomic lines. All of the characteristics of the IRAS sources studied are consistent with the hypothesis that they are at a post-AGB evolutionary stage.
Klochkova, V. G.
Supergiants and the galactic metallicity gradient. I. 27 late-type supergiants in the inner-arm regions
From an analysis of high-dispersion Kitt Peak echelle data, atmospheric parameters and chemical abundances have been derived for 27 supergiants of spectral type F through M. Since the star studied lie within about 1 kpc of the Sun, their abundances will form the local reference point for extensions of this study to larger distances. The derived (Fe/H) ratios range from -0.6 to +0.1 dex, show a mean value of -0.15 dex, and have an internal uncertainty of +- 0.2 dex.
Luck, R.E.
LMC A-F supergiants (Stock+, 1976)
NASA Astrophysics Data System (ADS)
A survey for A-F type supergiants in the Large Magellanic Cloud has been carried out using UV objective prism plates. 890 objects were detected and their spectral types, luminosity classes, magnitudes, and precise positions determined. The survey is practically complete to mpg=12.5 and extends for certain types of stars to mpg=14. It is found that the spatial distribution of the A-F supergiants is not correlated with the distribution of the gas and OB stars of the cloud. This is evidence in support of the tentative identification by Stock and Wroblewski of early-type galactic supergiants well off the plane. Several other implications of this result are also discussed. (2 data files).
Stock, J.; Osborn, W.; Ibanez, M.
Quantitative spectroscopy of BA-type supergiants
NASA Astrophysics Data System (ADS)
Luminous BA-type supergiants have enormous potential for modern astrophysics. They allow topics ranging from non-LTE physics and the evolution of massive stars to the chemical evolution of galaxies and cosmology to be addressed. A hybrid non-LTE technique for the quantitative spectroscopy of these stars is discussed. Thorough tests and first applications of the spectrum synthesis method are presented for the bright Galactic objects ? Leo (A0 Ib), HD 111613 (A2 Iabe), HD 92207 (A0 Iae) and ? Ori (B8 Iae), based on high-resolution and high-S/N Echelle spectra. Stellar parameters are derived from spectroscopic indicators, consistently from multiple non-LTE ionization equilibria and Stark-broadened hydrogen line profiles, and they are verified by spectrophotometry. The internal accuracy of the method allows the 1?-uncertainties to be reduced to ?1-2% in T_eff and to 0.05-0.10 dex in log g. Elemental abundances are determined for over 20 chemical species, with many of the astrophysically most interesting in non-LTE (H, He, C, N, O, Mg, S, Ti, Fe). The non-LTE computations reduce random errors and remove systematic trends in the analysis. Inappropriate LTE analyses tend to systematically underestimate iron group abundances and overestimate the light and ?-process element abundances by up to factors of two to three on the mean. This is because of the different responses of these species to radiative and collisional processes in the microscopic picture, which is explained by fundamental differences of their detailed atomic structure, and not taken into account in LTE. Contrary to common assumptions, significant non-LTE abundance corrections of ~0.3 dex can be found even for the weakest lines (W?? 10 m�). Non-LTE abundance uncertainties amount to typically 0.05-0.10 dex (random) and ~0.10 dex (systematic 1?-errors). Near-solar abundances are derived for the heavier elements in the sample stars, and patterns indicative of mixing with nuclear-processed matter for the light elements. These imply a blue-loop scenario for ? Leo because of first dredge-up abundance ratios, while the other three objects appear to have evolved directly from the main sequence. In the most ambitious computations several ten-thousand spectral lines are accounted for in the spectrum synthesis, permitting the accurate reproduction of the entire observed spectra from the visual to near-IR. This prerequisite for the quantitative interpretation of intermediate-resolution spectra opens up BA-type supergiants as versatile tools for extragalactic stellar astronomy beyond the Local Group. The technique presented here is also well suited to improve quantitative analyses of less extreme stars of similar spectral types.
Przybilla, N.; Butler, K.; Becker, S. R.; Kudritzki, R. P.
Supergiant Stars as Extragalactic Probes of Cosmic Abundances and Distances
NASA Astrophysics Data System (ADS)
The determination of chemical composition and distances of galaxies is crucial for constraining the theory of galaxy formation and evolution in a dark energy and cold dark matter dominated universe. However, the standard technique using HII regions to determine the metallicity of star forming galaxies, nearby and at high redshift, is subject to large systematic uncertainties that are poorly understood and the determination of accurate distances using Cepheids suffers from uncertainties caused by the metallicity dependence of the period luminosity relationship and extinction and crowding corrections. Multi-object spectroscopy of blue and red supergiant stars - the brightest stars in the universe at visual and NIR wavelengths - provides an attractive alternative. I will present results accumulated over recent years for galaxies in the Local Group and beyond out to a distance of 8 Mpc and will discuss the potential of future work with TMT and E-ELT. Combining the photon collecting power of these next generation telescopes with Adaptive Optics we will be able to study individual supergiant stars in galaxies as distant as the Coma cluster. With spectroscopy of the integrated light of young very massive Star Super Clusters and simple population synthesis techniques we can reach out ten times further
Kudritzki, R.
Mass loss in red giants and supergiants
NASA Technical Reports Server (NTRS)
The circumstellar envelopes surrounding late-type giants and supergiants were studied using high resolution, photoelectric scans of strong optical resonance lines. A method for extracting the circumstellar from the stellar components of the lines allowed a quantitative determination of the physical conditions in the envelopes and the rates of mass loss at various positions in the red giant region of the HR diagram. The observed strengthening of the circumstellar spectrum with increasing luminosity and later spectral type is probably caused by an increase in the mass of the envelopes. The mass loss rate for individual stars is proportional to the visual luminosity; high rates for the supergiants suggest that mass loss is important in their evolution. The bulk of the mass return to the interstellar medium in the red giant region comes from the normal giants, at a rate comparable to that of planetary nebulae.
Sanner, F.
Dusty Blue Supergiants: News from High-Angular Resolution Observations
NASA Astrophysics Data System (ADS)
An overview is presented of the recent advances in understanding the B[e] phenomenon among blue supergiant stars in light of high-angular resolution observations and with an emphasis on the results obtained by means of long baseline optical stellar interferometry. The focus of the review is on the circumstellar material and evolutionary phase of B[e] supergiants, but recent results on dust production in regular blue supergiants are also highlighted.
de Wit, W. J.; Oudmaijer, R. D.; Vink, J. S.
Fossil dust shells around luminous supergiants
NASA Technical Reports Server (NTRS)
The observed frequency with which infrared excesses appear in F, G, and K supergiants of luminosity class Ia supports the idea that these excesses arise in a 'fossil' circumstellar dust shell that was formed during a prior M-super-giant phase of evolution. The required leftward evolution of the star on the H-R diagram would then imply that the Ledoux, rather than the Schwarzschild, criterion for convective mixing is the correct criterion to use in stellar evolution calculations.
Stothers, R.
NASA Astrophysics Data System (ADS)
In the present work the spatial distribution of the red supergiants in M33 galaxy is discussed. The observational data exhibit stellar groups of high stellar density. The smallest 60 groups with stellar density corresponding to signal-to-noise ratio S/N > 5 have a mean size of 8.1" (?30 pc). They are real stellar associations in M33. The size of the largest stellar groups found in M33 is of about 200" (~0.8 kpc) and is typical for a stellar complex.
Vassilev, O.; Vassileva, L.; Ivanov, G.; Vassilev, D.
Modeling of the spectrum of Cygnus OB2 No. 7 supergiant
NASA Astrophysics Data System (ADS)
We report the results of modeling of the spectrum of the O3 If* Cyg OB2 No. 7 supergiant in a broad wavelength range. We determine the physical properties and chemical composition of its atmosphere not assuming the presence of local thermodynamic equilibrium. The atmosphere reveals an excess of nitrogen X(N)/ X(N)? = 3.2 and the carbon and oxygen deficiency X(C)/ X(C)? = 0.08, X(O)/ X(O)? = 0.09. The lines in the stellar spectrum are divided into three groups which fail to be describedwithin a single model. Themodels describing each of these groups differ by themass-loss rate and the law of wind velocity variation. Thus, the numerical modeling suggests that the wind of the supergiant is heterogeneous. In addition, this paper describes the features of the CMFGEN code used and investigates the sensitivity of its results to the variations of different parameters.
Maryeva, O. V.; Klochkova, V. G.; Chentsov, E. L.
Medium-resolution J-band spectroscopy of individual red supergiant stars is a promising tool to investigate the chemical composition of the young stellar population in star-forming galaxies. As a continuation of recent work on iron and titanium, detailed non-LTE (NLTE) calculations are presented to investigate the influence of NLTE on the formation of silicon lines in the J-band spectra of red supergiants. Substantial effects are found resulting in significantly stronger absorption lines of neutral silicon in NLTE. As a consequence, silicon abundances determined in NLTE are significantly smaller than in local thermodynamic equilibrium (LTE) with the NLTE abundance corrections varying smoothly between -0.4 dex and -0.1 dex for effective temperatures between 3400 K and 4400 K. The effects are largest at low metallicity. The physical reasons behind the NLTE effects and the consequences for extragalactic J-band abundance studies are discussed.
Bergemann, Maria; Kudritzki, Rolf-Peter; Wuerl, Matthias [Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str.1, D-85741 Garching (Germany)] [Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str.1, D-85741 Garching (Germany); Plez, Bertrand [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS, F-34095 Montpellier (France)] [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS, F-34095 Montpellier (France); Davies, Ben [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 OHA (United Kingdom)] [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 OHA (United Kingdom); Gazak, Zach, E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: email@example.com, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com, E-mail: email@example.com [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)] [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
Long term variability of B supergiant winds
NASA Technical Reports Server (NTRS)
The object of this observing proposal was to sample wind variability in B supergiants on a daily basis over a period of several days in order to determine the time scale with which density variability occurs in their winds. Three stars were selected for this project: 69 Cyg (B0 Ib), HD 164402 (B0 Ib), and HD 47240 (B1 Ib). Three grey scale representations of the Si IV lambda lambda 1400 doublet in each star are attached. In these figures, time (in days) increases upward, and the wavelength (in terms of velocity relative to the rest wavelength of the violet component of the doublet) is the abscissa. The spectra are normalized by a minimum absorption (maximum flux) template, so that all changes appear as absorptions. As a result of these observations, we can now state with some certainty that typical B supergiants develop significant wind inhomogeneities with recurrence times of a few days, and that some of these events show signs of strong temporal coherence.
Massa, Derck L.
Energy Distributions of B Supergiants in the Large Magellanic Cloud.
National Technical Information Service (NTIS)
It is shown that line-blanketed, LTE, plane-parallel model atmosphere calculations provide excellent fits to the ultraviolet-through-visual energy distributions of B supergiants in the Large Magellanic Cloud. The models were computed using Kurucz's (1979)...
E. L. Fitzpatrick
Direct imaging with a hypertelescope of red supergiant stellar surfaces
NASA Astrophysics Data System (ADS)
High angular resolution images obtained with a hypertelescope can strongly constrain the radiative-hydrodynamics simulations of red supergiant (RSG) stars, in terms of intensity contrast, granulation size and temporal variations of the convective motions that are visible on their surface. The characterization of the convective pattern in RSGs is crucial to solve the mass-loss mechanism which contributes heavily to the chemical enrichment of the Galaxy. We show here how the astrophysical objectives and the array configuration are highly dependent to design a hypertelescope. For a given field of view and a given resolution, there is a trade-off between the array geometry and the number of required telescopes to optimize either the (u,v) coverage (to recover the intensity distribution) or the dynamic range (to recover the intensity contrast). To obtain direct snapshot images of Betelgeuse with a hypertelescope, a regular and uniform layout of telescopes is the best array configuration to recover the intensity contrast and the distribution of both large and small granulation cells, but it requires a huge number of telescopes (several hundreds or thousands). An annular configuration allows a reasonable number of telescopes (lower than one hundred) to recover the spatial structures but it provides a low-contrast image. Concerning the design of a pupil densifier to combine all the beams, the photometric fluctuations are not critical (Delta photometry < 50%) contrary to the residual piston requirements (OPD < ?/8) which requires the development of an efficient cophasing system to fully exploit the imaging capability of a hypertelecope.
Patru, F.; Chiavassa, A.; Mourard, D.; Tarmoul, N.
Infrared giants vs. supergiants. II. CO observations
NASA Astrophysics Data System (ADS)
We report systematic observations of millimeter CO emission from a sample of 109 oxygen-rich evolved stars (AGB and supergiants), colour-selected from the IRAS Point Source Catalog (0.69 < S_{25microns }/S_{12microns } < 1.20). CO(1-0) has been searched with good sensitivity in 81 sources (74% of the sample). CO(1-0) is detected in 54 sources and a significant upper limit has been achieved in 27 sources. In our previous paper we reported on the statistical results of these observations. We showed that in almost 50% of the sources, the ratio of the IRAS 60;microns flux to CO intensity, {cal R} = S60/T_mb(1-0), is larger by a factor of 3 to more than 10 than what is expected according to the correlation found by \\cite[Nyman et al. (1992)]{nym92}. Supergiants only exhibit very high values (raise 0.6exhbox {> 200). In most cases, the observed spread in the values of this ratio can be explained by a large range of luminosities. This leads to a new criterion to identify AGB stars: an object with {cal R} < 150 must have a low mass progenitor. Here we study the correlations between {cal R} and various physical properties of the sources. Most sources with high values of {cal R} also have low galactic latitudes, small IRAS variability indices, and early spectral types (typically M1-M5). Conversely, there is no dependence on the IRAS colours, nor on the intensity of silicate 10;microns emission. However, a few AGB stars exhibit large {cal R}; other factors than luminosity are required to explain these values. Different hypotheses, such as the possible presence of a chromosphere, a low (12) C abundance or a variable mass-loss rate, are examined. Considering the global high OH detection rate ( ~ 67%), we studied the correlations with CO and OH emission. The detection of OH seems to be a useful discriminator of mechanisms that enhance {cal R}.
Josselin, E.; Loup, C.; Omont, A.; Barnbaum, C.; Nyman, L. Aa.; Sevre, F.
Amplitude Variations in Pulsating Red Supergiants
NASA Astrophysics Data System (ADS)
We have used long-term AAVSO visual observations and Fourier and wavelet analysis to identify periods and to study long-term amplitude variations in forty-four red supergiants. Of these, twelve stars had data which were too sparse and/or had low amplitude and/or were without conspicuous peaks in the Fourier spectrum; six stars had only a long (2,500-4,000 days) period without significant amplitude variation. The other twenty-six stars had one or two periods, either "short" (hundreds of days) or "long" (thousands of days), whose amplitudes varied by up to a factor of 8, but more typically 2 to 4. The median timescale of the amplitude variation was 18 periods. We interpret the shorter periods as due to pulsation, and the longer periods as analogous to the "long secondary periods" found in pulsating red giants. We discuss possible explanations for the amplitude variations, including the effects of pulsation, rotation, convection cells, and stochastically-excited pulsations.
Percy, J. R.; Khatu, V. C.
Red supergiants around the obscured open cluster Stephenson 2
NASA Astrophysics Data System (ADS)
Context. Several clusters of red supergiants have been discovered in a small region of the Milky Way close to the base of the Scutum-Crux Arm and the tip of the Long Bar. Population synthesis models indicate that they must be very massive to harbour so many supergiants. Amongst these clusters, Stephenson 2, with a core grouping of 26 red supergiants, is a strong candidate to be the most massive young cluster in the Galaxy. Aims: Stephenson 2 is located close to a region where a strong over-density of red supergiants had been found. We explore the actual cluster size and its possible connection to this over-density. Methods: Taking advantage of Virtual Observatory tools, we have performed a cross-match between the DENIS, USNO-B1 and 2MASS catalogues to identify candidate obscured luminous red stars around Stephenson 2, and in a control nearby region. More than 600 infrared bright stars fulfill our colour criteria, with the vast majority having a counterpart in the I band and >400 being sufficiently bright in I to allow observation with a 4-m class telescope. We observed a subsample of ~250 stars, using the multi-object, wide-field, fibre spectrograph AF2 on the WHT telescope in La Palma, obtaining intermediate-resolution spectroscopy in the 7500-9000 � range. We derived spectral types and luminosity classes for all these objects and measured their radial velocities. Results: Our targets turned out to be G and K supergiants, late (? M4) M giants, and M-type bright giants (luminosity class II) and supergiants. We found ~35 red supergiants with radial velocities similar to Stephenson 2 members, spread over the two areas surveyed. In addition, we found ~40 red supergiants with radial velocities incompatible in principle with a physical association. Conclusions: Our results show that Stephenson 2 is not an isolated cluster, but part of a huge structure likely containing hundreds of red supergiants, with radial velocities compatible with the terminal velocity at this Galactic longitude (and a distance ~6 kpc). In addition, we found evidence of several populations of massive stars at different distances along this line of sight. Based on observations collected at the William Herschel Telescope (La Palma, Spain).Tables 2 and 3 are available in electronic form at http://www.aanda.org
Negueruela, I.; Marco, A.; Gonz�lez-Fern�ndez, C.; Jim�nez-Esteban, F.; Clark, J. S.; Garcia, M.; Solano, E.
Silicate and hydrocarbon emission from Galactic M supergiants
NASA Astrophysics Data System (ADS)
Following our discovery of unidentified infrared (UIR) band emission in a number of M supergiants in h and chi Per, we have obtained 10-?m spectra of a sample of 60 galactic M supergiants. Only three new sources, V1749 Cyg, UW Aql and IRC+40 427, appear to show the UIR bands; the others show the expected silicate emission or a featureless continuum. The occurrence of UIR-band emission in M supergiants is therefore much higher in the h and chi Per cluster than in the Galaxy as a whole. Possible explanations for the origin and distribution of UIR bands in oxygen-rich supergiants are discussed. We use our spectra to derive mass-loss rates ranging from 10^-8 to 10^-4 M_solar yr^-1 for the new sample, based on the power emitted in the silicate feature. The relationship between mass-loss rate and luminosity for M supergiants is discussed, and correlations are explored between their mid-infrared emission properties.
Sylvester, R. J.; Skinner, C. J.; Barlow, M. J.
Hot gas and cool dust around B[e] Supergiants
NASA Astrophysics Data System (ADS)
We propose a joint Chandra/ACIS and Spitzer/IRS survey of plasma and thermal dust emission from CI Cam and five other galactic B[e] supergiant systems that are bright mid-IR sources. The results will test the hypothesis that many such stars harbor quiescent, "CI Cam-like" X-ray sources, and that these sources may be intimately related to the presence of binary companions as well as to the dusty disks recently detected in IRS spectoscopy of B[e] supergiants. ACIS spectrscopy will establish the presence and strength of any Fe fluorescence line emission in these systems. In parallel, the proposed joint Spitzer IRS observations will provide the means to ascertain the origin and evolution of dusty disks around B[e] supergiants.
Kastner, Joel
Hot gas and cool dust around B[e] Supergiants
NASA Astrophysics Data System (ADS)
We propose a joint Chandra/ACIS and Spitzer/IRS survey of plasma and thermal dust emission from CI Cam and five other galactic B[e] supergiant systems that are bright mid-IR sources. The results will test the hypothesis that many such stars harbor quiescent, "CI Cam-like" X-ray sources, and that these sources may be intimately related to the presence of binary companions as well as to the dusty disks recently detected in IRS spectoscopy of B[e] supergiants. ACIS spectrscopy will establish the presence and strength of any Fe fluorescence line emission in these systems. In parallel, the proposed joint Spitzer IRS observations will provide the means to ascertain the origin and evolution of dusty disks around B[e] supergiants.
Kastner, Joel; Buchanan, Catherine; Forrest, Bill; Sahai, Raghvendra; Sargent, Ben
The B Supergiant problem and mass loss through H?
NASA Astrophysics Data System (ADS)
The evolutionary status of B supergiants represents an awkward but important riddle in today's stellar astrophysics. We do not even know the most basic facts of whether B supergiants are burning hydrogen or helium. Until this is resolved, we will not be able to unravel the final evolution of objects such as the progenitor of SN 1987A. What is clear is that we need to understand B supergiant mass loss in order to understand its evolutionary state. Here we present our results from a comprehensive H? analysis with the CMFGEN code over the bistability (BS) region. We have already confirmed the existence of the BS jump at 22,000 Kelvin in H?, and we will discuss the rise and fall of the H? emission over the BS jump in detail.
Petrov, Blagovest; Vink, J. S.; Graefener, G.
Spectral Classification of Cold IRAS Stars: Supergiants
NASA Astrophysics Data System (ADS)
We have observed 72 stars with low resolution optical spectra (85 A/mm with 2.3 A/pixel) covering 6000 to 8800 A in an attempt to identify the spectral type and luminosity class of a number of dusty IRAS sources. These stars were chosen from region IIIa of the van der Veen & Habing color-color diagram, where infrared late-type stars are found with generally strong 10?m silicate emission and often OH maser emission. We present here initial classficiation results. These include the probable identification of 19 new M0--4 supergiants and the re-classification of 3 stars formerly categorized as S stars: IRC+70012 (M8 III), NSV12260 (M8 III) and IRC+60374 (M4 I). \\begin{tabular}{|l|c|c|c|l|} IRAS name & old type & new type & other name 03572+5509 & M4 & M4 I & AG Cam 05361+4644 & M6 & M3 I & IRC+50149 17360-3140 & M6,K5 & M2 I & IRC-30309 17513-2313 & M5 & M4 I & V774 Sgr 18025-2113 & M2 & M3-4 I & IRC-20427 18135-1740 & M3 & M2 I & IRC-20455 18522+0021 & M5 & M4 I & IRC+00392 18539+0026 & M & M4 I & IRC+00396 19229+1708 & M4e & M3-4 I & 19307+1338 & & M0 I & 19325+2346 & K5,M0 & M2-3 I & 20004+2955 & K8 & K2-4 I & V1027 Cyg 20015+3019 & M4 & M4 I & V719 Cyg 22048+5914 & & M4 I & RAFGL 4286 22480+6002 & & M0 I & IRC+60370 22512+6100 & S & M4 I & IRC+60374 23000+5932 & M3 & M3 I & AS Cep 23252+6010 & & M4 I & 23278+6000 & M4 & M4 I & IRC+60409
Winfrey, S.; Barnbaum, C.; Morris, M.; Omont, A.
Late-Type Red Supergiants: Too Cool for the Clouds?
It has long been known that the median spectral types of red supergiants change from M2 I in the Milky Way to M1 I in the Large Magellanic Cloud (LMC) and to K5-7 I in the Small Magellanic Cloud (SMC) (Elias et al 1985, Massey & Olsen 2002). This is now understood in terms of the shifting of the evolutionary
Emily M. Levesque; P. Massey; K. A. Olsen; B. Plez
Dust Around Red Supergiants in the Magellanic Clouds
We have gathered together a unique dataset for red supergiants (RSGs) in the Magellanic Clouds, which can be used to investigate the amount and nature of dust produced by RSGs in different environments. For a sample of 40 RSGs in each of the LMC and the SMC, we have obtained visible spectrophotometry (4000-9000 A), 2MASS photometry (JHK), and photometry in
Stacey N. Bright; J. Chatelain; W. Freeman; G. Clayton; K. Gordon; J. Nordhaus; P. Massey; E. Levesque; B. Plez; K. Olsen; D. Silva
B-type Supergiants in the SMC (Dufton+, 2005)
NASA Astrophysics Data System (ADS)
Table 4 contains the adopted atomic data, equivalent widths and abundance estimates for all the metal lines observed in the SMC supergiants. It also contains data for the SMC near main sequence star AzV 304, which has been used in a differential analysis. (2 data files).
Dufton, P. L.; Ryans, R. S. I.; Trundle, C.; Lennon, D. J.; Hubeny, I.; Lanz, T.; Allende Prieto, C.
<3D> NLTE line formation in the atmospheres of red supergiants
NASA Astrophysics Data System (ADS)
Red supergiants with their enormous brightness at J-band are ideal probes of cosmic chemical composition. It is therefore crucial to have realistic models of radiative transfer in their atmospheres, which will permit determination of abundances accurate to 0.15 dex, the precision attainable with future telescope facilities in galaxies as distant as tens of Mpc. Here, we study the effects of non-local thermodynamic equilibrium (NLTE) on the formation of iron, titanium, and silicon lines, which dominate J-band spectra of red supergiants. It is shown that the NLTE radiative transfer models enable accurate derivation of metallicity and effective temperature in the J-band. We also discuss consequences for RSG spectrum synthesis in different spectral windows, including the heavily TiO-blanketed optical region, and atmospheric structure. We then touch upon challenges of NLTE integration with new generation of 3D hydrodynamical RSG models and present the first calculations of NLTE spectra with the mean 3D model of Betelgeuse.
Bergemann, M.; Kudritzki, R. P.; Davies, B.; Plez, B.; Gazak, Z.; Chiavassa, A.
Yellow Hypergiants as Dynamically Unstable Post-Red-supergiant Stars
NASA Technical Reports Server (NTRS)
According to recent theoretical studies, the majority of single stars more massive than 30 solar mass successfully evolve into red supergiants, but then lose most of their hydrogen envelopes and metamorphose into hot blue remnants. While they are cool, they become dynamically unstable as a result of high radiation pressure and partial ionization of the gases in their outer layers. It is shown here that these unstable red-supergiant models repeatedly shrink and re-expand on a thermal time scale when perturbed by heavy bursts of mass loss. Consequently, they fill up the domain of yellow hypergiants on the Hertzsprung-Russell diagram and display very fast rates of evolution there, as observed.
Stothers, Richard B.; Chin, Chao-wen; Hansen, James E. (Technical Monitor)
Red supergiants as tracers of Perseus Arm structure
NASA Astrophysics Data System (ADS)
We have performed a systematic search for red supergiants in the Perseus Arm (from l = 95 degrees up to l = 150 degrees). For this purpose we made a selection of candidates through photometric criteria, using data from UCAC, USNO and 2MASS catalogs. 747 stars were observed in the spectral region around the infrared Ca triplet (8400-8900 �) at R ~ 10000, using the Intermediate Dispersion Spectrograph (IDS) on the Isaac Newton Telescope (INT, Roque de los Muchachos Observatory). From these data we have obtained radial velocities, spectral type and luminosity class, finding 353 supergiants. Using them we have analysed the distribution in the radial velocity-galactic latitude diagram, tracing the young clusters and galactic structure in this region.
Dorda, Ricardo; Negueruela, Ignacio; Gonzalez-Fernandez, Carlos
Red Supergiants as Cosmic Abundance Probes
NASA Astrophysics Data System (ADS)
The chemical abundances of galaxies provide key constraints to models of their formation and evolution. Unfortunately, the standard method of determining abundances, from the strong emission lines of Hii-regions, is well-known to be subject to large systematic errors, particularly at high metallicities. To address this problem we are currently working on a project to measure a galaxy's chemical abundances from spectral analysis of individual RSGs. By focussing on a spectral window in the J-band which contains few molecular lines, we are able to derive accurate chemical abundances from relatively low resolution data. In fact, we show that this technique can operate at distances of 3-4 Mpc using the VLT, and a factor of 10 further if we target massive RSG-dominated star clusters. Furthermore, in the ELT-era, we show that we can perform abundance analysis on individual stars out to 70 Mpc, and redshifts of 0.1 for star clusters.
Davies, B.; Kudritzki, R.-P.; Plez, B.; Bergemann, M.; Gazak, Z.; Evans, C.
GIANO-TNG spectroscopy of red supergiants in the young star cluster RSGC2
NASA Astrophysics Data System (ADS)
Aims: The inner disk of the Galaxy has a number of young star clusters dominated by red supergiants that are heavily obscured by dust extinction and observable only at infrared wavelengths. These clusters are important tracers of the recent star formation and chemical enrichment history in the inner Galaxy. Methods: During the technical commissioning and as a first science verification of the GIANO spectrograph at the Telescopio Nazionale Galileo, we secured high-resolution (R ? 50 000) near-infrared spectra of three red supergiants in the young Scutum cluster RSGC2. Results: Taking advantage of the full YJHK spectral coverage of GIANO in a single exposure, we were able to identify several tens of atomic and molecular lines suitable for chemical abundance determinations. By means of spectral synthesis and line equivalent width measurements, we obtained abundances of Fe and other iron-peak elements such as V, Cr, Ni, of alpha (O, Mg, Si, Ca and Ti) and other light elements (C, N, Na, Al, K, Sc), and of some s-process elements (Y, Sr). We found iron abundances between half and one third solar and solar-scaled [X/Fe] abundance patterns of iron-peak, alpha and most of the light elements, consistent with a thin-disk chemistry. We found a depletion of [C/Fe] and enhancement of [N/Fe], consistent with CN burning, and low 12C/13C abundance ratios (between 9 and 11), requiring extra-mixing processes in the stellar interiors during the post-main-sequence evolution. Finally, we found a slight [Sr/Fe] enhancement and a slight [Y/Fe] depletion (by a factor of ?2), with respect to solar. Table 3 is available in electronic form at http://www.aanda.org
Origlia, L.; Oliva, E.; Maiolino, R.; Mucciarelli, A.; Baffa, C.; Biliotti, V.; Bruno, P.; Falcini, G.; Gavriousev, V.; Ghinassi, F.; Giani, E.; Gonzalez, M.; Leone, F.; Lodi, M.; Massi, F.; Montegriffo, P.; Mochi, I.; Pedani, M.; Rossetti, E.; Scuderi, S.; Sozzi, M.; Tozzi, A.
Yellow and red supergiants are evolved massive stars whose numbers and locations on the Hertzsprung-Russell (H-R) diagram can provide a stringent test for models of massive star evolution. Previous studies have found large discrepancies between the relative number of yellow supergiants (YSGs) observed as a function of mass and those predicted by evolutionary models, while a disagreement between the predicted and observed locations of red supergiants (RSGs) on the H-R diagram was only recently resolved. Here, we extend these studies by examining the YSG and RSG populations of M33. Unfortunately, identifying these stars is difficult as this portion of the color-magnitude diagram is heavily contaminated by foreground dwarfs. We identify the RSGs through a combination of radial velocities and a two-color surface gravity discriminant, and after re-characterizing the rotation curve of M33 with our newly selected RSGs, we identify the YSGs through a combination of radial velocities and the strength of the O I {lambda}7774 triplet. We examine {approx}1300 spectra in total and identify 121 YSGs (a sample that is unbiased in luminosity above log (L/L{sub Sun }) {approx} 4.8) and 189 RSGs. After placing these objects on the H-R diagram, we find that the latest generation of Geneva evolutionary tracks shows excellent agreement with the observed locations of our RSGs and YSGs, the observed relative number of YSGs with mass, and the observed RSG upper mass limit. These models therefore represent a drastic improvement over previous generations.
Drout, Maria R. [Center for Astrophysics, Harvard University, 60 Garden Street, M-S 10, Cambridge, MA 02138 (United States); Massey, Philip [Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ 86001 (United States); Meynet, Georges, E-mail: email@example.com, E-mail: email@example.com, E-mail: email@example.com [Geneva Observatory, Geneva University, CH-1290 Versoix (Switzerland)
Properties of galactic B[e] supergiants. I. CI Camelopardalis
NASA Astrophysics Data System (ADS)
We present a study of the high-resolution (R=60 000) optical spectrum of the B[e] supergiant CI Cam obtained 4 years after its all-wavelength outburst. The profiles of most of the emission lines show a triple-peaked structure, an effect previously not observed. The Na I D-lines clearly have 2 interstellar absorption components, suggesting that the system is most probably located within the Perseus arm at a distance of le 3 kpc. Uncertainties of the distance toward the object, its luminosity, and physical parameters of the circumstellar disk are discussed. Simple observational tests are suggested to clarify these issues.
Miroshnichenko, A. S.; Klochkova, V. G.; Bjorkman, K. S.; Panchuk, V. E.
Ultraviolet analysis of the peculiar supergiant HD 112374 = HR 4912
NASA Technical Reports Server (NTRS)
The ultraviolet energy distribution of the metal-poor supergiant HD 112374 is analyzed based on observations from the International Ultraviolet Explorer (IUE) satellite for the region between 1200 and 2000 A. A discontinuity was found in the UV spectra at 2600 A which confirmed the low-abundance of heavy elements found by Luck et al. (1983). Values for effective temperature and log g in HD112374 were consistent with the star being a very luminous Population II semi-regular variable. The full observational results are presented in a table.
Bohm-Vitense, E.; Proffitt, C.
40 field red supergiants in the SMC (Meliani+, 1995)
NASA Astrophysics Data System (ADS)
Low-resolution spectra (~5A) for 40 red supergiants in the Small Magellanic Cloud were compared with synthetic spectra, and their metallicities were derived. A mean metallicity of [Fe/He]=-0.71 is found for 38 stars cooler than Teff<4500K. Using the stellar parameters derived, the carbon abundances were determined by comparing synthetic spectra at the G-band region to the observed spectra. A mean {epsilon}(C)=7.85 is found, clearly higher than the low values suggested in the literature for the H II regions. (45 data files).
Meliani, M. T.; Barbuy, B.; Richtler, T.
Yellow and Red Supergiants in the Large Magellanic Cloud
NASA Astrophysics Data System (ADS)
Due to their transitionary nature, yellow supergiants (YSGs) provide a critical challenge for evolutionary modeling. Previous studies within M31 and the Small Magellanic Cloud show that the Geneva evolutionary models do a poor job at predicting the lifetimes of these short-lived stars. Here, we extend this study to the Large Magellanic Cloud (LMC) while also investigating the galaxy's red supergiant (RSG) content. This task is complicated by contamination by Galactic foreground stars that color and magnitude criteria alone cannot weed out. Therefore, we use proper-motions and the LMC's large systemic radial velocity (~278 km s-1) to separate out these foreground dwarfs. After observing nearly 2000 stars, we identified 317 probable YSGs, 6 possible YSGs, and 505 probable RSGs. Foreground contamination of our YSG sample was ~80%, while that of the RSG sample was only 3%. By placing the YSGs on the Hertzsprung-Russell diagram and comparing them against the evolutionary tracks, we find that new Geneva evolutionary models do an exemplary job at predicting both the locations and the lifetimes of these transitory objects.
Neugent, Kathryn F.; Massey, Philip; Skiff, Brian; Meynet, Georges
Properties of Galactic early-type O-supergiants. A combined FUV-UV and optical analysis
NASA Astrophysics Data System (ADS)
Aims: We aim to constrain the properties and evolutionary status of early and mid-spectral type supergiants (from O4 to O7.5). These posses the highest mass-loss rates among the O stars, and exhibit conspicuous wind profiles. Methods: Using the non-LTE wind code cmfgen we simultaneously analyzed the FUV-UV and optical spectral range to determine the photospheric properties and wind parameters. We derived effective temperatures, luminosities, surface gravities, surface abundances, mass-loss rates, wind terminal velocities, and clumping filling factors. Results: The supergiants define a very clear evolutionary sequence, in terms of ages and masses, from younger and more massive stars to older stars with lower initial masses. O4 supergiants cluster around the 3 Myr isochrone and are more massive than 60 M?, while the O5 to O7.5 stars have masses in the range 50-40 M? and are 4 � 0.3 Myr old. The surface chemical composition is typical of evolved O supergiants (nitrogen-rich, carbon- and oxygen-poor). While the observed ranges of carbon and nitrogen mass-fractions are compatible with those expected from evolutionary models for the measured stellar masses, the N/C ratios as a function of age are inconsistent with the theoretical predictions for the four earliest (O4 spectral type) stars of the sample. We question the efficiency of rotational mixing as a function of age for these stars and suggest that another mechanism may be needed to explain the observed abundance patterns. Mass-loss rates derived with clumped-models range within a factor of three of the theoretical mass-loss rates. The corresponding volume-filling factors associated with small-scale clumping are 0.05 � 0.02. Clumping is found to start close to the photosphere for all but three stars, two of which are fast rotators. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer (FUSE) and by the NASA-ESA-SERC International Ultraviolet Explorer (IUE), and retrieved from the Multimission Archive at the Space Telescope Science Institute (MAST). Based on observations collected with the ELODIE spectrograph on the 1.93-m telescope (Observatoire de Haute-Provence, France). Based on observations collected with the FEROS instrument on the ESO 2.2 m telescope, program 074.D-0300 and 075.D-0061.Appendix A is available in electronic form at http://www.aanda.org
Bouret, J.-C.; Hillier, D. J.; Lanz, T.; Fullerton, A. W.
NGC 7419 as a template for red supergiant clusters
NASA Astrophysics Data System (ADS)
Context. The open cluster NGC 7419 is known to contain five red supergiants and a very high number of Be stars. However, there are conflicting reports about its age and distance that prevent a useful comparison with other clusters. Aims: We intend to obtain more accurate parameters for NGC 7419, using techniques different from those of previous authors, so that it may be used as a calibrator for more obscured clusters. Methods: We obtained Str�mgren photometry of the open cluster NGC 7419, as well as classification spectroscopy of ~20 stars in the area. We then applied standard analysis and classification techniques. Results: We find a distance of 4 � 0.4 kpc and an age of 14 � 2 Myr for NGC 7419. The main-sequence turn-off is found at spectral type B1, in excellent agreement. We identify 179 B-type members, implying that there are more than 1200 M? in B stars at present. Extrapolating this to lower masses indicates an initial cluster mass of between 7000 and 10 000 M?, depending on the shape of the initial mass function. We find a very high fraction (?40%) of Be stars around the turn-off, but very few Be stars at lower masses. We also report for the first time a strong variability in the emission characteristics of Be stars. We verified that the parameters of the red supergiant members can be used to obtain accurate cluster parameters. Conclusions: NGC 7419 is sufficiently massive to serve as a testbed for theoretical predictions and as a template to compare more obscured clusters. The distribution of stars above the main-sequence turn-off is difficult to accommodate with current evolutionary tracks. Though the presence of five red supergiants is marginally consistent with theoretical expectations, the high number of Be stars and very low number of luminous evolved B stars hint at some unknown physical factor that is not considered in current synthesis models. Partially based on observations collected at the Nordic Optical Telescope and the William Herschel Telescope (La Palma) and at the 1.93-m telescope at Observatoire de Haute Provence (CNRS), France.Tables 1 and 2 are available in electronic form at http://www.aanda.orgTables 3, 4 and 7 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/552/A92
Marco, A.; Negueruela, I.
Magnetic Fields and Convection in the Cool Supergiant Betelgeuse
NASA Astrophysics Data System (ADS)
We present the outcome of a highly-sensitive search for magnetic fields on the cool supergiant Betelgeuse. A time-series of six circularly polarized spectra was obtained using the NARVAL spectropolarimeter at T�lescope Bernard Lyot (Pic du Midi Observatory (F)), between March and April 2010. Zeeman signatures were repeatedly detected in cross-correlation profiles, corresponding to a longitudinal component of about 1 G. The time-series unveils a smooth increase of the longitudinal field from 0.5 to 1.5 G, correlated with radial velocity fluctuations. We observe a strong asymmetry of Stokes V signatures, also varying in correlation with the radial velocity. The Stokes V line profiles are red-shifted by about 9 km s-1 with respect to the Stokes I profiles, suggesting that the observed magnetic elements may be concentrated in the sinking components of the convective flows.
Petit, P.; Auri�re, M.; Konstantinova-Antova, R.; Morgenthaler, A.; Perrin, G.; Roudier, T.; Donati, J.-F.
Nonthermal X-ray emission from winds of OB supergiants
The mechanisms responsible for the hard X-ray emission of OB supergiants (OBSGs) are investigated theoretically, modifying the periodic-shock model of Lucy (1982). The physical processes discussed include (1) the particle acceleration (PA) mechanism and its effect on the structure of individual shocks, (2) the energy cutoff and spectral index of the relativistic electrons and ions, and (3) the efficiency of PA by shocks and its implications for the number densities of relativistic particles. The model is used to predict the spectrum and intensity of the dominant nonthermal X-ray emission source from OBSGs, and the results are shown to be in good agreement with Einstein Observatory Solid-State Spectrometer observations of three OBSGs in Orion (Cassinelli and Swank, 1983). It is inferred that the surface magnetic fields of OBSGs are no greater than a few G, and that the PA rates are significantly lower than generally predicted for collisionless astrophysical shocks. 66 refs.
Chen, W.; White, R.L. (Johns Hopkins Univ., MD (USA) Space Telescope Science Institute, Baltimore, MD (USA))
Supergiant Complexes of Solar Activity and Convection Zone
NASA Astrophysics Data System (ADS)
The global distribution of solar surface activity (active regions) is apparently connected with processes in the convection zone. The large-scale magnetic structures above the tachocline could in a pronounced way be observable in the surface magnetic field. To get the information regarding large-scale magnetic formations in the convection zone, a set of solar synoptic charts (Mount Wilson 1998 - 2004, Fe i, 525.02 nm) have been analyzed. It is shown that the longitudinal dimensions and dynamics of supergiant complexes of solar surface activity carry valuable information about the processes in the convection zone of the Sun. A clear effect of large-scale (global) turbulence is found. This is a `fingerprint' of deep convection, because there are no such large-scale turbulent eddies in the solar photosphere. The preferred scales of longitudinal variations in surface solar activity are revealed. These are: � 24� (gigantic convection cells), 90�, 180� and 360�.
Arkhypov, O. V.; Antonov, O. V.; Khodachenko, M. L.
s-Process Elements in the M Supergiant ? Ori
NASA Astrophysics Data System (ADS)
We present new results on a study of the weak s-process elemental abundances in the M supergiant a Ori (M2Iab). We have conducted the abundance analysis through comparison of synthetic with observed spectra in the two infrared spectral regions 0.7 - 1.1 ?m and 2.1 - 2.3 ?m, where the molecular and atomic line densities are less than in the optical region and where many of the relevant elements have strong lines. Our results show that there has been weak s-process production occurring during the life of the star and among the s-process elements is Sr the most overabundant with 1.4 dex higher abundance than the sun. The abundance of Fe in ? Ori is essentially solar. Other elements for which we have determined abundances are Rb, Y and Zr. We compare our results to nuclear evolutionary stellar model calculations and discuss their relevance.
Lundqvist, M.; Wahlgren, G. M.
Investigating supergiant fast X-ray transients with LOFT
NASA Astrophysics Data System (ADS)
Supergiant Fast X-ray Transients (SFXT) are a class of High-Mass X-ray Binaries whose optical counterparts are O or B supergiant stars, and whose X-ray outbursts are about 4 orders of magnitude brighter than the quiescent state. LOFT, the Large Observatory For X-ray Timing, with its coded mask Wide Field Monitor (WFM) and its 10 m2 class collimated X-ray Large Area Detector (LAD), will be able to dramatically deepen the knowledge of this class of sources. It will provide simultaneous high S/N broad-band and time-resolved spectroscopy in several intensity states, and long term monitoring that will yield new determinations of orbital periods, as well as spin periods. We show the results of an extensive set of simulations performed using previous observational results on these sources obtained with Swift and XMM-Newton. The WFM will detect all SFXT flares within its field of view down to a 15-20 mCrab in 5 ks. Our simulations describe the outbursts at several intensities (F(2-10keV) = 5.9�10-9 to 5.5 � 10-10 erg cm-2 s-1), the intermediate and most common state (10-11 erg cm-2 s-1), and the low state (1.2 � 10-12 to 5 � 10-13 erg cm-2 s-1). We also considered large variations of NH and the presence of emission lines, as observed by Swift and XMM-Newton.
Romano, P.; Bozzo, E.; Esposito, P.; Ferrigno, C.; Mangano, V.
Elemental abundances of the supergiant stars ? Cygnus and ? Leonis
NASA Astrophysics Data System (ADS)
This study aims to analyse the elemental abundances for the late B type supergiant star ? Cyg and the early A-type supergiant ? Leo using ATLAS9 (Kurucz, 1995; Sbordone et al., 2004), assuming local thermodynamic equilibrium (LTE). The spectra used in this study are obtained from Dominion Astrophysical Observatory and have high resolution and signal-to-noise ratios. The effective temperature and the surface gravity of ? Cyg are determined from the ionisation equilibria of Al I/II, Mg I/II, Fe I/II, Fe II/III, and by fitting to the wings of H? and H? profiles as Teff = 10388 K and log g = 1.80. The elemental abundances of ? Leo are determined using Teff = 9600 K and log g = 2.00, as reported by Przybilla et al. (2006). The ionisation equilibria of C I/II, N I/II, Mg I/II, Ca I/II, Cr I/II and Fe I/II/III are also satisfied in the atmosphere of ? Leo. The radial velocities of ? Cyg and ? Leo are -7.25 � 7.57 km s-1 and 10.40 � 13.37 km s-1, respectively. The derived projected rotational velocities vsini from synthetic spectra are 27 and 2 km s-1 for both stars, respectively. The macroturbulent velocities (?) are 24 � 2 km s-1 and 14.5 � 1.5 km s-1. Also, the microturbulent velocities (?) have been determined for both of stars as 3.5 km s-1. The CNO abundance results of ? Cyg and ? Leo show C deficiency, N overabundance and O in excess.
Tanr?verdi, Taner
IRC -10414: a bow-shock-producing red supergiant star
NASA Astrophysics Data System (ADS)
Most runaway OB stars, like the majority of massive stars residing in their parent clusters, go through the red supergiant (RSG) phase during their lifetimes. Nonetheless, although many dozens of massive runaways were found to be associated with bow shocks, only two RSG bow-shock-producing stars, Betelgeuse and ? Cep, are known to date. In this paper, we report the discovery of an arc-like nebula around the late M-type star IRC -10414 using the SuperCOSMOS H-alpha Survey. Our spectroscopic follow-up of IRC -10414 with the Southern African Large Telescope (SALT) showed that it is a M7 supergiant, which supports previous claims on the RSG nature of this star based on observations of its maser emission. This was reinforced by our new radio- and (sub)millimetre-wavelength molecular line observations made with the Atacama Pathfinder Experiment 12-m telescope and the Effelsberg 100-m radio telescope, respectively. The SALT spectrum of the nebula indicates that its emission is the result of shock excitation. This finding along with the arc-like shape of the nebula and an estimate of the space velocity of IRC -10414 (?70 � 20 km s-1) imply the bow shock interpretation for the nebula. Thus, IRC -10414 represents the third case of a bow-shock-producing RSG and the first one with a bow shock visible at optical wavelengths. We discuss the smooth appearance of the bow shocks around IRC -10414 and Betelgeuse and propose that one of the necessary conditions for stability of bow shocks generated by RSGs is the ionization of the stellar wind. Possible ionization sources of the wind of IRC -10414 are proposed and discussed.
Gvaramadze, V. V.; Menten, K. M.; Kniazev, A. Y.; Langer, N.; Mackey, J.; Kraus, A.; Meyer, D. M.-A.; Kami?ski, T.
Variability and mass loss in IA O-B-A supergiants
NASA Technical Reports Server (NTRS)
Recently completed catalogs of MK spectral types and UBV photometry of 1227 OB stars in the southern Milky Way have been analyzed to investigate brightness and color variability among the Ia supergiants. It is found that brightness variability is common among the O9-B1 supergiants with typical amplitudes about 0.1 and time scales longer than a week and shorter than 1000 days. Among the A supergiants fluctuations in U-B color are found on similar time scales and with amplitude about 0.1. For many early Ia supergiants there is a poor correlation between Balmer jump and spectral type, as had been known previously. An attempt to correlate the Balmer jump deficiency with mass loss rate yielded uncertain results.
Schild, R. E.; Garrison, R. F.; Hiltner, W. A.
The energy distributions of B supergiants in the Large Magellanic Cloud
NASA Technical Reports Server (NTRS)
It is shown that line-blanketed, LTE, plane-parallel model atmosphere calculations provide excellent fits to the ultraviolet-through-visual energy distributions of B supergiants in the Large Magellanic Cloud. The models were computed using Kurucz's (1979) ATLAS atmosphere program, but with lower gravities than were contained in Kurucz's published model grid. The ultraviolet continua of low gravity stars are found to be sensitive to changes in temperature and gravity. Measurements of Teff and log g for ten LMC B supergiants from model atmosphere fits to the energy distributions yield estimates of their radii, luminosities, and masses. Model atmosphere fits suggest that the late B supergiants have significantly lower masses than the earlier B types of the same luminosity, contrary to stellar evolution theory which predicts that B supergiants are in a post-core hydrogen burning phase and should evolve very quickly and at essentially constant mass.
Fitzpatrick, Edward L.
UV wind variability in B supergiants and its implications for wind structures
We discuss why B supergiant winds are particularly well suited for wind studies, and present or refer to dynamic spectra which\\u000a suggest the presence of disks, bifurcated winds, shock formation, rotationally modulated winds and the spontaneous generation\\u000a of wind enhancements. They underscore the strength and richness of wind variability in B supergiants and the challenges these\\u000a phenomena present to theoretical
Derck Massa; Raman K. Prinja
THE DUSTY CIRCUMSTELLAR DISKS OF B[e] SUPERGIANTS IN THE MAGELLANIC CLOUDS
To better ascertain the nature of the infrared excesses that are characteristic of B[e] supergiants, we obtained Spitzer IRS spectroscopy and IRAC/MIPS imaging for a sample of nine B[e] supergiant stars in the Magellanic Clouds. We find that all nine stars display mid- to far-IR spectral and spatial characteristics indicative of the presence of circumstellar dust disks. Several of the sample B[e] supergiants display crystalline silicate features in their IRS spectra, consistent with grain processing in long-lived (i.e., orbiting) disks. Although it is possible that these disks are primordial in origin, large shell structures (with size scales of tens of parsec) are associated with five of the nine B[e] supergiants, suggesting that mass loss has provided the circumstellar material now orbiting these stars. Hence-via analogy to the class of post-asymptotic giant branch stars with binary companions and dusty, circumbinary disks-we speculate that B[e] supergiant stars may be post-red supergiants in binary systems with orbiting, circumbinary disks that are derived from post-main-sequence mass loss.
Kastner, Joel H. [Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Buchanan, Catherine [School of Physics, University of Melbourne, Victoria, 3010 (Australia); Sahai, Raghvendra [NASA/JPL, 4800 Oak Grove Drive, Pasadena, CA 1109 (United States); Forrest, William J. [Department of Physics and Astronomy, University of Rochester, Bausch and Lomb Hall, P.O. Box 270171, Rochester, NY 14627-0171 (United States); Sargent, Benjamin A., E-mail: firstname.lastname@example.com, E-mail: email@example.com [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
Time Series Analysis of the A0 Supergiant HR 1040
NASA Astrophysics Data System (ADS)
A time series analysis of spectroscopic and photometric observables of the A0Ia supergiant HR 1040 has been performed. The data, obtained from 1993 through 2007, include 152 spectroscopic observations from the Ritter Observatory and 269 Stromgren photometric observations from the Four College Automated Photoelectric Telescope (FCAPT). A number of spectroscopic and photometric features have been analyzed and compared, including Wlambda, radial velocities and Stromgren photometric indices. Typical of late B- and early A-type supergiants, HR 1040 has a highly variable stellar wind including High Velocity Absorption (HVA) events. The star was found to have an active phase with large variation in the physical characteristics of the wind and with the potential for HVAs. During the active phase, correlation between the H-alpha absorption equivalent width and blue-edge radial velocity was observed. If an HVA was present, the active phase was found to begin before the onset of the HVA and continue after the end of the event by as much as several weeks. This active phase alternated with a more common quiescent phase marked by little variability and equivalent width - radial velocity correlation and no HVAs. The active phase and HVAs were found to exhibit important connections to photospheric activity. Increases in H-alpha absorption and blue-edge radial velocity at the onset of HVAs was preceded by correlated increases in Si II Wlambda and second moment, with the atmospheric changes indicated by the H-alpha line lagging the photospheric changes seen in Si II by an interval of 13 to 23 days. The observed HVAs were found to be preceded by Si II radial velocity oscillations by an interval of 19 to 42 days. The equivalent width and second moment of the photospheric Si II lambdalambda6347, 6371 lines were found to be highly variable and strongly correlated throughout the two active phases when an HVA is observed but not during the quiescent phase or in the one active phase where no HVA was seen. The Si II Wlambda and second moment showed a short-lived increase during the first few weeks of an HVA and then quickly dropped back to quiescent phase levels. Time series cluster analysis of the two HVAs observed on HR 1040, in addition to three HVAs in alpha Orionis, identified four distinct stages in the development of these events. Possible factors contributing to HVA are discussed, including gas ejection and microturbulence at the photosphere, as well as co-rotation interaction regions (CIR) in the wind. HR 1040 exhibits a broad emission feature near Halpha commonly found in late B- and early A-type supergiants. The broad emission in HR 1040 was found to be variable and not correlated to photospheric or wind observables associated with the active phase. Some indication was found that this feature is limited to a wavelength range of 6532 A to 6597 A. While the wavelength range extends roughly the same amount to either side of H-alpha line center, an asymmetry in the flux of the broad emission is observed, with a local maximum in the flux varying between 6555 A to 6564 A. If this asymmetry is real and not an instrumental effect, it argues against a photospheric origin for this broad emission feature as it would require radial velocities up to -300 km/s, well in excess of the terminal wind speed.
Corliss, David J.
Maser Mapping of Dust-Driven Winds from Red Supergiants
NASA Astrophysics Data System (ADS)
High resolution MERLIN maps of water and OH masers in the circumstellar envelopes of red supergiant stars reveal complex velocity gradients. The water masers appear to emanate from dense clouds 15 to 20 AU in diameter which are being accelerated away from the star. OH masers are mostly seen in regions of more gently increasing velocity which are likely to be less dense. Outside the dust formation zone, the stellar wind is driven by radiation pressure on grains. Chapman & Cohen (1986) found that in VX Sgr the wind continues to speed up out to a thousand or more AU from the star, and derived values for the dust absorption efficiency increasing with distance to account for this. Other authors pointed out grain growth at large distances is unlikely and suggested VX Sgr must have changed its mass loss rate in recent centuries. However this paper reports observations of continuing acceleration in all four supergiants which have now been studied. An increase in the absorption efficiency of dust is still the most likely generally applicable explanation. This paper proposes a new mechanism whereby the grain surface properties (but not the mass) change in the outflow on a timescale of many decades. Using the method of Chapman & Cohen (1986), it is found that at about 100 AU from the star, near the inner edge of the water maser shell, the dust absorption efficiency is kappaD ~ 0.2 m^2 kg^-1. kappaD increases with distance from the star, rising to >~ m^2 kg^-1 (similar to the conventional value for astronomical silicates) in thick circumstellar envelopes reaching high terminal velocities. The low values found nearer the star suggest that initially the dust grains are crystalline or have a composition high in metal oxides which renders them more transparent to the stellar IR radiation. Dust formation, and the influence of the stellar magnetic field on the grains, is also implicated in producing the small scale clumpiness and large scale axisymmetries which are seen in circumstellar envelopes.
Richards, A. M. S.; Yates, J. A.
The spin-up of contracting red supergiants
NASA Astrophysics Data System (ADS)
We report on a mechanism which may lead to a spin-up of the surface of a rotating single star leaving the Hayashi line, which is much stronger than the spin-up expected from the mere contraction of the star. By analyzing rigidly rotating, convective stellar envelopes, we qualitatively work out the mechanism through which these envelopes may be spun up or down by mass loss through their lower or upper boundary, respectively. We find that the first case describes the situation in retreating convective envelopes, which tend to retain most of the angular momentum while becoming less massive, thereby increasing the specific angular momentum in the convection zone and thus in the layers close to the stellar surface. We explore the spin-up mechanism quantitatively in a stellar evolution calculation of a rotating 12 Msun star, which is found to be spun up to critical rotation after leaving the red supergiant branch. We discuss implications of this spin-up for the circumstellar matter around several types of stars, i.e., post-AGB stars, {{B[e]}} stars, pre-main sequence stars, and, in particular, the progenitor of Supernova 1987A.
Heger, A.; Langer, N.
Accretion in supergiant High Mass X-ray Binaries
NASA Astrophysics Data System (ADS)
Supergiant High Mass X-ray Binary systems (sgHMXBs) consist of a massive, late type, star and a neutron star. The massive stars exhibit strong, radiatively driven, stellar winds. Wind accretion onto compact object triggers X-ray emission, which alters the stellar wind significantly. Hydrodynamic simulation has been used to study the neutron star - stellar wind interaction it two sgHMXBs: i) A heavily obscured sgHMXB (IGR J17252-3616) discovered by INTEGRAL. To account for observable quantities (i.e., absorbing column density) we have to assume a very slow wind terminal velocity of about 500 km/s and a rather massive neutron star. If confirmed in other obscured systems, this could provide a completely new stellar wind diagnostics. ii) A classical sgHMXB (Vela X-1) has been studied in depth to understand the origin of the off-states observed in this system. Among many models used to account for this observed behavior (clumpy wind, gating mechanism) we propose that self-organized criticality of the accretion stream is the likely reason for the observed behavior. In conclusion, the neutron star, in these two examples, acts very efficiently as a probe to study stellar winds.
Manousakis, A.; Blondin, J.; Walter, R.
Stellar winds in supergiant High Mass X-ray Binaries
NASA Astrophysics Data System (ADS)
Supergiant High Mass X-ray Binary systems (sgHMXBs) consist of a massive, late type, star and a neutron star. The massive stars exhibit strong, radiatively driven, stellar winds. Wind accretion onto compact object triggers X-ray emission, which alters the stellar wind significantly. Hydrodynamic simulation has been used to study the neutron star - stellar wind interaction it two sgHMXBs: i) A heavily obscured sgHMXB (IGR J17252-3616) discovered by INTEGRAL. To account for observable quantities (i.e., absorbing column density) we have to assume a very slow wind terminal velocity of about 500 km/s and a rather massive neutron star. If confirmed in other obscured systems, this could provide a completely new stellar wind diagnostics. ii) A classical sgHMXB (Vela X-1) has been studied in depth to understand the origin of the off-states observed in this system. Among many models used to account for this observed behavior (clumpy wind, gating mechanism) we propose that self-organized criticality of the accretion stream is the likely reason for the observed behavior.
Manousakis, Antonios; Walter, Roland
Yellow and Red Supergiants in the Local Group
NASA Astrophysics Data System (ADS)
Yellow and red supergiants are the "poor cousins" of massive star studies, often overlooked in favor of strong emission-lined Wolf-Rayets or the spectacular, enigmatic Luminous Blue Variables. Recent studies, however, are proving the truth of Kippenhahn & Weigert (1990)'s claim that these evolved stages act as a "sort of magnifying glass, revealing relentlessly the faults of calculations of earlier phases." Identifying complete samples of YSGs and RSGs among the galaxies of the Local Group is difficult, as foreground dwarfs are nearly indistinguishable from bona-fide extragalactic members. We have succeeded in this task only by using a combination of wide-area photometry surveys combined with spectroscopic followup. Since massive star evolution is greatly affected by mass-loss, and mass-loss rates depend upon metallicity, we have conducted such studies over a range of 10 in metallicity, including the SMC, LMC, M33, and M31. These studies not only allow us to test the stellar evolutionary models, but the identification of these stars provides interesting kinematic information on the youngest stellar populations in these galaxies. We will review here what we have learned over the past few years, and what new questions these studies are raising.
Massey, Philip; Neugent, Kathryn; Drout, Maria; Meynet, Georges
Red supergiants in the Small Magellanic Cloud: The effects of metallicity on narrow-band classification indices
Narrow-band classification photometry, on a six color system that measures near infrared bands of TiO and CN, has been obtained for a set of red supergiants in the Small Magellanic Cloud. To investigate the effects of metallicity on the band strength indices, comparisons are made to supergiants in the LMC and the Galaxy. Two new variable stars are reported.
Robert F. Wing; Kyle M. Walker; D. Jack MacConnell; Edgardo Costa
The luminosities of red supergiants from Wing's eight-color narrow-band infrared photometry
NASA Astrophysics Data System (ADS)
Calibration relations have been obtained for the intrinsic color index 0 ( = 5040/Te, Te being the observed color temperature of a star) and absolute magnitudes M(104) (at = 1.04 , in Wing's narrow-band photometric system), MV and MK as functions of TiO and CN photometric indices for K5-M5 supergiant stars. The accuracy of the distance moduli obtained when using these calibrations is about 0m�2. The distance moduli have been calculated for red supergiants which are members of open clusters. The distance scale for red supergiants based upon the M(104) (TiO, CN) absolute magnitude calibration (the distance modulus of 11m�4 being assumed for the Per OB1 stellar association) agrees with the distance scale for young open clusters based upon uvby?-photometry and Crawford's (1978) ZAMS for B-type stars.
Dambis, A. K.
The Importance of Long Time Domain Observations for Understanding Pulsation in Cepheids and M Supergiants
NASA Astrophysics Data System (ADS)
Continuous monitoring of both Cepheids and type C semiregular variables is essential for understanding their pulsation. Cepheids, for example, can undergo regular, periodic, and irregular changes in pulsation period and amplitude that are attributed to stellar evolution, orbital motion about companions, and stochastic processes, respectively. All such information helps to characterize Cepheids in terms of physical attributes. Similar information is also very useful for pulsating M supergiants, which are still poorly understood in terms of their pulsation. Specific examples are provided by BC Cyg and ? Cep, the former a M3 supergiant displaying regular pulsation, the latter a M1 supergiant apparently pulsating in fundamental and overtone modes. Both appear to provide long-period extensions of the Cepheid period-mass and period-age relations.
Turner, David G.
Properties of galactic B[e] supergiants. III. MWC 300
NASA Astrophysics Data System (ADS)
We present the results of optical and near-IR spectroscopic and mid-IR imaging observations of the emission-line star MWC 300. Its properties and evolutionary state are still under debate (a B[e] supergiant or a Herbig Be star). For the first time we detected radial velocity variations of the photospheric lines and found a correlation between them and those of the He I ?5876 �line. Most of the pure emission lines had stable positions for nearly 20 years. New estimates of the object's luminosity (log L/L?=5.1�0.1), distance (D=1.8�0.2 kpc), and systemic velocity (+26�2 km s-1) were derived. We found that both the circumstellar extinction in the disk-like dusty envelope and the interstellar extinction play a significant role in the attenuation of the stellar brightness. Our 2D modeling of the observed spectral energy distribution in the wavelength range from 0.3 ?m to 1.3 mm suggests that the star is viewed through a gaseous-and-dusty flared disk with an opening angle of 30 �, an inclination angle of 10 �, an equatorial optical depth ?V=3.0, and a total mass of 0.08 M?. We argue that MWC 300 is most likely a binary system, because of the similarities of its observed parameters with those of recognized B[e] binaries. Partially based on observations collected at the Canada-France-Hawaii telescope (CFHT), operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique, and Univeristy of Hawaii.
Miroshnichenko, A. S.; Levato, H.; Bjorkman, K. S.; Grosso, M.; Manset, N.; Men'shchikov, A. B.; Rudy, R. J.; Lynch, D. K.; Mazuk, S.; Venturini, C. C.; Puetter, R. C.; Perry, R. B.
On the Explosion Geometry of Red Supergiant Stars
NASA Astrophysics Data System (ADS)
From progenitor studies, type II-Plateau supernovae (SNe II-P) have been decisively and uniquely determined to arise from isolated red supergiant stars, establishing the most homogeneous --- and well understood --- progenitor class of any type of core-collapse supernova. The precise nature of the mechanism responsible for the stellar explosion, however, remains the subject of considerable debate. A fundamental clue to the nature of the explosion mechanism is explosion geometry: In short, are supernovae round? Because young supernova atmospheres are electron-scattering dominated, their net linear polarization provides a direct probe of early-time supernova geometry, with higher degrees of polarization generally indicating greater departures from spherical symmetry. Here we present spectropolarimetry data for the most well-sampled SN II-P to date, SN 2008bk, and compare (and contrast) the results with those obtained for SN 2004dj, the only other SN II-P for which spectropolarimetry data were obtained with similar fine temporal sampling before, during, and after the fall off of the photometric plateau (Leonard et al. 2006). Both objects are polarized, indicating departures from spherical symmetry, although the timing of the onset -- as well as the persistence -- of the polarization differ between the two objects. Curiously, the detailed spectropolarimetric characteristics of the two objects at the epochs of recorded maximum polarization are extremely similar, feature by feature, suggesting a common cause --- or, at least, geometry. We interpret the data in light of non-Local-Thermodynamic Equilibrium, time-dependent radiative-transfer simulations specifically crafted for SN II-P ejecta. DCL acknowledges support from NSF grant AST-1009571, under which part of this research was carried out. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under observing programs 081.D-0128, 082.D-0151, and 085.D-0391 (PI: Dessart).
Leonard, Douglas C.; Dessart, L.; Hillier, D.; Pignata, G.
Bright flares in supergiant fast X-ray transients
NASA Astrophysics Data System (ADS)
At steady low-luminosity states, supergiant fast X-ray transients (SFXTs) can be at the stage of quasi-spherical settling accretion on to slowly rotating magnetized neutron stars from the OB-companion winds. At this stage, a hot quasi-static shell is formed above the magnetosphere, the plasma entry rate into magnetosphere is controlled by (inefficient) radiative plasma cooling, and the accretion rate on to the neutron star is suppressed by a factor of �30 relative to the Bondi-Hoyle-Littleton value. Changes in the local wind velocity and density due to, e.g. clumps, can only slightly increase the mass accretion rate (a factor of �10) bringing the system into the Compton-cooling-dominated regime and led to the production of moderately bright flares (Lx ? 1036 erg s-1). To interpret the brightest flares (Lx > 1036 erg s-1) displayed by the SFXTs within the quasi-spherical settling accretion regimes, we propose that a larger increase in the mass accretion rate can be produced by sporadic capture of magnetized stellar wind plasma. At sufficiently low accretion rates, magnetic reconnection can enhance the magnetospheric plasma entry rate, resulting in copious production of X-ray photons, strong Compton cooling and ultimately in unstable accretion of the entire shell. A bright flare develops on the free-fall time-scale in the shell, and the typical energy released in an SFXT bright flare corresponds to the mass of the shell. This view is consistent with the energy released in SFXT bright flares (�1038-1040 erg), their typical dynamic range (�100) and with the observed dependence of these characteristics on the average unflaring X-ray luminosity of SFXTs. Thus, the flaring behaviour of SFXTs, as opposed to steady HMXBs, may be primarily related to their low X-ray luminosity allowing sporadic magnetic reconnection to occur during magnetized plasma entry into the magnetosphere.
Shakura, N.; Postnov, K.; Sidoli, L.; Paizis, A.
Quantitative Studies of the Optical and UV Spectra of Galactic Early B Supergiants
NASA Technical Reports Server (NTRS)
We undertake an optical and ultraviolet spectroscopic analysis of a sample of 20 Galactic B0-B5 supergiants of luminosity classes Ia, Ib, Iab, and II. Fundamental stellar parameters are obtained from optical diagnostics and a critical comparison of the model predictions to observed UV spectral features is made. Methods. Fundamental parameters (e.g., T(sub eff), log L(sub *), mass-loss rates and CNO abundances) are derived for individual stars using CMFGEN, a nLTE, line-blanketed model atmosphere code. The impact of these newly derived parameters on the Galactic B supergiant Ten scale, mass discrepancy, and wind-momentum luminosity relation is examined. Results. The B supergiant temperature scale derived here shows a reduction of about 1000-3000 K compared to previous results using unblanketed codes. Mass-loss rate estimates are in good agreement with predicted theoretical values, and all of the 20 BO-B5 supergiants analysed show evidence of CNO processing. A mass discrepancy still exists between spectroscopic and evolutionary masses, with the largest discrepancy occuring at log (L/(solar)L approx. 5.4. The observed WLR values calculated for B0-B0.7 supergiants are higher than predicted values, whereas the reverse is true for B1-B5 supergiants. This means that the discrepancy between observed and theoretical values cannot be resolved by adopting clumped (i.e., lower) mass-loss rates as for O stars. The most surprising result is that, although CMFGEN succeeds in reproducing the optical stellar spectrum accurately, it fails to precisely reproduce key UV diagnostics, such as the N v and C IV P Cygni profiles. This problem arises because the models are not ionised enough and fail to reproduce the full extent of the observed absorption trough of the P Cygni profiles. Conclusions. Newly-derived fundamental parameters for early B supergiants are in good agreement with similar work in the field. The most significant discovery, however, is the failure of CMFGEN to predict the correct ionisation fraction for some ions. Such findings add further support to revising the current standard model of massive star winds, as our understanding of these winds is incomplete without a precise knowledge of the ionisation structure and distribution of clumping in the wind. Key words. techniques: spectroscopic - stars: mass-loss - stars: supergiants - stars: abundances - stars: atmospheres - stars: fundamental parameters
Searle, S. C.; Prinja, R. K.; Massa, D.; Ryans, R.
The galatic and LMC extreme line supergiants compared: IUE observations of the Henize-Carlson and Zoo star samples of massive supergiants. [Large Magellanic cloud (LMC)
NASA Technical Reports Server (NTRS)
The Henize-Carlson sample of galactic massive supergiants, and a comparison between the Galactic and LMC samples are discussed. Several of the stars, notably He3-395 and S 127/LMC, have very similar shell characteristics. There appears to be little difference, other than luminosity, between the LMC and Galactic samples. One star, He3-1482, was detected with the Very Large Array at 6 cm. The UV data is combined with IRAS and optical information.
Shore, S. N.; Sanduleak, N.; Brown, D. N.; Sonneborn, G.; Bopp, B. W.; Robinson, C. R.
What does C II lambda 2325 A emission tell us about chromospheres of red supergiants? - A critical test using Zeta Aurigae-type K supergiants
NASA Technical Reports Server (NTRS)
The limitations of the Carpenter et al. (1985) C II intercombination multiplet method of determining the density and geometric extent of red giant chromospheres are presently tested through observation of the C II 2325 A emission of two K-type supergiants whose empirical model chromospheres have been derived by high-resolution IUE observations at eclipse phases. While the observed C II emission fluxes are well reproduced, much of this emission originates in the high-density lower chromosphere.
Schroeder, K.-P.; Reimers, D.; Carpenter, K. G.; Brown, A.
SUPERNOVA 2008bk AND ITS RED SUPERGIANT PROGENITOR
We have obtained limited photometric and spectroscopic data for supernova (SN) 2008bk in NGC 7793, primarily at {approx}> 150 days after explosion. We find that it is a Type II-Plateau (II-P) SN that most closely resembles the low-luminosity SN 1999br in NGC 4900. Given the overall similarity between the observed light curves and colors of SNe 2008bk and 1999br, we infer that the total visual extinction to SN 2008bk (A{sub V} = 0.065 mag) must be almost entirely due to the Galactic foreground, similar to what has been assumed for SN 1999br. We confirm the identification of the putative red supergiant (RSG) progenitor star of the SN in high-quality g'r'i' images we had obtained in 2007 at the Gemini-South 8 m telescope. Little ambiguity exists in this progenitor identification, qualifying it as the best example to date, next to the identification of the star Sk -69 Degree-Sign 202 as the progenitor of SN 1987A. From a combination of photometry of the Gemini images with that of archival, pre-SN, Very Large Telescope JHK{sub s} images, we derive an accurate observed spectral energy distribution (SED) for the progenitor. We find from nebular strong-intensity emission-line indices for several H II regions near the SN that the metallicity in the environment is likely subsolar (Z Almost-Equal-To 0.6 Z{sub Sun }). The observed SED of the star agrees quite well with synthetic SEDs obtained from model RSG atmospheres with effective temperature T{sub eff} = 3600 {+-} 50 K. We find, therefore, that the star had a bolometric luminosity with respect to the Sun of log (L{sub bol}/L{sub Sun} ) = 4.57 {+-} 0.06 and radius R{sub *} = 496 {+-} 34 R{sub Sun} at {approx}6 months prior to explosion. Comparing the progenitor's properties with theoretical massive-star evolutionary models, we conclude that the RSG progenitor had an initial mass in the range of 8-8.5 M{sub Sun }. This mass is consistent with, albeit at the low end of, the inferred range of initial masses for SN II-P progenitors. It is also consistent with the estimated upper limit on the initial mass of the progenitor of SN 1999br, and it agrees with the low initial masses found for the RSG progenitors of other low-luminosity SNe II-P.
Van Dyk, Schuyler D.; Elias-Rosa, Nancy [Spitzer Science Center/Caltech, Mailcode 220-6, Pasadena, CA 91125 (United States); Davidge, Tim J., E-mail: email@example.com, E-mail: email@example.com [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, B.C., V9E 2E7 (Canada); and others
Nature of the peculiar supergiant HD 101584 (Bakker+, 1996)
NASA Astrophysics Data System (ADS)
We present a study of low- and high-resolution ultraviolet, high-resolution optical CAT/CES spectra and ultraviolet, optical and infrared photometry of the peculiar supergiant HD 101584. From the photometry we learn that the ultraviolet and optical energy distribution cannot be fitted in a consistent way and we need a model in which the UV and optical energy distribution are formed by different gas. The Geneva photometry is best fitted to a B9II Kurucz model, Teff=12000+/-1000K and logg=3.0+/-1.0, with an extinction of E(B-V)=0.49+/-0.05. The observed spectral features in the spectrum of HD 101584 are classified in eight different categories based on the velocity, shape of profile and the identification. The high-excitation HeI (?=20.87eV), NII (?=18.40eV), CII (?=14.39eV) and NI (?=10.29eV) optical absorption lines are formed in the photosphere of a late B-star (e.g. B8-9I-II). These absorption lines show radial velocity variations which are attributed to binary motion, with the secondary being a white dwarf or a low-mass main sequence object. The low-excitation P-Cygni lines in the optical and UV are formed in the wind. The number density of absorption lines in the UV is so large that the wind spectrum acts as an iron curtain in front of the B-star. The terminal velocity of the wind of v{infinity}=100+/-30km/s is consistent with the star being a low-mass post-AGB star and the low effective gravity is attributed to the presence of a nearby, unseen, secondary. We estimate a mass-loss rate of M?=~10-8M?/yr. Narrow absorption and emission lines are observed which are formed in a circumsystem disk with a typical radius of 102R*. (2 data files).
Bakker, E. J.; Lamers, H. J. G. L. M.; Waters, L. B. F. M.; Waelkens, C.; Trams, N. R.; van Winckel, H.
Lithium in late-type giants. II. 31 M giants and supergiants
High resolution, high signal-to-noise spectra have provided Li abundances for 31 M giants and supergiants. The spectrum around the Li I 6707 A doublet is depressed by unresolved TiO lines. A spectrum synthesis technique was developed to account for the TiO line blanketing and to extract the Li abundance.
Luck, R.E.; Lambert, D.L.
CNO abundances in the quintuplet cluster M supergiant 5-7
NASA Technical Reports Server (NTRS)
We present and analyze infrared spectra of the supergiant VR 5-7, in the Quintuplet cluster 30 pc from the Galactic center. Within the uncertainties, the [C/H],[N/H], and [O/H] abundances in this star are equal of Ori, a star which exhibits mixing of CNO processed elements, but distinct from the abundance patterns in IRS 7.
Ramirez, S. V.; Sellgren, K.; Blum, R.; Terndrup, D. M.
Dynamical Mass of the O-Type Supergiant in Zeta Orionis A.
National Technical Information Service (NTIS)
Aims. A close companion of Orionis A was found in 2000 with the Navy Precision Optical Interferometer (NPOI), and shown to be a physical companion. Because the primary is a supergiant of type O, for which dynamical mass measurements are very rare, the com...
C. A. Hummel G. Belle M. Nieva O. Stahl T. Rivinius
First Stellar Abundance Measurements in the Galactic Center: The M Supergiant IRS 7.
National Technical Information Service (NTIS)
The first measurement of the photospheric abundances in a star at the Galactic center are presented. A detailed abundance analysis of the Galactic center M2 supergiant IRS 7 was carried out using high-resolution near- infrared echelle spectra. The Fe abun...
J. S. Carr K. Sellgren S. C. Balachandran
The Evolution of Massive Stars. I. Red Supergiants in the Magellanic Clouds
We investigate the red supergiant (RSG) content of the SMC and LMC using multiobject spectroscopy on a sample of red stars previously identified by BVR CCD photometry. We obtained high-accuracy (<1 km s-1) radial velocities for 118 red stars seen toward the SMC and 167 red stars seen toward the LMC, confirming most of these (89% and 95%, respectively) as
Philip Massey; K. A. G. Olsen
Quantitative studies of the optical and UV spectra of Galactic early B supergiants. I. Fundamental parameters
NASA Astrophysics Data System (ADS)
Aims: We undertake an optical and ultraviolet spectroscopic analysis of a sample of 20 Galactic B0-B5 supergiants of luminosity classes Ia, Ib, Iab, and II. Fundamental stellar parameters are obtained from optical diagnostics and a critical comparison of the model predictions to observed UV spectral features is made. Methods: Fundamental parameters (e.g., {T_eff}, {log L*}, mass-loss rates and CNO abundances) are derived for individual stars using CMFGEN, a nLTE, line-blanketed model atmosphere code. The impact of these newly derived parameters on the Galactic B supergiant {T_eff} scale, mass discrepancy, and wind-momentum luminosity relation is examined. Results: The B supergiant temperature scale derived here shows a reduction of about 1000-3000 K compared to previous results using unblanketed codes. Mass-loss rate estimates are in good agreement with predicted theoretical values, and all of the 20 B0-B5 supergiants analysed show evidence of CNO processing. A mass discrepancy still exists between spectroscopic and evolutionary masses, with the largest discrepancy occurring at {log (L/L?}) 5.4. The observed WLR values calculated for B0-B0.7 supergiants are higher than predicted values, whereas the reverse is true for B1-B5 supergiants. This means that the discrepancy between observed and theoretical values cannot be resolved by adopting clumped (i.e., lower) mass-loss rates as for O stars. The most surprising result is that, although CMFGEN succeeds in reproducing the optical stellar spectrum accurately, it fails to precisely reproduce key UV diagnostics, such as the N V and C IV P Cygni profiles. This problem arises because the models are not ionised enough and fail to reproduce the full extent of the observed absorption trough of the P Cygni profiles. Conclusions: Newly-derived fundamental parameters for early B supergiants are in good agreement with similar work in the field. The most significant discovery, however, is the failure of CMFGEN to predict the correct ionisation fraction for some ions. Such findings add further support to revising the current standard model of massive star winds, as our understanding of these winds is incomplete without a precise knowledge of the ionisation structure and distribution of clumping in the wind. Appendix A is only available in electronic form at http://www.aanda.org
Searle, S. C.; Prinja, R. K.; Massa, D.; Ryans, R.
Spectroscopic studies of Cepheids (S Cru, AP Pup, AX Cir, S TrA, T Cru, R Mus, S Mus, U Car) and semiregular bright supergiants (V382 Car, HD 75276, R Pup) in the southern hemisphere
NASA Astrophysics Data System (ADS)
We present the second part of the results of our work to investigate the atmospheric parameters and chemical composition of southern-hemisphere Cepheids obtained by analyzing 24 spectra for eight bright Cepheids and three semiregular bright supergiants taken with the 1.9-m telescope of the South African Astronomical Observatory. The chemical composition and atmospheric parameters have been determined for S Cru, AP Pup, AX Cir, S TrA, T Cru, R Mus, S Mus, U Car, V382 Car, HD 75276, and R Pup.
Usenko, I. A.; Kniazev, A. Yu.; Berdnikov, L. N.; Kravtsov, V. V.
Masses and Mass Loss Rates of Red Supergiants in Binaries II
NASA Astrophysics Data System (ADS)
We propose to observe all remaining cool, non-interacting supergiant binaries with hot companions from the Parsons & Ake (1998) catalog, satisfying certain feasibility requirements, that were not targets in FUSE program E937, as a Survey and Supplemental Program. The objective is to determine stellar masses of a diverse sample of massive, evolved, late-type stars and their B-type main sequence companions, accurate to 1--2 accurate stellar masses are known for any cool supergiants. An important secondary goal is to determine mass-loss rates of the stellar winds of these evolved stars by observation of wind absorption features superimposed on the hot companions FUV continua. These supergiant binary systems are important, fundamental stellar laboratories useful in verifying and constraining models of stellar structure and evolution. We will proceed by measuring the hot stars radial velocity, preferably at more than one epoch (we will propose continuing observations for FUSE Cycles 7--8). The orbits of the cool supergiant primaries of the target binaries are being accurately determined from the PIs decade-long radial velocity program on the DAO 1.2m McKellar coude telescope. Then the companions velocity amplitude, K_2, can be found from a single radial velocity observation, although multiple observations are preferable. Nevertheless, a single observation will suffice to determine the mass ratio of the stars to 2--4 separated in orbital phase, the accuracy will be 1--2 Some target stars eclipse, and for these accurate stellar masses can be directly obtained. Masses of the remaining stars will be obtained from optical interferometry; these binaries are on the NPOI target list. With the loss of HSTSTIS, bf FUSE is the only available UV spectrograph and therefore, the proposed program is essential to determining fundamental, accurate masses of cool supergiants.
Bennett, K.
The Red and Yellow Supergiants in M33: Kinematics and Massive Star Evolution
NASA Astrophysics Data System (ADS)
Massive star evolution is hard to model, owing to the complications of mass-loss, uncertainties over mixing and convection, the effects of rotation, and so on. It is generally agreed that the most massive stars spend their He-burning lives as Wolf-Rayet stars. Stars of slightly smaller masses spend most of their He-burning phase as red supergiants, after briefly passing through a yellow supergiant phase. We are interested in identifying the numbers and physical properties of these stars throughout the star-forming galaxies of the Local Group in an effort to test stellar evolutionary models at varying metallicities. However, foreground contamination by Milky Way dwarfs is severe for both the yellow supergiants (YSGs) and red supergiants (RSGs). Using the photometry of the Local Group Galaxy Survey, we have used two-color information (B-V vs V-R) to separate likely foreground dwarfs from bona fide RSGs in M33, and obtained radial velocities with Hectospec on the 6.5-m MMT. The radial velocities refine the rotation curves of previous studies, and demonstrate that the rotation curve is quite flat. With the new velocity data we then separate the yellow supergiant population from the foreground using radial velocities as well. Since the number of Wolf-Rayet stars is now known to a few percent in M33 (Neugent et al. 2011, ApJ, in press, as well as poster at this meeting) it is now possible to compare the numbers of RSGs, YSGs, and WRs in this nearby spiral. This work is supported by the National Science Foundation through AST-1008020.
Massey, Philip; Drout, M.; Tokarz, S.; Caldwell, N.
The stellar wind velocity function for red supergiants determined in eclipsing binaries
NASA Technical Reports Server (NTRS)
The potential for direct measurement of the acceleration of stellar winds from the supergiant component of Zeta Aurigae-type binary stars is discussed. The aberration angle of the interaction shock cone centered on the hot star provides a measure of the velocity of the cool star wind at the orbit of the secondary. This is confirmed by direct observations of stellar wind (P Cygni) line profile variations. This velocity is generally smaller than the final (terminal) velocity of the wind, deduced from the P Cygni line profiles. The contrast between these results and previously published supergiant wind models is discussed. The implication on the physics of energy source dissipation predicted in the theoretical models is considered.
Ahmad, Imad A.; Stencel, Robert E.
An analysis of STIS HST UV spectra of M 33 early B supergiants
NASA Astrophysics Data System (ADS)
We present terminal velocities of M 33 B-supergiants, obtained from STIS HST spectra as part of our programme to investigate the Wind Momentum - Luminosity Relationship (WLR) in the Local Group. Terminal velocities are derived from their N V, C Iv, and Si Iv resonance lines in UV spectra. Comparing with IUE spectra of Galactic B-supergiants we found evidence of low metallicity in three of our objects. The terminal velocities are consistent with the corresponding values of Galactic stars, except for B-133. For this star we find a very large vinfty and a red Si Iv component deeper than the blue one, that might be an indication of binarity. The average ratio between terminal and turbulent wind velocities is 0.25, well above the value found for Galactic stars. Partly based on INES data from the IUE satellite.
Urbaneja, M. A.; Herrero, A.; Kudritzki, R. P.; Bresolin, F.; Corral, L. J.; Puls, J.
Discovery of a low mass B[e] supergiant in the SMC.
NASA Astrophysics Data System (ADS)
Peculiar emission-line B supergiants are a group of early-type stars with the following typical characteristics: (a) strong Balmer emission lines frequently with P Cygni profiles, (b) permitted and forbidden lines of FeII, [FeII], [OI], etc. and (c) strong infrared excess possibly due to thermal radiation from circumstellar dust. They represent one of the two main groups of early-type emission line stars in the Magellanic Clouds (MCs). The other group consists of the classical P Cygni stars and their hotter counterparts, Of-like objects. The S Dor variables, also called Hubble-Sandage variables, are the most extreme variables of the P Cygni and Of-like objects (Stahl et al., 1985). The B[e] supergiants are located in the HR diagram in the same region as S Dor variables and represent evolved evolutionary stages of the most luminous and presumably the most massive O stars (Zickgraf et al., 1986).
Heydari-Malayeri, M.
Elemental Abundances in Evolved Supergiants. II. The Young Clusters H and chi Persei
We report on the results of our analyses of high-quality spectra of M supergiants in the h and chi Persei double cluster. Our temperature estimates range from 3500 to 4000 K for a sample of 14 stars. There is a wide range in the lithium abundances, from [Li\\/Fe]=-1.7 to [Li\\/Fe]=-0.10. The 12C\\/13C ratio ranges from 10 to 16 and displays
Guillermo Gonzalez; George Wallerstein
Just One New Measurement of the B[e] Supergiant Hen-S22
NASA Astrophysics Data System (ADS)
This procedure-oriented paper presents a discussion of one new and various archival photometric measurements of the B[e] supergiant Henize-S 22, and outlines significant systematic differences between all involved systems of photometric measurement. The conclusion of this study is that the object is slowly brightening and reddening, a typical signature of an LBV S Doradus phase. The analysis reveals a strong aperture effect in the ASAS photometry of this very special star.
Sterken, C.
The First Stellar Abundance Measurements in the Galactic Center: The M Supergiant IRS 7
NASA Astrophysics Data System (ADS)
The first measurement of the photospheric abundances in a star at the Galactic center are presented. A detailed abundance analysis of the Galactic center M2 supergiant IRS 7 was carried out using high-resolution near-infrared echelle spectra. The Fe abundance for IRS 7 was found to be close to solar, [Fe/H]=-0.02+/-0.13, and nearly identical to the Fe abundance we obtained for the nearby M supergiants ? Ori and VV Cep. Analysis of the first and second overtone lines of CO was used to derive an effective temperature of 3600+/-230 K, a microturbulent velocity of 3.0+/-0.3 km s-1, and a carbon abundance log? (C)=7.78+/-0.13, or [C/H]=-0.77. In addition, we find a high depletion of 0.74+/-0.32 dex in O and an enhancement of 0.92+/-0.18 dex in N. These abundances are consistent with the dredge-up of CNO cycle products but require deep mixing in excess of that predicted by standard models for red supergiants. In light of our measured solar Fe abundance for IRS 7, we discuss other indicators of metallicity at the Galactic center, the interpretation of low-resolution near-infrared spectra of late-type giants and supergiants, including the need for caution in using such spectra as measures of metallicity, and the evolution of massive young stars at the Galactic center. We suggest the possibility that rapid stellar rotation is common for stars formed under conditions in the Galactic center, and that extra internal mixing induced by high rotation rates, rather than evolution at high metallicity, is the explanation for many of the unusual properties of the hot emission-line stars in the Galactic center.
Carr, John S.; Sellgren, K.; Balachandran, Suchitra C.
The Coolest Stars in the Clouds: Unusual Red Supergiants in the Magellanic Clouds
Red supergiants (RSGs) are a He-burning phase in the evolution of moderately\\u000ahigh mass stars (10-25 solar masses). The evolution of these stars,\\u000aparticularly at low metallicities, is still poorly understood. The latest-type\\u000aRSGs in the Magellanic Clouds are cooler than the current evolutionary tracks\\u000aallow, occupying the region to the right of the Hayashi limit where stars are\\u000ano
Emily M. Levesque; Philip Massey; K. A. G. Olsen
The Coolest Stars in the Clouds: Unusual Red Supergiants in the Magellanic Clouds
Red supergiants (RSGs) are a He-burning phase in the evolution of moderately high mass stars (10-25 solar masses). The evolution of these stars, particularly at low metallicities, is still poorly understood. The latest-type RSGs in the Magellanic Clouds are cooler than the current evolutionary tracks allow, occupying the region to the right of the Hayashi limit where stars are no
Emily M. Levesque; Philip Massey; K. A. G. Olsen; Bertrand Plez
Narrow-Band Photometry of Red Supergiants in the Small Magellanic Cloud
A set of 36 red supergiants belonging to the Small Magellanic Cloud have been observed on a six-color narrow-band photometric system that measures continuum points and bands of TiO and CN, all in the near-infrared. The TiO--based spectral types range from R. F. Wing; K. M. Walker; E. Costa; M. L. Houdashelt; D. J. MacConnell 2003-01-01
R. F. Wing; K. M. Walker; E. Costa; M. L. Houdashelt; D. J. MacConnell
The Coolest Stars in the Clouds: Unusual Red Supergiants in the Magellanic Clouds
Red supergiants (RSGs) are a He-burning phase in the evolution of moderately high mass stars (10-25 solar masses). The evolution of these stars, particularly at low metallicities, is still poorly understood. The latest-type RSGs in the Magellanic Clouds are cooler than the current evolutionary tracks allow, occupying the region to the right of the Hayashi limit where stars are no
E. M. Levesque; P. Massey; K. A. G. Olsen; B. Plez
Metallicities and carbon abundances of 40 field red supergiants in the Small Magellanic Cloud
Low-resolution spectra (~5A) for 40 red supergiants in the Small Magellanic Cloud were compared with synthetic spectra, and their metallicities were derived. A mean metallicity of [Fe\\/He]=-0.71 is found for 38 stars cooler than T_eff_<4500K. Using the stellar parameters derived, the carbon abundances were determined by comparing synthetic spectra at the G-band region to the observed spectra. A mean ?(C)=7.85
M. T. Meliani; B. Barbuy; T. Richtler
Scattering of X-rays on the winds of supergiant X-ray binaries
Monte-Carlo simulations of Thomson scattering of X-rays in the stellar wind of OB stars in supergiant X-ray binaries show that at least part of the low-energy excess seen in the X-ray spectra during phases of high absorption can be explained by scattering of X-rays around a dense region in the wind obscuring the direct radiation. In the case of 4U
F. Haberl
Interferometric Studies of Dust Formation in the Red Supergiant Star S Persei
Few methods are as effective as interferometry for probing the dust formation regions around evolved stars at high spatial scales. Using multi-epoch VLBA monitoring observations of 43 GHz SiO (v=1J=1-0) maser emission Ostrowski-Fukuda et al.(2003 AAS meeting 201 poster 115) found that the red supergiant S Persei exhibits clumpy and variable SiO maser spots in a broken elongated (elliptical) ring
R. E. Stencel; C. A. Jurgenson; T. A. Ostrowski-Fukuda
A Transient Supergiant X-Ray Binary in IC�10: An Extragalactic SFXT?
NASA Astrophysics Data System (ADS)
We report the discovery of a large amplitude (factor of ~100) X-ray transient (IC 10 X-2, CXOU J002020.99+591758.6) in the nearby dwarf starburst galaxy IC 10 during our Chandra monitoring project. Based on the X-ray timing and spectral properties, and an optical counterpart observed with Gemini, the system is a high-mass X-ray binary consisting of a luminous blue supergiant and a neutron star. The highest measured luminosity of the source was 1.8 � 1037 erg s�1during an outburst in 2003. Observations before, during, and after a second outburst in 2010 constrain the outburst duration to be less than 3 months (with no lower limit). The X-ray spectrum is a hard power law (? = 0.3) with fitted column density (NH = 6.3 � 1021 atom cm�2), consistent with the established absorption to sources in IC 10. The optical spectrum shows hydrogen Balmer lines strongly in emission at the correct blueshift (-340 km s�1) for IC 10. The N III triplet emission feature is seen, accompanied by He II [4686] weakly in emission. Together these features classify the star as a luminous blue supergiant of the OBN subclass, characterized by enhanced nitrogen abundance. Emission lines of He I are seen, at similar strength to H?. A complex of Fe II permitted and forbidden emission lines are seen, as in B[e] stars. The system closely resembles galactic supergiant fast X-ray transients, in terms of its hard spectrum, variability amplitude, and blue supergiant primary.
Laycock, Silas; Cappallo, Rigel; Oram, Kathleen; Balchunas, Andrew
Galactovertical Oscillations of Blue Supergiants as a Test of the Theories of Stellar Evolution
NASA Astrophysics Data System (ADS)
The absolute magnitudes, intrinsic colours, and distances are inferred for 619 Galactic blue supergiants using published UBV or uvby and H? photometry and absolute-magnitude and intrinsic-colour calibrations by Dambis (1990, 1991). The individual ages are determined for all stars based on different isochrone grids both classical and those including mass loss and overshooting. The vertical scale height of the subsample of blue supergiants located within 1.5 kpc of the Sun (a total of 226 stars) is found to decrease with the age from ~ 60 pc for the youngest stars down to ~ 20 pc for the oldest ones. The time scale of this decrease is known to be related to the period of galactovertical oscillations in the solar neighbourhood (M. Joeveer, Tartu Publ., 1974, vol. 47, p. 35). The latter can be independently inferred from the known mean density in the solar neighbourhood and Oort's constants and then compared with the values implied by the analysis of the evolution of the Galactovertical distribution of blue supergiants in terms of various isochrone grids in order to test the underlying theories of stellar evolution. Our results provide strong evidence in favor of classical theories of stellar evolution without overshooting and intense mass loss.
Dambis, A. K.
Evidence for Tidal Heating in the Dynamics of LMC Carbon Stars and Red Supergiants
NASA Astrophysics Data System (ADS)
We present an analysis of the kinematics of the HI gas, carbon stars, and red supergiants of the Large Magellanic Cloud. After correcting the line-of-sight velocities for the recent accurate measurement of the LMC's space motion, we find that each kinematic tracer clearly defines a flat rotation curve with similar shape but different amplitude for each tracer: 61 km s-1 for the carbon stars, 80 km s-1 for the HI gas, and 107 km s-1 for the red supergiants. We suggest that noncircular motions of the stars and gas in the LMC can at least in part explain the different rotation amplitudes. A significant fraction, 7-15%, of the total sample of carbon stars appears to be associated with previously identified tidal HI streamers. In addition, although the local velocity dispersion of the red supergiants is small, 8 km s-1, their velocity dispersion about the carbon star rotation solution is 17 km s-1, equal to the velocity dispersion of the carbon stars themselves. We thus appear to be witnessing the tidal heating of the LMC's stellar populations.
Olsen, Knut A.; Massey, P.
Spectral atlas of O9.5-A1-Type supergiants
NASA Astrophysics Data System (ADS)
High-resolution spectra of nine supergiants and three comparison stars taken with CCD echelle spectrographs in the coude� foci of the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and 2-m telescope of Terskol Observatory (with R = 40000 and R = 45000, respectively) are reported in a tabular and graphic form. Two hundred ( ? Cam, O9.5 Ia) to 1000 (HD 12953, A1 Ia-0) stellar and interstellar lines and bands are identified in the 3600 7800 �� wavelength interval and most of them have their central intensities and heliocentric radial velocities measured. A spectral classification based on weak photospheric absorptions is tested. This is actual for the brightest supergiants and hypergiants, where the formation regions of strong lines, which are traditionally used for classification, also include the bases of stellar winds. Radial gradients of velocity are revealed in the atmospheres of supergiants. The cases of the refinement of the effective wavelengths, analysis of blends, and revealing of wind anomalies in line profiles are illustrated. The atlas is used extensively as a teaching tool.
Chentsov, E. L.; Sarkisyan, A. N.
On the H? behaviour of blue supergiants: rise and fall over the bi-stability jump
NASA Astrophysics Data System (ADS)
Context. The evolutionary state of blue supergiants is still unknown. Stellar wind mass loss is one of the dominant processes determining the evolution of massive stars, and it may provide clues to the evolutionary properties of blue supergiants. As the H? line is the most oft-used mass-loss tracer in the OB-star regime, we investigate H? line formation as a function of Teff. Aims: We provide a detailed analysis of the H? line for OB supergiant models over an Teff range between 30 000 and 12 500 K, with the aim of understanding the mass-loss properties of blue supergiants. Methods: We model the H? line using the non-LTE code cmfgen, in the context of the bi-stability jump at Teff ~ 22 500 K. Results: We find a maximum in the H? equivalent width at 22 500 K exactly at the location of the bi-stability jump. The H? line-profile behaviour is characterised by two branches of effective temperature: (i) a hot branch between 30 000 and 22 500 K, where H? emission becomes stronger with decreasing Teff; and (ii) a cool branch between 22 500 and 12 500 K, where the H? line becomes weaker. Our models show that this non-monotonic H? behaviour is related to the optical depth of Ly?, finding that at the "cool" branch the population of the 2nd level of hydrogen is enhanced in comparison to the 3rd level. This is expected to increase line absorption, leading to weaker H? flux when Teff drops from 22 500 K downwards. We also show that for late B supergiants (at Teff below ~15 000 K), the differences in the H? line between homogeneous and clumpy winds becomes insignificant. Moreover, we show that, at the bi-stability jump, H? changes its character completely, from an optically thin to an optically thick line, implying that macro-clumping should play an important role at temperatures below the bi-stability jump. This would not only have consequences for the character of observed H? line profiles, but also for the reported discrepancies between theoretical and empirical mass-loss rates.
Petrov, Blagovest; Vink, Jorick S.; Gr�fener, G�tz
Lithium abundance in atmospheres of F- and G-type supergiants and bright giants
NASA Astrophysics Data System (ADS)
Lithium in the atmosphere of a F or G supergiant reflects the initial Li abundance and the internal history of the star. During evolution of a star from the main sequence (MS) to the supergiant phase, lithium may be destroyed by, for example, rotationally induced mixing in the MS stars and strongly diluted by development of the supergiant's convective envelope. In order to probe the connection between atmospheric Li abundance and evolutionary predictions, we present a non-local thermodynamic equilibrium abundance analysis of the resonance doublet Li I at 6707.8 � for 55 Galactic F and G supergiants and bright giants (we observed 43 of them, the remaining 12 are added from Luck and Wepfer's list). The derived lithium abundances log ?(Li) may be considered in three groups, namely: (i) 10 Li-rich giants with log ?(Li) = 2.0-3.2 (all 10 are F-type or A9 stars); (ii) 13 G- to K0-type stars with Li abundances in the narrow range log ?(Li) = 1.1-1.8; (iii) all other stars provide just upper limits to the Li abundance. The derived Li abundances are compared with theoretical predictions of 2-15 M? stars (both rotating and non-rotating). Our results are generally in good agreement with theory. In particular, the absence of detectable lithium for the majority of programme stars is explainable. The comparison suggests that the stars may be separated by mass M into two groups, namely M ? 6 M? and M > 6 M?. All Li-rich giants and supergiants with log ?(Li) ? 2.0 have masses M < 6 M?; this conclusion follows not only from our work but also from a scrutiny of published data. 11 of 13 stars with log ?(Li) = 1.1-1.8, specifically the stars with M < 6 M?, show good agreement with the post-first dredge-up surface abundance log ?(Li) ? 1.4 predicted for the non-rotating 2-6 M? stellar models. An absence of Li-rich stars in the range M > 6 M? agrees with the theoretical prediction that F and G supergiants and giants with M > 6 M? cannot show detectable lithium. We note that present theory appears unable to account for the derived Li abundances for some stars, namely for (i) a few relatively low-mass Li-rich giants (M < 6 M?), whose high Li abundances accompanied by rather high rotational velocities or substantial nitrogen excess contradict theoretical predictions; (ii) the relatively high-mass supergiants HR 461 and HR 8313 (M > 6 M?) with the detected abundances log ? = 1.3-1.5. It is possible that the lithium in such stars was synthesized recently.
Lyubimkov, Leonid S.; Lambert, David L.; Kaminsky, Bogdan M.; Pavlenko, Yakov V.; Poklad, Dmitry B.; Rachkovskaya, Tamara M.
X-ray pulsations from the region of the supergiant fast X-ray transient IGR J17544-2619
NASA Astrophysics Data System (ADS)
Phase-targeted RXTE observations have allowed us to detect a transient 71.49 � 0.02 s signal that is most likely to be originating from the supergiant fast X-ray transient IGR J17544-2619. The phase-folded light curve shows a possible double-peaked structure with a pulsed flux of ~4.8 � 10-12 erg cm-2 s-1 (3-10 keV). Assuming the signal to indicate the spin period of the neutron star in the system, the provisional location of IGR J17544-2619 on the Corbet diagram places the system within the classical wind-fed supergiant XRB region. Such a result illustrates the growing trend of supergiant fast X-ray transients to span across both of the original classes of HMXB in Porb - Pspin space.
Drave, S. P.; Bird, A. J.; Townsend, L. J.; Hill, A. B.; McBride, V. A.; Sguera, V.; Bazzano, A.; Clark, D. J.
The Discovery of a Massive Cluster of Red Supergiants with GLIMPSE
NASA Astrophysics Data System (ADS)
We report the discovery of a previously unknown massive Galactic star cluster at ell = 29fdg22, b = -0fdg20. Identified visually in mid-IR images from the Spitzer GLIMPSE survey, the cluster contains at least eight late-type supergiants, based on follow-up near-IR spectroscopy, and an additional 3-6 candidate supergiant members having IR photometry consistent with a similar distance and reddening. The cluster lies at a local minimum in the 13CO column density and 8 ?m emission. We interpret this feature as a hole carved by the energetic winds of the evolving massive stars. The 13CO hole seen in molecular maps at V LSR ~ 95 km s-1 corresponds to near/far kinematic distances of 6.1/8.7 � 1 kpc. We calculate a mean spectrophotometric distance of 7.0+3.7 -2.4 kpc, broadly consistent with the kinematic distances inferred. This location places it near the northern end of the Galactic bar. For the mean extinction of AV = 12.6 � 0.5 mag (AK = 1.5 � 0.1 mag), the color-magnitude diagram of probable cluster members is well fit by isochrones in the age range 18-24 Myr. The estimated cluster mass is ~20,000 M sun. With the most massive original cluster stars likely deceased, no strong radio emission is detected in this vicinity. As such, this red supergiant (RSG) cluster is representative of adolescent massive Galactic clusters that lie hidden behind many magnitudes of dust obscuration. This cluster joins two similar RSG clusters as residents of the volatile region where the end of our Galaxy's bar joins the base of the Scutum-Crux spiral arm, suggesting a recent episode of widespread massive star formation there.
Alexander, Michael J.; Kobulnicky, Henry A.; Clemens, Dan P.; Jameson, Katherine; Pinnick, April; Pavel, Michael
Swift Optimized Strategy for Supergiant Fast X-ray Transients Study
NASA Astrophysics Data System (ADS)
Supergiant Fast X-ray Transients (SFXTs) are HMXBs with OB supergiant companions and are known for hour-long X-ray outbursts characterized by 3-5 orders of magnitude luminosity increases. Our Swift Supergiant Fast X-ray Transients Project, active since 2007, has taken advantage of Swift's flexible scheduling for a systematic investigation on both the SFXT bright flares which triggered the Burst Alert Monitor (BAT) with fast X-Ray Telescope (XRT) follow-up (1-2 min repointing time), and the emission outside the bright outbursts with XRT regular monitoring of several SFXTs and candidates with 2-3 observations per week (1-2 ks) for at least one year per source. This has allowed us to study for the first time broadband spectra of SFXT outbursts, to prove that timescales of source activity during outburts are of the order of weeks, to determine long-term properties of SFXTs, and to obtain an assessment of the fraction of the time these sources spend in each luminosity phase (outbursts, intermediate level, and quiescence) and their duty cycle of inactivity by means of very sensitive and non-serendipitous observations. We summarize the results achieved to date with our observing strategy and focus on the time resolved broadband spectral analysis of the 2011 and 2013 Swift detected outbursts of IGR J08408-4503, carried out with different spectral models, including the COMPMAG model specifically dedicated to the physical framework of accretion at the polar cap of a neutron star with a high magnetic field (>= 1E12 G), expected to be typical of these accreting systems.
Mangano, Vanessa; Romano, P.; Kennea, J. A.; Vercellone, S.; Burrows, D. N.; Ducci, L.; Esposito, P.; Krimm, H. A.; Barthelmy, S. D.; Gehrels, N.; Swift
Spatially-resolved high-spectral resolution observations of the red supergiant Betelgeuse
NASA Astrophysics Data System (ADS)
Red supergiants (RSGs) experience slow, intensive mass loss up to 10-4 M? yr-1. Despite its importance not only in stellar evolution but also in the chemical enrichment of the interstellar matter, the mass loss mechanism in RSGs is not well understood. A better understanding of the outer atmosphere of RSGs is a key to unraveling the mass-loss mechanism in these stars. High spatial resolution observations in IR molecular lines are very effective for probing the physical properties of the inhomogeneous outer atmosphere. We observed the prototypical RSG Betelgeuse (M1-2Ia-Ibe) in the CO first overtone lines with the spectro-interferometric instrument AMBER at the ESO's Very Large Telescope Interferometer (VLTI) using baselines of 16, 32, and 48 m. Details of the observations and the modeling are described in Ohnaka et al. (2009). The high-spectral (R = 4800-12000) and high-spatial resolution (9 mas) provided with AMBER allowed us to study inhomogeneities seen in the individual CO first overtone lines. Our AMBER observations represent the highest spatial resolution achieved for Betelgeuse, corresponding to five resolution elements over its stellar disk. The AMBER visibilities and closure phases in the K-band continuum can be reasonably fitted by a uniform disk with a diameter of 43.19 � 0.03 mas or a limb-darkening disk with 43.56 � 0.06 mas and a limb-darkening parameter of (1.2 � 0.07) � 10-1. On the other hand, our AMBER data in the CO lines reveal salient inhomogeneous structures. The visibilities and phases (closure phases, as well as differential phases representing asymmetry in lines with respect to the continuum) measured within the CO lines show that the blue and red wings originate in spatially distinct regions over the stellar disk, indicating an inhomogeneous velocity field that makes the star appear different in the blue and red wings. Our AMBER data in the CO lines can be roughly explained by a simple model, in which a patch of CO gas is moving outward or inward with velocities of 10-15 km s-1, while the CO gas in the remaining region in the atmosphere is moving in the opposite direction at the same velocities. These velocities compare favorably with the macroturbulent velocities of 10-20 km s-1 derived by spectroscopic analyses. Also, the AMBER data are consistent with the presence of warm molecular layers (so-called MOLsphere) extending to ~1.4-1.5 R* with a CO column density of ~ 1 � 1020 cm-2. However, the present data are insufficient to constrain the surface pattern uniquely or to reconstruct an image. Our AMBER observations of Betelgeuse are the first spatially resolved study of the macroturbulence in a stellar atmosphere (photosphere and possibly MOLsphere as well) other than the Sun. The spatially resolved CO gas motion is likely to be related to convective motion in the upper atmosphere or intermittent mass ejections in clumps or arcs.
Ohnaka, K.
Temperature, gravity, and bolometric correction scales for non-supergiant OB stars
NASA Astrophysics Data System (ADS)
Context. Precise and accurate determinations of the atmospheric parameters effective temperature and surface gravity are mandatory to derive reliable chemical abundances in OB stars. Furthermore, fundamental parameters like distances, masses, radii, luminosities can also be derived from the temperature and gravity of the stars. Aims: Atmospheric parameters recently determined at high precision with several independent spectroscopic indicators in non-local thermodynamic equilibrium, with typical uncertainties of ~300 K for temperature and of ~0.05 dex for gravity, are employed to calibrate photometric relationships. This is in order to investigate whether a faster tool to estimate atmospheric parameters can be provided. Methods: Temperatures and gravities of 30 calibrators, i.e. well-studied OB main sequence to giant stars in the solar neighbourhood, are compared to reddening-independent quantities of the Johnson and Str�mgren photometric systems, assuming normal reddening. In addition, we examine the spectral and luminosity classification of the star sample and compute bolometric corrections. Results: Calibrations of temperatures and gravities are proposed for various photometric indices and spectral types. Once the luminosity of the stars is well known, effective temperatures can be determined at a precision of ~400 K for luminosity classes III/IV and ~800 K for luminosity class V. Furthermore, surface gravities can reach internal uncertainties as low as ~0.08 dex when using our calibration to the Johnson Q-parameter. Similar precision is achieved for gravities derived from the ?-index and the precision is lower for both atmospheric parameters when using the Str�mgren indices [c1] and [u - b] . In contrast, external uncertainties are larger for the Johnson than for the Str�mgren calibrations. Our uncertainties are smaller than typical differences among other methods in the literature, reaching values up to � 2000 K for temperature and � 0.25 dex for gravity, and in extreme cases, + 6000 K and � 0.4 dex, respectively. A parameter calibration for sub-spectral types is also proposed. Moreover, we present a new bolometric correction relation to temperature based on our empirical data, rather than on synthetic grids. Conclusions: The photometric calibrations presented here are useful tools to estimate effective temperatures and surface gravities of non-supergiant OB stars in a fast manner. This is also applicable to some single-line spectroscopic binaries, but caution has to be taken for undetected double-lined spectroscopic binaries and single objects with anomalous reddening-law, dubious photometric quantities and/or luminosity classes, for which the systematic uncertainties may increase significantly. We recommend to use these calibrations only as a first step of the parameter estimation, with subsequent refinements based on spectroscopy. A larger sample covering more uniformly the parameter space under consideration will allow refinements to the present calibrations. Based on observations collected at the Centro Astron�mico Hispano Alem�n (CAHA) at Calar Alto, operated jointly by the Max- Planck Institut f�r Astronomie and the Instituto de Astrof�sica de Andaluc�a (CSIC), proposals H2001-2.2-011 and H2005-2.2-016.Based on observations collected at the European Southern Observatory, Chile, ESO 074.B-0455(A) and from the ESO Archive.Based on spectral data retrieved from the ELODIE archive at Observatoire de Haute-Provence (OHP).Appendices A and B are available in electronic form at http://www.aanda.org
Nieva, M.-F.
Evolutionary Status of the Peculiar B3IA Supergiant HD 157038
NASA Astrophysics Data System (ADS)
HD157038 is a peculiar hot supergiant whose spectrum shows evidence of having been contaminated by the products of interior nuclear reactions. In particular, visible region observations (e.g. Walborn 1976, Lennon and Dufton 1985) indicate that nitrogen enrichment of the stellar atmosphere appears to have occurred. This proposal aims to extend our observations of this star into the UV to confirm our previous findings, to investigate the current mass loss rate from this star, and to obtain an estimate of the stellar mass. We propose to observe this star continuously for one NASA and one ESA shift.
Nichols-Bohlin, Joy
X-ray scanning a supergiant wind-accretor: eclipse egress in Vela X-1
NASA Astrophysics Data System (ADS)
We propose to use one XMM-Newton orbit observing the eclipse egress and early post-eclipse phase of the Vela~X-1/HD~77581 binary system. We plan to use EPIC-pn CCD spectra and pulse profiles together with RGS results for emission lines in order to study in unprecedented detail the emerging neutron star's emission and measure the scale height of the supergiant's extended atmosphere with high accuracy. Small time scale variations in the observed column density will track clumps in the lower stellar wind.
Kretschmar, Peter
Spectroscopic and Temporal Properties of Supergiant Fast X-ray Transients with Swift
NASA Astrophysics Data System (ADS)
We present a review of the Swift Supergiant Fast X-ray Transients (SFXT) project. Swift has recently opened a brand new way of investigating this class of High-Mass X-ray Binaries whose optical counterparts are O or B supergiant stars, and whose X-ray outbursts are about 4 orders of magnitude brighter than the quiescent state. Thanks to its scheduling flexibility, Swift has allowed us to regularly monitor a small sample of SFXTs with 2-3 observations per week (1-2 ks) with the X-Ray Telescope (XRT) over their entire visibility period (9 months/year) for over 2 years. This intense monitoring has allowed us to study them throughout all phases of their lives (outbursts, intermediate level, and quiescence) and to determine the long-term properties and their duty cycles, through very sensitive and non-serendipitous observations. We also monitored one source along its whole orbital period. Furthermore, thanks to its autonomous and rapid repointing, Swift has allowed us for the first time to catch and study, from optical to hard X-ray, the bright outbursts, and to follow them in the X-ray for days, thus determining the actual duration of the outburst episodes and the shape of their X-ray spectra through simultaneous broadband spectroscopy. We acknowledge financial contribution from the agreement ASI-INAF I/009/10/0.
Romano, Patrizia; Kennea, J. A.; Vercellone, S.; Burrows, D. N.; Cusumano, G.; Esposito, P.; Farinelli, R.; Krimm, H. A.; La Parola, V.; Mangano, V.; Pagani, C.; Gehrels, N.
A critical test of empirical mass loss formulas applied to individual giants and supergiants
NASA Astrophysics Data System (ADS)
To test our new, improved Reimers-type mass-loss relation, given by Schr�der & Cuntz in 2005 (ApJ, 630, L73), we take a look at the best studied galactic giants and supergiants - particularly those with spatially resolved circumstellar shells and winds, obtained directly or by means of a companion acting as a probing light source. Together with well-known physical parameters, the selected stars provide the most powerful and critical observational venues for assessing the validity of parameterized mass-loss relations for cool winds not driven by molecules or dust. In this study, star by star, we compare our previously published relation with the original Reimers relation (1975, Mem. Roy. Soc. Li�ge 6. Ser. 8, 369), the Lamers relation (1981, ApJ, 245, 593), and the two relations by de Jager and his group (1988, A&AS, 72, 259; 1990, A&A, 231, 134). The input data, especially the stellar masses, have been constrained using detailed stellar evolution models. We find that only the relationship by Schr�der & Cuntz agrees, within the error bars, with the observed mass-loss rates for all giants and supergiants.
Schr�der, K.-P.; Cuntz, M.
The Fundamental Parameters and Chromospheric Structure of the M Supergiant VV Cephei
NASA Astrophysics Data System (ADS)
The long-period binary VV Cephei (M2 Iab + B0-2, V=4.9, P=20.34 yr) is the brightest M supergiant eclipsing binary in the sky. The M star primary is a close spectral match to that of Betelgeuse. In the ultraviolet (UV), the early B-type hot companion dominates the spectrum, and as the system emerges from eclipse, the line of sight to the B star probes deep into the outer atmosphere (the "chromosphere") of the M supergiant. The UV spectrum of VV Cep has been observed from total eclipse (in 1997-98) through quadrature (2002) and periastron (2005) at a total of 22 epochs, 20 of these using STIS high-resolution ( 100,000) ultraviolet spectroscopy from the Hubble Space Telescope, and two with the Far Ultraviolet Spectroscopic Explorer satellite. I will present a brief overview of spectrum formation in the system, and focus on the subset of the STIS observations (those immediately following the egress from totality) that probed the chromosphere of VV Cephei. From these observations, I have constructed a spatially-resolved empirical model chromosphere that includes the temperature, density, velocity, and ionization structure of the outer atmosphere of VV Cep above the classical photosphere. I will present these results, and also constraints on the fundamental stellar and orbital parameters provided by these UV observations.
Bennett, Philip D.
Wind variability in the Large Magellanic Cloud B(e) supergiant HD 34664
NASA Technical Reports Server (NTRS)
We present optical linear spectropolarimetry of the B(e) supergiant HD 34664. The polarization and position angle display significant spectral features which correspond to the H-alpha and H-beta emission lines. We use the line polarizations to separate the interstellar foreground polarization from the intrinsic polarization of HD 34664. The intrinsic polarization is consistent with electron scattering in a circumstellar disk seen at high inclination and provides further and independent evidence for the two-component wind model of the B(e) supergiants. We compare the polarization and spectrum of HD 34664 to observations published in the literature. In our data the continuum polarization is by a factor of two larger and the H-alpha line-to-continuum ratio is by a factor of at least four increased over previous observations. Since both the polarization and the line intensity are measures of the electron density in the stellar wind, we suggest that the observed variations can be attributed to a rise in the stellar mass-loss rate.
Schulte-Ladbeck, R. E.; Clayton, G. C.
The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought
NASA Astrophysics Data System (ADS)
We use moderate-resolution optical spectrophotometry and the new MARCS stellar atmosphere models to determine the effective temperatures of 74 Galactic red supergiants (RSGs). The stars are mostly members of OB associations or clusters with known distances, allowing a critical comparison with modern stellar evolutionary tracks. We find we can achieve excellent matches between the observations and the reddened model fluxes and molecular transitions, although the atomic lines Ca I ?4226 and Ca II H and K are found to be unrealistically strong in the models. Our new effective temperature scale is significantly warmer than those in the literature, with the differences amounting to 400 K for the latest type M supergiants (i.e., M5 I). We show that the newly derived temperatures and bolometric corrections give much better agreement with stellar evolutionary tracks. This agreement provides a completely independent verification of our new temperature scale. The combination of effective temperature and bolometric luminosities allows us to calculate stellar radii; the coolest and most luminous stars (KW Sgr, Case 75, KY Cyg, HD 206936=? Cep) have radii of roughly 1500 Rsolar (7 AU), in excellent accordance with the largest stellar radii predicted from current evolutionary theory, although smaller than that found by others for the binary VV Cep and for the peculiar star VY CMa. We find that similar results are obtained for the effective temperatures and bolometric luminosities using only the dereddened V-K colors, providing a powerful demonstration of the self-consistency of the MARCS models.
Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges
CCD Spectroscopy of New M-Type Supergiants in the Southern Milky way
NASA Astrophysics Data System (ADS)
We are obtaining COD spectra of possible new M supergiants identified on low-dispersion, I-N objective-prism plates taken near the southern galactic plane. The spectra cover the range 6400-8800 � with a resolution of 8 �. The spectra of 180 stars have been observed at least once, and the spectra of about 40 late-type,. luminous MK standards have been obtained as well. The standards are used to calibrate equivalent widths of the Ca II triplet as a function of luminosity and temperature, and this is the principal criterion used to classify the COD spectra. Analysis of this material indicates that there are >60 new K/M super- giants, some very heavily reddened, and a few new S stars in the sample. This at least doubles the number of late supergiants known in the areas searched. We expect that some of these stars lie at distances of 5 to 6 kpc and that the survey will have a significant impact on studies of galactic structure and massive star evolution
MacConnell, D. J.; Wing, R. F.; Costa, E.
The 100-month Swift Catalogue of Supergiant Fast X-ray Transients
NASA Astrophysics Data System (ADS)
The 100-month Swift Catalogue of Supergiant Fast X-ray Transients, collects over a thousand Swift/BAT flares from 11 Supergiant Fast X-ray Transients (SFXTs), and is complete down to fluxes of about 6x1E-10 erg/cm2/s (daily timescale) and about 1.5x1E-9 erg/cm2/s (orbital timescale, averaging about 800 s) in the 15-150 keV energy band. These hard X-ray flares typically last a few hundred seconds, reach fluxes in excess of 100 mCrab (15-50 keV), and last much less than a day. Their clustering in orbital phase-space,however, demonstrates that the outbursts are a much longer phenomenon, lasting up to a few days, as previously observed in deeper Swift soft X-ray observations. This large dataset is used to probe the properties of the high and intermediate emission states in SFXTs, and to infer the properties of these binary systems, as well as to estimate the number of flares per year each source is likely to produce as a function of the detection threshold and limiting flux. We also present preliminary results from our analysis of spectral evolution-dependent flux light curves and broad-band spectroscopy of the outbursts.
Romano, Patrizia; Krimm, Hans A.; Palmer, David; Ducci, Lorenzo; Esposito, Paolo; Vercellone, Stefano; Evans, Phil; Guidorzi, Cristiano; Mangano, Vanessa; Kennea, Jamie A; Barthelmy, Scott Douglas; Burrows, David N.; Gehrels, Neil
Analysis of A-F Supergiants in M31 from Keck HIRES Spectroscopy
NASA Astrophysics Data System (ADS)
The first stellar abundances in M31 are presented, based on Keck I HIRES spectroscopy and model atmospheres analyses of three A-F supergiants, 41-2368, 41-3712, and A-207. We find that the stellar oxygen abundances are in good agreement with those determined from nebular studies, even though the stars do NOT show a clear radial gradient in oxygen. The uncertainties in the stellar abundances are smaller than the range in the nebular results, making these stars ideal objects for further studies of the distribution of oxygen in M31. We show that the stars can be used to study the abundance distributions of other elements as well, including iron-group and heavier elements. The A-F supergiants also provide direct information on the metallicity and reddening of nearby Cepheid stars. We have examined the metallicity and reddening assumptions used for Cepheids within 1' of our targets and noted differences from values used in the literature. This work has recently been submitted to the Astrophysical Journal.
Venn, K. A.; McCarthy, J. K.; Lennon, D. J.; Przybilla, N.; Kudritzki, R. P.; Lemke, M.
Analysis of Four A-F Supergiants in M31 from Keck HIRES Spectroscopy
NASA Astrophysics Data System (ADS)
The first stellar abundances in M31 are presented, based on Keck I HIRES spectroscopy and model atmospheres analyses of three A-F supergiants, 41-2368, 41-3712, and A-207. We also present the preliminary analysis of a fourth star, 41-3654. We find that the stellar oxygen abundances are in good agreement with those determined from nebular studies, even though the stars do not show a clear radial gradient in oxygen. The uncertainties in the stellar abundances are smaller than the range in the nebular results, making these stars ideal objects for further studies of the distribution of oxygen in M31. We show that the stars can be used to study the abundance distributions of other elements as well, including iron-group and heavier elements. The A-F supergiants also provide direct information on the metallicity and reddening of nearby Cepheid stars. We have examined the metallicity and reddening assumptions used for Cepheids within 1' of our targets and noted the differences from values used in the literature. Based on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
Venn, K. A.; McCarthy, J. K.; Lennon, D. J.; Przybilla, N.; Kudritzki, R. P.; Lemke, M.
Spectroscopic observations of AB-supergiants in M 31 and M 33
NASA Astrophysics Data System (ADS)
We have observed a number of the most luminous A and B supergiants in the galaxies M 31 and M 33 at intermediate dispersion obtaining both blue and red spectrograms. We have determined spectral types and luminosity classifications from these data, in a few cases revising previous evaluations. From comparison with galactic analogues we estimate approximate metallicities for M 31 and M 33. In addition, for the first time we present Halpha_ profiles for these stars which we use to estimate mass loss rates. We conclude that M 31 is comparable in metallicity to our galaxy but M 33 is slightly deficient, more precise estimates requiring higher resolution data. The Halpha_ data are morphologically similar to those of galactic stars and clearly contradict claims that mass-loss rates for luminous stars in M 31 are up to a factor of ten less than their galactic counterparts. We note in particular that the M 31 star 40-1939 is confirmed here as a B1Ia^+^ hypergiant rather than an O6I supergiant (Hutchings et al. 1987) thus explaining the absence of typical wind features associated with an O6 classification. Also of particular interest are the luminous A-hypergiants in M 33, B324 especially appears to be more luminous than any comparable star in our galaxy or the Magellanic Clouds, has an Halpha_ equivalent width of 40A in emission and exhibits a number of FeII P-Cygni profiles.
Herrero, A.; Lennon, D. J.; Vilchez, J. M.; Kudritzki, R. P.; Humphreys, R. H.
A significant fraction of massive stars are moving supersonically through the interstellar medium (ISM), either due to disruption of a binary system or ejection from their parent star cluster. The interaction of their wind with the ISM produces a bow shock. In late evolutionary stages these stars may undergo rapid transitions from red to blue and vice versa on the Hertzsprung-Russell diagram, with accompanying rapid changes to their stellar winds and bow shocks. Recent three-dimensional simulations of the bow shock produced by the nearby runaway red supergiant (RSG) Betelgeuse, under the assumption of a constant wind, indicate that the bow shock is very young (<30, 000 years old), hence Betelgeuse may have only recently become an RSG. To test this possibility, we have calculated stellar evolution models for single stars which match the observed properties of Betelgeuse in the RSG phase. The resulting evolving stellar wind is incorporated into two-dimensional hydrodynamic simulations in which we model a runaway blue supergiant (BSG) as it undergoes the transition to an RSG near the end of its life. We find that the collapsing BSG wind bubble induces a bow shock-shaped inner shell around the RSG wind that resembles Betelgeuse's bow shock, and has a similar mass. Surrounding this is the larger-scale retreating bow shock generated by the now defunct BSG wind's interaction with the ISM. We suggest that this outer shell could explain the bar feature located (at least in projection) just in front of Betelgeuse's bow shock.
Mackey, Jonathan; Mohamed, Shazrene; Neilson, Hilding R.; Langer, Norbert; Meyer, Dominique M.-A., E-mail: email@example.com [Argelander-Institut fuer Astronomie, Auf dem Huegel 71, D-53121 Bonn (Germany)
IUE observations of the Henize-Carlson sample of peculiar emission line supergiants: The galactic analogs of the Magellanic Zoo
NASA Technical Reports Server (NTRS)
Some 15 stars from the Carlson-Henize survey of southern peculiar emission line stars were studied. From both the optical and UV spectra, they appear to be galactic counterparts of the most extreme early-type emission line supergiants of the Magellanic Clouds.
Shore, Steven N.; Brown, Douglas N.; Sanduleak, N.
A hot companion to Mu Sagittarii - An opportunity to sound the atmosphere of a B8 Ia supergiant
NASA Technical Reports Server (NTRS)
It is argued that the bright supergiant star Mu Sagittarii is accompanied by a smaller and hotter star, of spectral type approximately B1.5 V. The single-line radial-velocity curve of the B8 star leads to a fairly large mass function, f(m) = 2.64 solar masses, implying that the companion should have at least 50 percent of the mass of the visible star. Older optical observations indicated the presence of a shallow eclipse at the time of the conjunction with the supergiant behind the companion. Since the Copernicus, IUE, and Voyager observations show that the companion is the hotter component, that eclipse must have been the secondary eclipse (if it was an eclipse at all). A deeper, primary eclipse has been predicted by Plavec in 1978. It was indeed observed as a marked decrease of the far-ultraviolet flux from the system both with the Copernicus and the IUE satellites. The presence of a hotter but smaller component in Mu Sagittarii offers a unique opportunity to study the outer atmospheric layers of a supergiant which is of a much earlier spectral type than the supergiants in the Zeta Aurigae systems.
Polidan, R. S.; Plavec, M. J.
The progenitors of Type IIP supernovae (SNe) have an apparent upper limit to their initial masses of about 20 M{sub Sun }, suggesting that the most massive red supergiants evolve to warmer temperatures before their terminal explosion. But very few post-red supergiants are known. We have identified a small group of luminous stars in M31 and M33 that are candidates for post-red supergiant evolution. These stars have A-F-type supergiant absorption line spectra and strong hydrogen emission. Their spectra are also distinguished by the Ca II triplet and [Ca II] doublet in emission formed in a low-density circumstellar environment. They all have significant near- and mid-infrared excess radiation due to free-free emission and thermal emission from dust. We estimate the amount of mass they have shed and discuss their wind parameters and mass loss rates, which range from a few Multiplication-Sign 10{sup -6} to 10{sup -4} M{sub Sun} yr{sup -1}. On an H-R diagram, these stars will overlap the region of the luminous blue variables (LBVs) at maximum light; however, the warm hypergiants are not LBVs. Their non-spherical winds are not optically thick, and they have not exhibited any significant variability. We suggest, however, that the warm hypergiants may be the progenitors of the ''less luminous'' LBVs such as R71 and even SN1987A.
Humphreys, Roberta M.; Davidson, Kris; Grammer, Skyler; Kneeland, Nathan [Minnesota Institute for Astrophysics, 116 Church Street SE, University of Minnesota, Minneapolis, MN 55455 (United States); Martin, John C. [University of Illinois, Springfield, IL (United States); Weis, Kerstin; Burggraf, Birgitta, E-mail: email@example.com [Astronomical Institute, Ruhr-Universitaet Bochum (Germany)
Model-atmosphere analysis of high-dispersion spectra of four red giants and supergiants
NASA Astrophysics Data System (ADS)
A model atmosphere analysis of three cool giants (? Cet, ? Tau, ? TrA) and one supergiant (? Peg) is presented. One of the principal reasons for the analysis being the search for possible non-LTE effects, the measured lines are split into high excitation lines and low excitation lines in order to test the sensitivity of the ionization balance method against deviations from LTE. Even though for iron no pronounced split can be found to occur, other elements, e.g. Mn and Ni, hint at the existence of deviations from LTE in cool giant stars. Deviations from the solar abundance pattern are found for the elements of medium atomic number. Two of the stars (? TrA and ? Peg) display over-abundances in barium.
Kovacs, N.
IUE observations of HR 6902 - Effect of luminosity on supergiant chromospheres
NASA Technical Reports Server (NTRS)
IUE observations of the most recently discovered Zeta Aurigae system, HR 6902, are reported to reveal profound differences in the spectrum of the chromosphere of the cool primary from those of all other Zeta Aurigae systems. Unlike its sister systems, HR 6902 shows evidence of neither strong wind nor an extended chromosphere for the cool primary. Instead, the spectrum is like that of a single blue dwarf. The most likely reason for this contrast to all other Zeta Aur systems observed with IUE is the lower luminosity of the HR 6902 primary: a type-II 'bright giant' as opposed to the type I (or Ib-II in the case of 22 Vul) 'supergiants' in the other Zeta Aur systems.
Ahmad, Imad A.
Carbon and nitrogen abundances in the supergiants HD 93840 and zeta Per
NASA Technical Reports Server (NTRS)
The BN supergiant HD 93840 is shown to have the same temperature and surface gravity as the normal Bi Ib zeta Per. Differential abundance analysis of their C 4 and N 5 wind line profiles are found. The results are independent of the usual model atmosphere analyses and, therefore, a valuable check on them. Ratios for the C and N surface abundances in HD 93840 compared to Per of 1:10 and 4.6:1 are found respectively. By introducing a simple model for the compositions of both atmospheres the fraction of material in each atmosphere which has undergone CNO processing, more than 90 percent for HD 93840 and less than about 15 percent for zeta Per, is derived.
Massa, Derck; Altner, Bruce; Wynne, David; Lamers, H. J. G. L. M.
The Swift Supergiant Fast X-ray Transients Project: A review, new results and future perspectives
NASA Astrophysics Data System (ADS)
We present a review of the Supergiant Fast X-ray Transients (SFXT) Project, a systematic investigation of the properties of SFXTs with a strategy that combines Swift monitoring programs with outburst follow-up observations. This strategy has quickly tripled the available sets of broad-band data of SFXT outbursts, and gathered a wealth of out-of-outburst data, which have led us to a broad-band spectral characterization, an assessment of the fraction of the time these sources spend in each phase, and their duty cycle of inactivity. We present some new observational results obtained through our outburst follow-ups, as fitting examples of the exceptional capabilities of Swift in catching bright flares and monitor them panchromatically.
Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Vercellone, S.; Bocchino, F.; Burrows, D. N.; Kennea, J. A.; Krimm, H. A.; Gehrels, N.; Farinelli, R.; Ceccobello, C.
A semiempirical model for the red supergiant's wind in Zeta Aurigae systems
NASA Technical Reports Server (NTRS)
A semiempirical model for the wind in four Zeta Aur binary systems is developed, basing the analyses on the velocity function, nonthermal velocities, and upper limits to Ne/N(H) inferred from observations of the winds from the cool supergiants. The model assumes that the energy fluxes needed to drive the wind are supplied by Alfven waves, since the acoustic wave flux estimated from line broadening is too low. The damping scale length of the waves, is found to change from very small values near the star to larger values of the order of the local radius further out in the wind. The temperature structure and hydrogen ionization are derived for these models. Limits to the stellar magnetic field are found, as well as a necessary constraint for the existence of cool massive winds, suggesting that the dividing line in the H-R diagram is where this constraint is violated.
Kuin, N. P. M.; Ahmad, I. A.
HD16691: an extreme O-type supergiant with magnetically confined wind?
NASA Astrophysics Data System (ADS)
We propose to investigate the X-ray properties of HD16691, an O4 supergiant believed to be a transition object between O and Wolf-Rayet stars. Recent spectroscopic investigations by our team in the visible domain revealed a stellar wind affected by a large scale corotating structure, perhaps related to the interplay between the stellar magnetic field and the plasma outflow. This object constitutes therefore a valuable target for investigating the role of the potential magnetic confinement of the stellar wind. In addition, most of the O-type stars observed so far in X-rays belong to spectral types later than O5. An XMM-Newton study of HD16691 will therefore contribute to complete the picture of the X-ray properties of early-type stars.
De Becker, Michael
Triggered Star Formation and the Creation of the Supergiant H I Shell in IC 2574
NASA Astrophysics Data System (ADS)
Based on deep imaging from the Advanced Camera for Surveys aboard the Hubble Space Telescope (HST), we present new evidence that stellar feedback created a ~1 kpc supergiant H I shell (SGS) and triggered star formation (SF) around its rim in the M81 Group dwarf irregular galaxy IC 2574. Using photometry of the resolved stars from the HST images, we measure the star formation history of a region including the SGS, focusing on the past 500 Myr, and employ the unique properties of blue helium-burning stars to create a movie of SF in the SGS. We find two significant episodes of SF inside the SGS from 200-300 Myr and ~25 Myr ago. Comparing the timing of the SF events to the dynamic age of the SGS and the energetics from the H I and SF, we find compelling evidence that stellar feedback is responsible for creating the SGS and triggering secondary SF around its rim.
Weisz, Daniel R.; Skillman, Evan D.; Cannon, John M.; Walter, Fabian; Brinks, Elias; Ott, J�rgen; Dolphin, Andrew E.
Superorbital Periods in Supergiant High-Mass X-ray Binaries
NASA Astrophysics Data System (ADS)
Using data from the Swift Burst Alert Telescope (BAT) we discovered superorbital periods in four high-mass X-ray binaries accreting from the winds of supergiant primaries: 4U 1909+07 (= X 1908+075), IGR J16418-4532, IGR J16479-4514 and IGR J16493-4348. Together with a previously known superorbital period in 2S 0114+650, the systems show a surprising monotonic relationship between superorbital and orbital periods. We report on a continuing investigation of the superorbital modulation and searches for new superorbital periods including candidate superorbital modulation in IGR J16393-4643 (= AX J16390.4-4642) and 1E 1145.1-6141.
Corbet, Robin; Krimm, Hans A.
Identification of red supergiants in nearby galaxies with mid-IR photometry
NASA Astrophysics Data System (ADS)
Context. The role of episodic mass loss in massive-star evolution is one of the most important open questions of current stellar evolution theory. Episodic mass loss produces dust and therefore causes evolved massive stars to be very luminous in the mid-infrared and dim at optical wavelengths. Aims: We aim to increase the number of investigated luminous mid-IR sources to shed light on the late stages of these objects. To achieve this we employed mid-IR selection criteria to identity dusty evolved massive stars in two nearby galaxies. Methods: The method is based on mid-IR colors, using 3.6 ?m and 4.5 ?m photometry from archival Spitzer Space Telescope images of nearby galaxies and J-band photometry from 2MASS. We applied our criteria to two nearby star-forming dwarf irregular galaxies, Sextans A and IC 1613, selecting eight targets, which we followed-up with spectroscopy. Results: Our spectral classification and analysis yielded the discovery of two M-type supergiants in IC 1613, three K-type supergiants and one candidate F-type giant in Sextans A, and two foreground M giants. We show that the proposed criteria provide an independent way for identifying dusty evolved massive stars that can be extended to all nearby galaxies with available Spitzer/IRAC images at 3.6 ?m and 4.5 ?m. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio de El Roque de Los Muchachos of the Instituto de Astrof�sica de Canarias, on the island of La Palma, and the 2.5 m du Pont telescope in operation at Las Campanas Observatory, Chile.Spectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://184.108.40.206) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A75
Britavskiy, N. E.; Bonanos, A. Z.; Mehner, A.; Garc�a-�lvarez, D.; Prieto, J. L.; Morrell, N. I.
Quantitative Spectroscopy of Blue Supergiants in Metal-poor Dwarf Galaxy NGC�3109
NASA Astrophysics Data System (ADS)
We present a quantitative analysis of the low-resolution (~4.5 �) spectra of 12 late-B and early-A blue supergiants (BSGs) in the metal-poor dwarf galaxy NGC 3109. A modified method of analysis is presented which does not require use of the Balmer jump as an independent T eff indicator, as used in previous studies. We determine stellar effective temperatures, gravities, metallicities, reddening, and luminosities, and combine our sample with the early-B-type BSGs analyzed by Evans et al. to derive the distance to NGC 3109 using the flux-weighted gravity-luminosity relation (FGLR). Using primarily Fe-group elements, we find an average metallicity of [\\bar{Z}] = �0.67 � 0.13, and no evidence of a metallicity gradient in the galaxy. Our metallicities are higher than those found by Evans et al. based on the oxygen abundances of early-B supergiants ([\\bar{Z}] = �0.93 � 0.07), suggesting a low ?/Fe ratio for the galaxy. We adjust the position of NGC 3109 on the BSG-determined galaxy mass-metallicity relation accordingly and compare it to metallicity studies of H II regions in star-forming galaxies. We derive an FGLR distance modulus of 25.55 � 0.09 (1.27 Mpc) that compares well with Cepheid and tip of the red giant branch distances. The FGLR itself is consistent with those found in other galaxies, demonstrating the reliability of this method as a measure of extragalactic distances.
Hosek, Matthew W., Jr.; Kudritzki, Rolf-Peter; Bresolin, Fabio; Urbaneja, Miguel A.; Evans, Christopher J.; Pietrzy?ski, Grzegorz; Gieren, Wolfgang; Przybilla, Norbert; Carraro, Giovanni
THE RED SUPERGIANT PROGENITOR OF SUPERNOVA 2012aw (PTF12bvh) IN MESSIER 95
We report on the direct detection and characterization of the probable red supergiant (RSG) progenitor of the intermediate-luminosity Type II-Plateau (II-P) supernova (SN) 2012aw in the nearby (10.0 Mpc) spiral galaxy Messier 95 (M95; NGC 3351). We have identified the star in both Hubble Space Telescope images of the host galaxy, obtained 17-18 yr prior to the explosion, and near-infrared ground-based images, obtained 6-12 yr prior to the SN. The luminous supergiant showed evidence for substantial circumstellar dust, manifested as excess line-of-sight extinction. The effective total-to-selective ratio of extinction to the star was R'{sub V} Almost-Equal-To 4.35, which is significantly different from that of diffuse interstellar dust (i.e., R{sub V} = 3.1), and the total extinction to the star was therefore, on average, A{sub V} Almost-Equal-To 3.1 mag. We find that the observed spectral energy distribution for the progenitor star is consistent with an effective temperature of 3600 K (spectral type M3), and that the star therefore had a bolometric magnitude of -8.29. Through comparison with recent theoretical massive-star evolutionary tracks we can infer that the RSG progenitor had an initial mass 15 {approx}< M{sub ini}(M{sub Sun }) < 20. Interpolating by eye between the available tracks, we surmise that the star had initial mass {approx}17-18 M{sub Sun }. The circumstellar dust around the progenitor must have been destroyed in the explosion, as the visual extinction to the SN is found to be low (A{sub V} = 0.24 mag with R{sub V} = 3.1).
Van Dyk, Schuyler D. [Spitzer Science Center/Caltech, Mailcode 220-6, Pasadena, CA 91125 (United States); Cenko, S. Bradley; Filippenko, Alexei V., E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: email@example.com [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); and others
The behavior of the Mg II doublet features near 2800 A observed in F, A, and B supergiants
NASA Technical Reports Server (NTRS)
The Mg II doublet features near 2800 A were recently observed in F-, A-, and B-type supergiants with a balloon-borne ultraviolet stellar spectrometer. The stars observed are Alpha UMi (F8 Ib), Alpha Per (F5 Ib), Eta Leo (A0 Ib), and Rho Leo (B1 Ib). The Mg II doublet features in Alpha UMi and Alpha Per show emission superposed on photospheric absorption. In the spectrum of Eta Leo, the Mg II lines are in absorption and show shortward-shifted components attributable to mass loss. In the spectrum of Rho Leo, the Mg II lines are primarily a composite of the photospheric and interstellar absorption features. The general behavior of the Mg II lines for supergiants of spectral types M through B are also discussed.
Kondo, Y.; Morgan, T. H.; Modisette, J. L.
The Wind of the B[e] Supergiant Henize S22 Viewed through a Reflection Nebula in DEM L106
Narrowband HST WFPC2 images reveal a bow-shock-like halo around the H II region N30B toward the B[e] supergiant Hen S22 located within the larger DEM L106 nebula in the Large Magellanic Cloud. High-dispersion spectra of N30B show a narrow Halpha emission component from the ionized gas; the velocity variations indicate a gas flow of -5 to -10 km s-1 in
You-Hua Chu; C.-H. Rosie Chen; Charles Danforth; Bryan C. Dunne; Robert A. Gruendl; Ya�l Naz�; M. S. Oey
Crossing the Yellow Void: Spatially Resolved Spectroscopy of the Post-Red Supergiant IRC +10420 and Its Circumstellar Ejecta
IRC +10420 is one of the extreme hypergiant stars that define the empirical upper luminosity boundary in the H-R diagram. During their post-red supergiant evolution, these massive stars enter a temperature range (6000-9000 K) of increased dynamical instability, high mass loss, and increasing opacity, a semiforbidden region that de Jager and his collaborators have called the ``yellow void.'' We report
Roberta M. Humphreys; Kris Davidson; Nathan Smith
Distance and proper motion measurement of the Red Supergiant, S Persei, with VLBI H2O Maser astrometry
We have conducted Very Long Baseline Array phase-referencing monitoring of H2O masers around the red supergiant, S Persei, for six years. We have fitted maser motions to a simple expanding-shell model with a common annual parallax and stellar proper motion, and obtained the annual parallax as 0.413 � 0.017 mas and the stellar proper motion as (-0.49 � 0.23 mas
Y. Asaki; S. Deguchi; H. Imai; K. Hachisuka; M. Miyoshi; M. Honma
Effect of Cardiopulmonary Bypass Under Tepid Temperature on Inflammatory Reactions
Background. Cardiopulmonary bypass (CPB) causes inflammatory reactions and abnormal responses of vascular resistance. Theoretically, the difference in the blood temperature during CPB may influence the degree of CPB-induced inflammatory reactions.Methods. To elucidate the effect of the perfusate temperature during CPB, serum levels of inflammatory cytokines, neutrophil elastase, complements, and vasoactive substances were measured in 18 patients undergoing elective coronary artery
Toshihiro Ohata; Yoshiki Sawa; Keishi Kadoba; Takafumi Masai; Hajime Ichikawa; Hikaru Matsuda
INTEGRAL Long-Term Monitoring of the Supergiant Fast X-Ray Transient XTE J1739-302
NASA Technical Reports Server (NTRS)
Context. In the past few years, a new class of High Mass X-Ray Binaries (HMXRB) has been claimed to exist, the Supergiant Fast X-ray Transients (SFXT). These are X-ray binary systems with a compact companion orbiting a supergiant star which show very short and bright outbursts in a series of activity periods overimposed on longer quiescent periods. Only very recently the first attempts to model the behaviour of these sources have been published, some of them within the framework of accretion from clumpy stellar winds. Aims. Our goal is to analyze the properties of XTE J1739-302/IGR J17391-3021 within the context of the clumpy structure of the supergiant wind. Methods. We have used INTEGRAL and RXTE/PCA observations in order to obtain broad band (1 - 200 keV) spectra and light curves of XTE J1739-302 and investigate its X-ray spectrum and temporal variability. Results. We have found that XTE J1739-302 follows a much more complex behaviour than expected. Far from presenting a regular variability pattern, XTE J1739-302 shows periods of high, intermediate, and low flaring activity.
Blay, P.; Martinez-Nunez, S.; Negueruela, I.; Pottschmidt, K.; Smith, D. M.; Torrejon, J. M.; Reig, P.; Kretschmar, P.; Kreykenbohm, I.
X-Ray Emission from an Expanding Supergiant Shell in IC 2574
NASA Astrophysics Data System (ADS)
We present a multiwavelength study of a supergiant shell within the violent interstellar medium of the nearby dwarf galaxy IC 2574, which is a member of the M81 group of galaxies. Neutral hydrogen (H I) observations obtained with the Very Large Array (VLA) reveal a prominent expanding supergiant H I shell in the northeast quadrant of IC 2574 which is thought to be produced by the combined effects of stellar winds and supernova explosions. It measures roughly 1000�500 pc in size and is expanding at ~25 km s-1. The H I data suggest an age of ~1.4�106 yr; the energy input must have been of order (2.6+/-1)�1053 ergs. Massive star-forming regions, as traced by H? emission, are situated predominantly on the rim of this H I shell. This supports the view that the accumulated H I on the rim has reached densities that are high enough for secondary star formation to commence. VLA radio continuum observations at ?=6 cm show that these star-forming regions are the main sources of radio continuum emission in this galaxy. This emission is mainly thermal in origin. Soft X-ray emission from within the H I hole is detected by a pointed ROSAT PSPC observation. The emission is resolved, coinciding in size and orientation with the H I shell. These spatial properties suggest that the emission is generated by an X-ray-emitting plasma located within the H I shell, although a contribution from X-ray binaries cannot be completely ruled out. The X-ray luminosity within the 0.11-2.4 keV energy range is LX=(1.6+/-0.5)�1038 ergs s-1. The X-ray data are compatible with emission coming from a Raymond-Smith plasma at a temperature of about log(T[K])=6.8 and a density of ne~0.03 cm-3. The energy content of the coronal gas corresponds to (4+/-2)�1053 ergs, or broadly in agreement with the energy input derived on the basis of the H I observations.
Walter, Fabian; Kerp, J�rgen; Duric, Neb; Brinks, Elias; Klein, Uli
The characteristics of light variation of red supergiant (RSG) stars in the Small Magellanic Cloud (SMC) are analyzed based on the nearly 8-10 year data collected by the ASAS and MACHO projects. The 126 identified RSGs are classified into five categories accordingly: 20 with poor photometry, 55 with no reliable period, 6 with semi-regular variation, 15 with a long secondary period (LSP) and distinguishable short period, and 30 with only an LSP. For the semi-regular variables and the LSP variables with distinguishable short period, the K{sub S} -band period-luminosity (P-L) relation is analyzed and compared with that of the Galaxy, the Large Magellanic Cloud, and M33. It is found that the RSGs in these galaxies obey a similar P-L relation except for those in the Galaxy. In addition, the P-L relations in the infrared bands, namely, the 2MASS JHK{sub S} , Spitzer/IRAC, and Spitzer/MIPS 24 {mu}m bands, are derived with high reliability. The best P-L relation occurs in the Spitzer/IRAC [3.6] and [4.5] bands. Based on the comparison with the theoretical calculation of the P-L relation, the mode of pulsation of RSGs in the SMC is suggested to be the first-overtone radial mode.
Yang Ming; Jiang, B. W., E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)
Red supergiants in M31: extinction, metallicities and gas-to-dust ratio
NASA Astrophysics Data System (ADS)
We derived individual extinction values for selected red supergiant (RSGs) candidates in M31 with broadband photometry. Taking into account their position on the colour-magnitude diagram and using a probability method, the metallicity of each star was estimated. In the range 2-15 kpc the ratio [O/H] is nearly constant. The derived individual extinctions and pencil beams values from three different gas maps (Westerbork HI, VLA HI and IRAM CO (1?0)-line survey) were used to obtain gas-to-dust ratio in M31. For the 9 most luminous stars both the ratios N(HI)/2 EB-V and N(HI+H2)/2EB-V are not very different from those in the Milky Way. Significant fractions outside the expected range of Galactic atomic gas-to-dust ratio are obtained for ~1/3 of the sample using Westerbork and for ~1/2 of the sample using VLA maps. The ratios are overestimated for objects located high above the midplane of M31 and underestimated - due to resolution effects, - for several RSGs coinciding with small HI clouds.
Nedialkov, Petko; Veltchev, Todor
Spectroscopic study of the O-type runaway supergiant HD 195592
NASA Astrophysics Data System (ADS)
The scope of this paper is to perform a detailed spectroscopic study of the northern O-type supergiant HD 195592. We use a large sample of high quality spectra in order to investigate its multiplicity, and to probe the line profile variability. Our analysis reveals a clear spectroscopic binary signature in the profile of the He I? 6678 line, pointing to a probable O + B system. We report on low amplitude radial velocity variations in every strong absorption line in the blue spectrum of HD 195592. These variations are ruled by two time-scales, respectively, of 5.063 and about 20 days. The former is firmly established, whilst the latter is poorly constrained. We report also on a very significant line profile variability of the H ? line, with time scales strongly related to those of the radial velocities. Our results provide significant evidence that HD 195592 is a binary system, with a period that might be the variability time-scale of about 5 days. The second time scale may be the signature of an additional star moving along a wider orbit provided its mass is low enough, even though direct evidence for the presence of a third star is still lacking. Alternatively, the second time-scale may be the signature of a variability intrinsic to the stellar wind of the primary, potentially related to the stellar rotation.
De Becker, M.; Linder, N.; Rauw, G.
Quantitative Spectroscopic J-band study of Red Supergiants in Perseus OB-1
NASA Astrophysics Data System (ADS)
We demonstrate how the metallicities of red supergiant (RSG) stars can be measured from quantitative spectroscopy down to resolutions of ?3000 in the J-band. We have obtained high resolution spectra on a sample of the RSG population of h and ? Persei, a double cluster in the solar neighborhood. We show that careful application of the MARCS model atmospheres returns measurements of Z consistent with solar metallicity. Using two grids of synthetic spectra�one in pure LTE and one with non-LTE (NLTE) calculations for the most important diagnostic lines�we measure Z = +0.04 � 0.10 (LTE) and Z = �0.04 � 0.08 (NLTE) for the sample of eleven RSGs in the cluster. We degrade the spectral resolution of our observations and find that those values remain consistent down to resolutions of less than ?/?? of 3000. Using measurements of effective temperatures we compare our results with stellar evolution theory and find good agreement. We construct a synthetic cluster spectrum and find that analyzing this composite spectrum with single-star RSG models returns an accurate metallicity. We conclude that the RSGs make ideal targets in the near infrared for measuring the metallicities of star forming galaxies out to 7-10 Mpc and up to 10 times farther by observing the integrated light of unresolved super star clusters. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.
Gazak, J. Zachary; Davies, Ben; Kudritzki, Rolf; Bergemann, Maria; Plez, Bertrand
X-Ray Observation of the Shocked Red Supergiant Wind of Cassiopeia A
NASA Astrophysics Data System (ADS)
Cas A is a Galactic supernova remnant whose supernova explosion is observed to be of Type IIb from spectroscopy of its light echo. Having its SN type known, observational constraints on the mass-loss history of Cas A's progenitor can provide crucial information on the final fate of massive stars. In this paper, we study X-ray characteristics of the shocked ambient gas in Cas A using the 1 Ms observation carried out with the Chandra X-Ray Observatory and try to constrain the mass-loss history of the progenitor star. We identify thermal emission from the shocked ambient gas along the outer boundary of the remnant. Comparison of measured radial variations of spectroscopic parameters of the shocked ambient gas to the self-similar solutions of Chevalier show that Cas A is expanding into a circumstellar wind rather than into a uniform medium. We estimate a wind density n H ~ 0.9 � 0.3 cm-3 at the current outer radius of the remnant (~3 pc), which we interpret as a dense slow wind from a red supergiant (RSG) star. Our results suggest that the progenitor star of Cas A had an initial mass around 16 M ?, and its mass before the explosion was about 5 M ?, with uncertainties of several tens of percent. Furthermore, the results suggest that, among the mass lost from the progenitor star (~11 M ?), a significant amount (more than 6 M ?) could have been via its RSG wind.
Lee, Jae-Joon; Park, Sangwook; Hughes, John P.; Slane, Patrick O.
Ultraviolet and optical spectroscopy of a B supergiant star in M 31
NASA Astrophysics Data System (ADS)
We present and discuss the UV spectrum of the supergiant star in NGC206-277 in M 31, obtained with the Faint Object Spectrograph (FOS) on Hubble Space Telescope (HST). An optical blue spectrum taken at Kitt Peak National Observatory (KPNO) is also shown. From the optical and UV line spectra we classify the star B1.5Ia. We fit the continuum far-UV flux distribution, deriving Teff = 20,000 K, and with this temperature we find log g = 2.5 by comparing the Hgamma line and He I lines with predictions from Non-Local Thermodynamic Equilibrium (NLTE) models. We analyze the stellar UV wind line profiles with the SEI method and derive a terminal velocity of upsiloninfinity approximately equal to 700 km/s. We fit the Halpha emission line obtained at the WHT with a newly developed (by H.J.G.L.M.L.) code similar to the SEI method for UV lines, and derive dm/dt = 1.3 +/- 0.5 10-6 solar mass/yr. We find that the P Cygni profiles of the M 31 star have slightly weaker and narrower absorptions, and no emission component. We correct our previously published mass-loss estimate for an O star (NGC206-231) in the same association. The correct value is dm/dt approximately equals 10-6 solar mass/yr, assuming solar abundances.
Bianchi, Luciana; Lamers, Henry J. G. L. M.; Hutchings, J. B.; Massey, Philip; Kudritzki, Rolf; Herrero, Artemio; Lennon, Danny J.
Wolf-Rayet, Yellow and Red Supergiant in the single massive stars perspective
NASA Astrophysics Data System (ADS)
Rotation and mass loss are the key ingredients determining the fate of single massive stars. In recent years, a large effort has been made to compute whole grids of stellar models at different metallicities, including or not the effects of rotation, with the Geneva evolution code. In this talk, I will focus on the evolved stages of massive star evolution (red and yellow supergiants, Wolf-Rayet stars), in the framework of these new grids of models. I will highlight the effects of rotation and mass loss on the post-main sequence evolution of massive stars at solar and lower metallicity. In particular, I will discuss their impact on the maximum mass for a star to end its life as a RSG (leading to a type IIP supernova), on the possibility for a star to finish as a YSG, and on the initial mass ranges leading to various WR star subtypes. I will then compare the results predicted by our code with observed populations of evolved massive stars, bringing constraints on our computations, as well as some indications on the binary star fraction needed to reproduce them.
Georgy, Cyril; Hirschi, R.; Ekstrom, S.; Meynet, G.
Spectral Types of Red Supergiants in NGC 6822 and the Wolf-Lundmark-Melotte Galaxy
NASA Astrophysics Data System (ADS)
We present moderate-resolution spectroscopic observations of red supergiants (RSGs) in the low-metallicity Local Group galaxies NGC 6822 (Z = 0.4 Z ?) and Wolf-Lundmark-Melotte (WLM; Z = 0.1 Z ?). By combining these observations with reduction techniques for multislit data reduction and flux calibration, we are able to analyze spectroscopic data of 16 RSGs in NGC 6822 and spectrophotometric data of 11 RSGs in WLM. Using these observations, we determine spectral types for these massive stars, comparing them to Milky Way and Magellanic Cloud RSGs and thus extending observational evidence of the abundance-dependent shift of RSG spectral types to lower metallicities. In addition, we have uncovered two RSGs with unusually late spectral types (J000158.14-152332.2 in WLM, with a spectral type of M3 I, and J194453.46-144552.6 in NGC 6822, with a spectral type of M4.5 I) and a third RSG (J194449.96-144333.5 in NGC 6822) whose spectral type has varied from an M2.5 in 1997 to a K5 in 2008. All three of these stars could potentially be members of a recently discovered class of extreme RSG variables. This paper is based on data gathered with the 6.5 m Magellan telescopes located at Las Campanas, Chile.
Levesque, Emily M.; Massey, Philip
Cumulative luminosity distributions of supergiant fast X-ray transients in hard X-rays
NASA Astrophysics Data System (ADS)
We have analysed in a systematic way about nine years of INTEGRAL data (17-100 keV) focusing on supergiant fast X-ray transients (SFXTs) and three classical high-mass X-ray binaries (HMXBs). Our approach has been twofold: image-based analysis, sampled over a �ks time frame to investigate the long-term properties of the sources and light-curve-based analysis, sampled over a 100 s time frame to seize the fast variability of each source during its � ks activity. We find that while the prototypical SFXTs (IGR J17544-2619, XTE J1739-302 and SAX J1818.6-1703) are among the sources with the lowest � ks-based duty cycle (<1 per cent activity over nine years of data), when studied at the 100 s level, they are the ones with the highest detection percentage, meaning that, when active, they tend to have many bright short-term flares with respect to the other SFXTs. To investigate in a coherent and self-consistent way all the available results within a physical scenario, we have extracted cumulative luminosity distributions for all the sources of the sample. The characterization of such distributions in hard X-rays, presented for the first time in this work for the SFXTs, shows that a power-law model is a plausible representation for SFXTs, while it can only reproduce the very high luminosity tail of the classical HMXBs, and even then, with a significantly steeper power-law slope with respect to SFXTs. The physical implications of these results within the frame of accretion in wind-fed systems are discussed.
Paizis, A.; Sidoli, L.
From previous samples of red supergiants (RSGs) by various groups, 191 objects are assembled to compose a large sample of RSG candidates in LMC. For 189 of them, the identity as an RSG is verified by their brightness and color indexes in several near- and mid-infrared bands related to the Two Micron All Sky Survey (2MASS) JHK{sub S} bands and the Spitzer/IRAC and Spitzer/MIPS bands. From the visual time-series photometric observations by the ASAS and MACHO projects which cover nearly 8-10 years, the period and amplitude of light variation are analyzed carefully using both the phase dispersion minimization and Period04 methods. According to the properties of light variation, these objects are classified into five categories: (1) 20 objects are saturated in photometry or located in crowded stellar field with poor photometric results, (2) 35 objects with too complex variation to have any certain period, (3) 23 objects with irregular variation, (4) 16 objects with semi-regular variation, and (5) 95 objects with long secondary period (LSP) among which 31 have distinguishable short period and 51 have a long period shorter than 3000 days that can be determined with reasonable accuracy. For the semi-regular variables and the LSP variables with distinguishable short periods, the period-luminosity (P-L) relation is analyzed in the visual, near-infrared, and mid-infrared bands. It is found that the P-L relation is tight in the infrared bands such as the 2MASS JHK{sub S} bands and the Spitzer/IRAC bands, in particular in the Spitzer/IRAC [3.6] and [4.5] bands; meanwhile, the P-L relation is relatively sparse in the V band which may be caused by inhomogeneous interstellar extinction. The results are compared with others' P-L relationships for RSGs and the P-L sequences of red giants in LMC.
Yang Ming; Jiang, B. W., E-mail: firstname.lastname@example.com, E-mail: email@example.com [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)
Long-term spectroscopic monitoring of BA-type supergiants. I. Halpha_ line-profile variability.
NASA Astrophysics Data System (ADS)
We have obtained time series of spectra in the wavelength range 4000-6800 A over several months with high S/N and high resolution in wavelength (?/{DELTA}?=~20000) and time ({DELTA}t=~1d) of the late-type B and early-type A supergiants HD91619 (B7Ia), ?Ori (B8Ia), HD96919 (B9Ia), HD92207 (A0Ia), HD100262 (A2Ia) and ?Cyg (A2Ia). Halpha_ is found to show broad emission extended to about +/-1200km/s for all objects except ?Cyg. Due to the lack of strong line-emission in Halpha_ the electron-scattered photons are expected to originate in deep atmospheric layers. In all of the objects the Halpha_-line profiles are found to be highly variable on different time scales reaching from days to months. Patterns of variation in Halpha_ are found to be quite symmetric about the systemic velocity and are mainly due to variable blue and red-shifted emission superimposed on almost constant photospheric and/or wind profiles. These V/R variations are interpreted in terms of axial symmetry of the envelopes of these objects. Time-series analyses of the variations reveal Halpha_ time scales up to a factor of 6 longer than expected radial fundamental pulsation periods but consistent with rotational periods. Therefore, rotational modulation as a possible source of variability is concluded. Corotating weak magnetic surface structures are suggested as the source for a rotationally modulated lower wind region. Suddenly appearing deep and highly blue-shifted absorptions in Halpha_ are ascribed to instabilities of the ionization structure of the wind. Outwards propagating discrete absorption components have been observed only once in HD92207.
Kaufer, A.; Stahl, O.; Wolf, B.; Gaeng, T.; Gummersbach, C. A.; Kovacs, J.; Mandel, H.; Szeifert, T.
Long-term spectroscopic monitoring of BA-type supergiants. III. Variability of photospheric lines.
NASA Astrophysics Data System (ADS)
We obtained time series of spectra with high S/N and high resolution in wavelength and time of early-type A and late-type B supergiants (cf. Kaufer et al. 1996A&A...305..887K, Paper I, and Kaufer et al. 1996A&A...314..599K, Paper II for the analysis of the variability of the stellar envelopes). In this work we inspect the time variations of the numerous photospheric line profiles in the optical spectrum. We find complex cyclical variations of the radial velocities with a typical velocity dispersion of ?=~3km/s. The corresponding equivalent-width variations are less than 1% of their mean if we assume a common modulation mechanism for both radial velocities and equivalent width. We do not find any depth dependence of the velocity fields in the metallic lines. For ?Cyg the Balmer lines show an increase of the radial velocity from H27 to H8 by 3km/s, which is identified with the onset of the radially accelerating velocity field of the stellar wind. The Cleaned periodograms of the radial-velocity curves show the simultaneous excitation of multiple pulsation modes with periods longer and shorter than the estimated radial fundamental periods of the objects, which might indicate the excitation of non-radial and radial overtones, respectively. The analysis of the line-profile variations (LPV) of the photospheric line spectrum reveals prograde travelling features in the dynamical spectra. The travelling times of these features are in contradiction to the possible rotation periods of these extended, slowly rotating objects. Therefore, we suggest that these features should be identified with non-radial pulsation modes, possibly g-modes, of low order (l=|m|<~5).
Kaufer, A.; Stahl, O.; Wolf, B.; Fullerton, A. W.; Gaeng, T.; Gummersbach, C. A.; Jankovics, I.; Kovacs, J.; Mandel, H.; Peitz, J.; Rivinius, T.; Szeifert, T.
A New Distance to M33 Using Blue Supergiants and the FGLR Method
NASA Astrophysics Data System (ADS)
The quantitative spectral analysis of medium resolution optical spectra of A and B supergiants obtained with DEIMOS and ESI at the Keck Telescopes is used to determine a distance modulus of 24.93 � 0.11 mag (968 � 50 kpc) for the Triangulum Galaxy M33. The analysis yields stellar effective temperatures, gravities, interstellar reddening, and extinction, the combination of which provides a distance estimate via the flux-weighted gravity-luminosity relationship (FGLR). This result is based on an FGLR calibration that is continually being polished. An average reddening of langE(B - V)rang ~ 0.08 mag is found, with a large variation ranging from 0.01 to 0.16 mag, however, demonstrating the importance of accurate individual reddening measurements for stellar distance indicators in galaxies with evident signatures of interstellar absorption. The large-distance modulus found is in good agreement with recent work on eclipsing binaries, planetary nebulae, long-period variables, RR Lyrae stars, and also with Hubble Space Telescope (HST) observations of Cepheids, if reasonable reddening assumptions are made for the Cepheids. Since distances based on the tip of the red giant branch (TRGB) method found in the literature give conflicting results, we have used HST Advanced Camera for Surveys V- and I-band images of outer regions of M33 to determine a TRGB distance of 24.84 � 0.10 mag, in basic agreement with the FGLR result. We have also determined stellar metallicities and discussed the metallicity gradient in the disk of M33. We find metallicity of Z sun at the center and 0.3 Z sun in the outskirts at a distance of one isophotal radius. The average logarithmic metallicity gradient is -0.07 � 0.01 dex kpc-1. However, there is a large scatter around this average value, very similar to what has been found for the H II regions in M33.
U, Vivian; Urbaneja, Miguel A.; Kudritzki, Rolf-Peter; Jacobs, Bradley A.; Bresolin, Fabio; Przybilla, Norbert
A FEROS spectroscopic study of the extreme O supergiant He 3-759
NASA Astrophysics Data System (ADS)
We present a study of the extreme O-type supergiant He 3-759 using new high-resolution FEROS data, revealing that it is a near spectroscopic twin of HD 151804 (O8 Iaf). We investigate the extinction towards He 3-759 using a variety of methods, revealing AV � 4.7^m. If we assume He 3-759 has an identical absolute K-band magnitude to HD 151804 we find that it lies in the Sagittarius-Carina spiral arm at a distance of 6.5 kpc. We derive the physical and wind properties for He 3-759, revealing Tast = 30.5 kK, log L/L? = 5.9 and dot{M} = 10-5.17 M? yr-1 for a clumped wind whose terminal velocity is estimated at 1000 km s-1. The atmosphere of He 3-759 is enriched in helium (X_He = 49%) and nitrogen (XN = 0.3%). A reanalysis of HD 151804 and HD 152408 (WN9ha) reveals similar parameters except that the WN9ha star possesses a stronger wind and reduced surface hydrogen content. HD 151804 and HD 152408 lie within the Sco OB1 association, with initial masses of 60 M? and ages 2.7 Myr, consistent with NGC 6231 cluster members using standard Geneva isochrones. Improved agreement with observed surface abundances are obtained for similar initial masses with more recent Geneva group predictions from which higher ages of 3.75 Myr are obtained. No young, massive star cluster is known to be associated with He 3-759. Based on observations made with ESO telescopes at the La Silla observatory under program ID 082-D.0136.
Crowther, P. A.; Evans, C. J.
The red supergiants and Wolf-Rayet stars of NGC 604
NASA Astrophysics Data System (ADS)
We study the post-main-sequence stars in NGC 604, the most luminous H II region in M33. A number of Wolf-Rayet (WR) stars and one red supergiant (RSG) were discovered earlier. Based on the broad-band photometry of the region, we present evidence that is consistent with the presence of this RSG and with three more RSG candidates. Using spectral energy distribution (SED) fitting based on Hubble Space Telescope UVIJHK photometry, we estimate the ages of the WR stars and RSGs and find that the two populations are from distinct formation episodes with ages of 3.2 � 1.0 and 12.4 � 2.1 Myr, respectively. The RSGs have greater extinctions towards their line of sight than the WR stars which is consistent with the production of a large amount of dust by the RSGs. Using the WR and RSG populations and similar SED fits to the most massive O stars, we estimate that the total stellar mass is (3.8 � 0.6) � 105 M?. We find a large discrepancy between the expected H? flux from such a massive cluster and the one observed. This suggests that 49+16-19 per cent of the ionizing photons produced by massive stars in NGC 604 are leaking from this H II region. We also suggest that the implications of an old RSG population mean that if NGC 604 were more distant and only observed in the infrared, it would be difficult to study the youngest burst of star formation due to the contamination of RSGs.
Eldridge, John J.; Rela�o, M�nica
Exploring jet-launching conditions for supergiant fast X-ray transients
NASA Astrophysics Data System (ADS)
Context. In the magneto-centrifugal mechanism for jet formation, accreting neutron stars are assumed to produce relativistic jets only if their surface magnetic field is weak enough (B ~ 108 G). However, the most common manifestation of neutron stars are pulsars, whose magnetic field distribution peaks at B ~ 1012 G. If the neutron star magnetic field has at least this strength at birth, it must decay considerably before jets can be launched in binary systems. Aims: We study the magnetic field evolution of a neutron star that accretes matter from the wind of a high-mass stellar companion so that we can constrain the accretion rate and the impurities in the crust, which are necessary conditions for jet formation. Methods: We solved the induction equation for the diffusion and convection of the neutron star magnetic field confined to the crust, assuming spherical accretion in a simpliflied one-dimensional treatment. We incorporated state-of-the-art microphysics, including consistent thermal evolution profiles, and assumed two different neutron star cooling scenarios based on the superfluidity conditions at the core. Results: We find that in this scenario, magnetic field decay at long timescales is governed mainly by the accretion rate, while the impurity content and thermal evolution of the neutron star play a secondary role. For accretion rates ? ? 10-10 M? yr-1, surface magnetic fields can decay up to four orders of magnitude in ~107 yr, which is the timescale imposed by the evolution of the high-mass stellar companion in these systems. Based on these results, we discuss the possibility of transient jet-launching in strong wind-accreting high-mass binary systems like supergiant fast X-ray transients.
Garc�a, Federico; Aguilera, Deborah N.; Romero, Gustavo E.
The Wind of the B[e] Supergiant Hen S22 Viewed through a Reflection Nebula in DEM L 106
Narrow-band HST WFPC2 images reveal a bow-shock-like halo around the HII\\u000aregion N30B toward the B[e] supergiant Hen S22 located within the larger DEM L\\u000a106 nebula in the Large Magellanic Cloud. High-dispersion spectra of N30B show\\u000aa narrow H-alpha emission component from the ionized gas; the velocity\\u000avariations indicate a gas flow of -5 to -10 km\\/s in the
Y.-H. Chu; C.-H. R. Chen; C. Danforth; B. C. Dunne; R. A. Gruendl; Y. Naze; M. S. Oey
The period - K-band luminosity relation for pulsating variable red supergiants in the Galaxy and in M 33
NASA Astrophysics Data System (ADS)
The paper reports the detection of a double-mode period - IR-luminosity relation for pulsating red supergiants (SRC-type variables) in the Galaxy. Distance moduli of LMC and of M 33 are estimated on the basis of the adopted distance modulus of 11.4 for the Per OB1 stellar association. The ratio of the first overtone pulsation period to that of the main tone is found to be the same both in the Galaxy and in M 33 (0.70 +/- 0.04).
Dambis, A. K.
Swift/XRT Monitoring of the Candidate Supergiant Fast X-ray Transient IGR J16418-4532
NASA Technical Reports Server (NTRS)
We report on the Swift monitoring of the candidate supergiant fast X-ray transient (SFXT) IGR J16418.4532, for which both orbital and spin periods are known (approx. 3.7d and approx. 1250 s, respectively). Our observations, for a total of approx. 43 ks, span over three orbital periods and represent the most intense and complete sampling of the light curve of this source with a sensitive X-ray instrument. With this unique set of observations we can address the nature of this transient. By applying the clumpy wind model for blue supergiants to the observed X-ray light curve, and assuming a circular orbit, the X-ray emission from this source can be explained in terms of the accretion from a spherically symmetric clumpy wind, composed of clumps with different masses, ranging from 5 X 10(exp 16) g to 10(exp 21) g. Our data suggest, based on the X-ray behaviour, that this is an intermediate SFXT
Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Evans, P. A.; Vercellone, S.; Kennea, J. A.; Burrows, D. N.; Gehrels, N.
A Five-year Spectroscopic and Photometric Campaign on the Prototypical ? Cygni Variable and A-type Supergiant Star Deneb
NASA Astrophysics Data System (ADS)
Deneb is often considered the prototypical A-type supergiant and is one of the visually most luminous stars in the Galaxy. A-type supergiants are potential extragalactic distance indicators, but the variability of these stars needs to be better characterized before this technique can be considered reliable. We analyzed 339 high-resolution echelle spectra of Deneb obtained over the five-year span of 1997 through 2001 as well as 370 Str�mgren photometric measurements obtained during the same time frame. Our spectroscopic analysis included dynamical spectra of the H? profile, H? equivalent widths, and radial velocities measured from Si II ?? 6347, 6371. Time-series analysis reveals no obvious cyclic behavior that proceeds through multiple observing seasons, although we found a suspected 40 day period in two, non-consecutive observing seasons. Some correlations are found between photometric and radial velocity data sets and suggest radial pulsations at two epochs. No correlation is found between the variability of the H? profiles and that of the radial velocities or the photometry. Lucy found evidence that Deneb was a long-period single-lined spectroscopic binary star, but our data set shows no evidence for radial velocity variations caused by a binary companion.
Richardson, N. D.; Morrison, N. D.; Kryukova, E. E.; Adelman, S. J.
Visual, Near-IR, and TiO Spectrophotometry of Pulsating Giant and Supergiant M-Type Variable Stars
NASA Astrophysics Data System (ADS)
Pulsating M-type giant and supergiant stars radiate mainly in the near to intermediate IR (1000-2000 nm). Since most prior long-term photometric observations have been done visually or with UBVRI filters, an on-going program was established to monitor selected stars using both wide-band visual (550 nm) and Wing (719 nm, 754 nm, and 1040 nm) intermediate band filters. Outer atmopsheric titanium-oxide (TiO) strenghts are calculated and compared with generated visual light curves to study correlations of stellar pulsa- tions with molecular formation. IR color temperatures are computed and are used in combination with measured bolome- tric magnitudes to estimate radii changes throughout pulsa- tional cycles. These results should provide information relevant for studies of internal structures, atmopsheres, and evolution of red giant and supergiant stars. Some stars currently being observed include Mira, Aldebaran, Alpha Her, Betelgeuse, V CVn, R Leo, and CE Tau. Additionally, a calibration of the Wing 3-color spectro- photometry sytem is in progress to correlate TiO strengths with known spectral types and near-IR color temperatures for the benefit of the community. Observations measuring spectral sub-type changes via cyclic pulsational variations in TiO-indices and near-IR color temperature changes will be more accurate once the calibration is completed. This work was in part supported by NSF grant AST-9315365, which we gratefully acknowledge.
Wasatonic, R. P.; Guinan, E. F.
The Reddening of Red Supergiants: When Smoke Gets in Your Eyes
NASA Astrophysics Data System (ADS)
Deriving the physical properties of red supergiants (RSGs) depends on accurate corrections for reddening by dust. We use our recent modeling of the optical spectra of RSGs to address this topic. First, we find that previous broadband studies have underestimated the correction for extinction in the visible, and hence the luminosities (if derived from V); the shift in the effective wavelengths of the standard B and V bandpasses necessitates using an effective value of the ratio R'V=4.2 to correct broadband photometry of RSGs if RV=3.1 for early-type stars viewed through the same dust, where we have assumed the standard reddening law of Cardelli and coauthors. Use of the Fitzpatrick reddening law would lead to R'V=3.8, as well as slightly lower values of extinction derived from spectrophotometry, but results in slightly poorer fits. Second, we find that a significant fraction of RSGs in Galactic OB associations and clusters show up to several magnitudes of excess visual extinction compared to OB stars in the same regions; we argue that this is likely due to circumstellar dust around the RSGs. We also show that the RSG dust production rate (as indicated by the 12 ?m excess) is well correlated with bolometric luminosity, contrary to what has been found by earlier studies. The stars with the highest amount of extra visual extinction also show significant near-UV (NUV) excesses compared to the stellar models reddened by the standard reddening law. This NUV excess is likely due to scattering of the star's light by the dust and/or a larger average grain size than that typical of grains found in the diffuse interstellar medium. Similar excesses have been attributed to circumstellar dust around R Coronae Borealis stars. Finally, we estimate that the RSGs contribute dust grains at the rate of 3�10-8Msolar yr-1 kpc-2 in the solar neighborhood, comparable to what we estimate for late-type WCs, 1�10-7Msolar yr-1 kpc-2. In the solar neighborhood this represents only a few percent of the dust production (which is dominated by low-mass AGBs), but we note that in low-metallicity starbursts, dust production by RSGs would likely dominate over other sources.
Massey, Philip; Plez, Bertrand; Levesque, Emily M.; Olsen, K. A. G.; Clayton, Geoffrey C.; Josselin, Eric
Spectral variability of luminous early type stars . II. Supergiant alpha Camelopardalis
NASA Astrophysics Data System (ADS)
Time-series of H? spectra with relatively high resolution in wavelength (R = lambda /delta lambda of 15 000 to 22 000) and time (Delta t = 1d) of the late-type O supergiant alpha Cam are analysed in terms of line-profile variability (lpv). The spectra cover an interval of one year, from February 1998 to February 1999. The analysis provides clear evidence of a continuous deep-seated wind activity traced by variations in the H? emission and He I lambda 6678.15 absorption lines. The observations indicate that the wind is not smooth but perturbed, starting from its base up to velocities of ~ 500 km s-1. The character of the medium-term (days) variations found in H? changes between epochs, and appears to require an explanation involving different kinds of wind perturbations. In particular, we found that in June and July 1998 as well as in February 1999 the lpv of H? was dominated by low-amplitude (<=+/-10%) variations in line flux which usually occupy the central part of the profile symmetrically with respect to the line center while in December 1998 and January 1999 the variations were organised in two wave-like modulations that run from ``red'' to ``blue" and back to ``red" within the profile (between +/-300 km s-1), being most of the time in antiphase. The timescale of variation, revealed via Fourier analysis, is respectively ~ 7 and ~ 10 days. Significant variations in emission equivalent width (up to 35%), closely linked to those in the line profile, are also noted. Short-term (3 to 4 days), low-amplitude (<=22%) variation in mass loss rate which recurs on a timescale of ~ 7 days giving rise to the formation of outward accelerating consecutive shells or/and blobs was suggested to explain the lpv of H? in June-July 1998 and in February 1999. Whereas the variability pattern observed in December-January 1999 seems to be qualitatively consistent with a model involving two rotationally-modulated wind perturbations, one of enhanced density and another of reduced density with respect to the mean, which are not symmetric about the center of the star. Strange-mode oscillations or radial fundamental pulsation are discussed as possible mechanisms generating the established wind variability.
Markova, N.
Wind Variability of B Supergiants. No. 2; The Two-component Stellar Wind of gamma Arae
NASA Technical Reports Server (NTRS)
The stellar wind of the rapidly rotating early-B supergiant, gamma Ara, is studied using time series, high-resolution IUE spectroscopy secured over approx. 6 days in 1993 March. Results are presented based on an analysis of several line species, including N(N), C(IV), Si(IV), Si(III), C(II), and Al(III). The wind of this star is grossly structured, with evidence for latitude-dependent mass loss which reflects the role of rapid rotation. Independent, co-existing time variable features are identified at low-velocity (redward of approx. -750 km/s) and at higher-speeds extending to approx. -1500 km/s. The interface between these structures is 'defined' by the appearance of a discrete absorption component which is extremely sharp (in velocity space). The central velocity of this 'Super DAC' changes only gradually, over several days, between approx. -400 and -750 km/s in most of the ions. However, its location is shifted redward by almost 400 km/s in Al(III) and C(II), indicating that the physical structure giving rise to this feature has a substantial velocity and ionization jump. Constraints on the relative ionization properties of the wind structures are discussed, together with results based on SEI line-profile-fitting methods. The overall wind activity in gamma Ara exhibits a clear ion dependence, such that low-speed features are promoted in low-ionization species, including Al(III), C(II), and Si(III). We also highlight that - in contrast to most OB stars - there are substantial differences in the epoch-to-epoch time-averaged wind profiles of gamma Ara. We interpret the results in terms of a two-component wind model for gamma Ara, with an equatorially compressed low ionization region, and a high speed, higher-ionization polar outflow. This picture is discussed in the context of the predicted bi-stability mechanism for line-driven winds in rapidly rotating early-B type stars, and the formation of compressed wind regions in rapidly rotating hot stars. The apparent absence of a substantial shift in the wind ionization mixture of gamma Ara, and the normal nature of its photospheric spectrum, suggests wind-compression as the likely dominant cause for the observed equatorial density enhancements.
Prinja, R. K.; Massa, D.; Fullerton, A. W.; Howarth, I. D.; Pontefract, M.
A study on the nature of the peculiar supergiant HD 101584.
NASA Astrophysics Data System (ADS)
We present a study of low- and high-resolution ultraviolet, high-resolution optical CAT/CES spectra and ultraviolet, optical and infrared photometry of the peculiar supergiant HD 101584. From the photometry we learn that the ultraviolet and optical energy distribution cannot be fitted in a consistent way and we need a model in which the UV and optical energy distribution are formed by different gas. The Geneva photometry is best fitted to a B9II Kurucz model, T_eff_=12000+/-1000K and logg=3.0+/-1.0, with an extinction of E(B-V)=0.49+/-0.05. The observed spectral features in the spectrum of HD 101584 are classified in eight different categories based on the velocity, shape of profile and the identification. The high-excitation HeI (?=20.87eV), NII (?=18.40eV), CII (?=14.39eV) and NI (?=10.29eV) optical absorption lines are formed in the photosphere of a late B-star (e.g. B8-9I-II). These absorption lines show radial velocity variations which are attributed to binary motion, with the secondary being a white dwarf or a low-mass main sequence object. The low-excitation P-Cygni lines in the optical and UV are formed in the wind. The number density of absorption lines in the UV is so large that the wind spectrum acts as an iron curtain in front of the B-star. The terminal velocity of the wind of vinfinity_=100+/-30km/s is consistent with the star being a low-mass post-AGB star and the low effective gravity is attributed to the presence of a nearby, unseen, secondary. We estimate a mass-loss rate of M?=~10^-8^Msun_/yr. Narrow absorption and emission lines are observed which are formed in a circumsystem disk with a typical radius of 10^2^R_*_.
Bakker, E. J.; Lamers, H. J. G. L. M.; Waters, L. B. F. M.; Waelkens, C.; Trams, N. R.; Van Winckel, H.
Red Supergiants, Luminous Blue Variables and Wolf-Rayet stars: the single massive star perspective
NASA Astrophysics Data System (ADS)
We discuss, in the context of the single star scenario, the nature of the progenitors of Red Supergiants (RSG), of Luminous Blue Variables (LBV) and of Wolf-Rayet (WR) stars. These three different populations correspond to evolved phases of Main-Sequence (MS) OB stars. Axial rotation and mass loss have a great influence on massive star evolution in general and more specifically on the durations of these different phases. Moderate rotation and mass loss, during the MS phase, favor the evolution towards the RSG stage. Fast rotation and strong mass loss during the MS phase, in contrast, prevent the star from becoming a RSG and allow the star to pass directly from the OB star phase into the WR phase. Mass loss during the RSG stage may make the star evolve back in the blue part of the HR diagram. We argue that such an evolution may be more common than presently accounted for in stellar models. This might be the reason for the lack of type IIP SNe with RSG progenitors having initial masses between 18 and 30 M_?. The LBVs do appear as a possible transition phase between O and WR stars or between WNL and WNE stars. Fast rotation and/or strong mass loss during the Main-Sequence phase prevent the formation of LBV stars. The mechanisms driving the very strong ejections shown by LBV stars are still unknown. We present some arguments showing that axial rotation together with the proximity of the Eddington limit may play a role in driving the shell ejections. Rotation and mass loss favor the formation of Wolf-Rayet stars. The fact that WR stars and RSGs rarely occur in the same coeval populations indicates that the mass range of these two populations is different, WR stars originating from more massive stars than RSGs. Single star evolution models predict variations with the metallicity of the number ratios of Type Ibc to Type II supernovae, of Type Ib to Type II and of Type Ic to Type II, which are compatible with observations, provided that many stars leaving a black hole as a remnant produce an observable supernova event.
Meynet, Georges; Georgy, Cyril; Hirschi, Raphael; Maeder, Andr�; Massey, Phil; Przybilla, Norbert; Nieva, M.-Fernanda
Contribution of Thermally-Pulsing Asymptotic Giant Branch and Red Supergiant Starts to the Luminosities of the Magellanic Clouds at 1-24 micrometers.
National Technical Information Service (NTIS)
We present the near-through mid-infrared flux contribution of thermally-pulsing asymptotic giant branch (TP-AGB) and massive red supergiant (RSG) stars to the luminosities of the Large and Small Magellanic Clouds (LMC and SMC, respectively). Combined, the...
J. Melbourne M. L. Boyer
Spatially resolved dusty torus toward the red supergiant WOH G64 in the Large Magellanic Cloud
NASA Astrophysics Data System (ADS)
Aims: We present N-band spectro-interferometric observations of the red supergiant WOH G64 in the Large Magellanic Cloud (LMC) using MIDI at the Very Large Telescope Interferometer (VLTI). While the very high luminosity (� 5 � 105 L?) previously estimated for WOH G64 suggests that it is a very massive star with an initial mass of ~40 M?, its low effective temperature (~3200 K) is in serious disagreement with the current stellar evolution theory. Methods: WOH G64 was observed with VLTI/MIDI using the UT2-UT3 and UT3-UT4 baseline configurations. Results: The dust envelope around WOH G64 has been spatially resolved with a baseline of ~60 m - the first MIDI observations to resolve an individual stellar source in an extragalactic system. The observed N-band visibilities show a slight decrease from 8 to ~10 ?m and a gradual increase longward of ~10 ?m, reflecting the 10 ?m silicate feature in self-absorption. This translates into a steep increase of the uniform-disk diameter from 8 to 10 ?m (from 18 to 26 mas) and a roughly constant diameter above 10 ?m. The visibilities measured at four position angles differing by ~60� but at approximately the same baseline length (~60 m) do not show a noticeable difference, suggesting that the object appears nearly centrosymmetric. The observed N-band visibilities and spectral energy distribution can be reproduced by an optically and geometrically thick silicate torus model viewed close to pole-on. The luminosity of the central star is derived to be � 2.8 � 105 L?, which is by a factor of 2 lower than the previous estimates based on spherical models. We also identify the H2O absorption features at 2.7 and 6 ?m in the spectra obtained with the Infrared Space Observatory and the Spitzer Space Telescope. The 2.7 ?m feature originates in the photosphere and/or the extended molecular layers, while the 6 ?m feature is likely to be of circumstellar origin. Conclusions: The lower luminosity newly derived from our MIDI observations and two-dimensional modeling brings the location of WOH G64 on the H-R diagram in much better agreement with theoretical evolutionary tracks for a 25 M? star. However, the effective temperature is still somewhat too cool for the theory. The low effective temperature of WOH G64 places it very close to or even beyond the Hayashi limit, which implies that this object may be experiencing unstable, violent mass loss. Based on observations made with the Very Large Telescope Interferometer of the European Southern Observatory. Program ID: 076.D-0253, 080.D-0222. This work is based [in part] on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.
Ohnaka, K.; Driebe, T.; Hofmann, K.-H.; Weigelt, G.; Wittkowski, M.
Synchrotron radiation from the winds of O supergiants - Tb = 10 to the 7. 6th K at 60 stellar radii
Results are presented on VLBI measurements of the nonthermal radio components around two O supergiant stars: Cyg OB2 No. 9 and HD 167971. The measurements were used to characterize the brightness temperature of the emission and to measure the size of compact 5-10 mJy components in these stars, reported by Bieging et al. (1989). The sizes found for the 5-10 mJy components are consistent with the free-free wind radii, indicating that the compact companions are not the sources of nonthermal radiation. Results suggest that there is a small fractional population (10 to the -4th to 10 to the -7th) of ultrarelativistic electrons (Teff of about 10 to the 11th K) coexisting with the stellar wind, which emit optically thin synchrotron radiation. This is in agreement with the synchrotron model of White (1985). 21 refs.
Phillips, R.B.; Titus, M.A. (Haystack Observatory, Westford, MA (USA))
An atlas of spectra of B6-A2 hypergiants and supergiants from 4800 to 6700 �
NASA Astrophysics Data System (ADS)
We present an atlas of spectra of 5 emission-line stars: the low-luminosity luminous blue variables (LBVs) HD 168625 and HD 160529, the white hypergiants (and LBV candidates) HD 168607 and AS 314, and the supergiant HD 183143. The spectra were obtained with 2 echelle spectrometers at the 6-m telescope of the Russian Academy of Sciences in the spectral range 4800 to 6700 �, with a resolution of 0.4 �. We have identified 380 spectral lines and diffuse interstellar bands within the spectra. Specific spectral features of the objects are described. The complete atlas and Table 2 are only available in electronic form at the CDS via anonymous ftp to\\ cdsarc.u-strasbg.fr (184.108.40.206) or via\\ http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/1035
Chentsov, E. L.; Ermakov, S. V.; Klochkova, V. G.; Panchuk, V. E.; Bjorkman, K. S.; Miroshnichenko, A. S.
The supergiant amphipod Alicella gigantea (Crustacea: Alicellidae) from hadal depths in the Kermadec Trench, SW Pacific Ocean
NASA Astrophysics Data System (ADS)
Here we provide the first record of the 'supergiant' amphipod Alicella gigantea Chevreux, 1899 (Alicellidae) from the Southern Hemisphere, and extend the known bathymetric range by over 1000 m to 7000 m. An estimated nine individuals were observed across 1500 photographs taken in situ by baited camera at 6979 m in the Kermadec Trench, SW Pacific Ocean. Nine specimens, ranging in length from 102 to 290 mm were recovered by baited trap at depths of 6265 m and 7000 m. Mitochondrial and nuclear DNA sequences obtained indicate a cosmopolitan distribution for the species. Data and observations from the study are used to discuss the reason for gigantism in this species, and its apparently disjunct geographical distribution.
Jamieson, A. J.; Lacey, N. C.; L�rz, A.-N.; Rowden, A. A.; Piertney, S. B.
Distance and Proper Motion Measurement of the Red Supergiant, S Persei, with VLBI H2O Maser Astrometry
NASA Astrophysics Data System (ADS)
We have conducted Very Long Baseline Array phase-referencing monitoring of H2O masers around the red supergiant, S Persei, for six years. We have fitted maser motions to a simple expanding-shell model with a common annual parallax and stellar proper motion, and obtained the annual parallax as 0.413 � 0.017 mas and the stellar proper motion as (-0.49 � 0.23 mas yr-1, -1.19 � 0.20 mas yr-1) in right ascension and declination, respectively. The obtained annual parallax corresponds to the trigonometric distance of 2.42+0.11 -0.09 kpc. Assuming a Galactocentric distance of the Sun of 8.5 kpc, the circular rotational velocity of the local standard of rest at a distance of the Sun of 220 km s-1, and a flat Galactic rotation curve, S Persei is suggested to have a non-circular motion deviating from the Galactic circular rotation for 15 km s-1, which is mainly dominated by the anti-rotation direction component of 12.9 � 2.9 km s-1. This red supergiant is thought to belong to the OB association, Per OB1, so that this non-circular motion is representative of a motion of the OB association in the Milky Way. This non-circular motion is somewhat larger than that explained by the standard density-wave theory for a spiral galaxy and is attributed to either a cluster shuffling of the OB association, or to non-linear interactions between non-stationary spiral arms and multi-phase interstellar media. The latter comes from a new view of a spiral arm formation in the Milky Way suggested by recent large N-body/smoothed particle hydrodynamics numerical simulations.
Asaki, Y.; Deguchi, S.; Imai, H.; Hachisuka, K.; Miyoshi, M.; Honma, M.
On the magnetic structure and wind parameter profiles of Alfv�n wave driven winds in late-type supergiant stars
NASA Astrophysics Data System (ADS)
Cool stars at giant and supergiant evolutionary phases present low-velocity and high-density winds, responsible for the observed high mass-loss rates. Although presenting high luminosities, radiation pressure on dust particles is not sufficient to explain the wind acceleration process. Among the possible solutions to this still unsolved problem, Alfv�n waves are, probably, the most interesting for their high efficiency in transfering energy and momentum to the wind. Typically, models of Alfv�n wave driven winds result in high-velocity winds if they are not highly damped. In this work, we determine self-consistently the magnetic field geometry and solve the momentum, energy and mass conservation equations, to demonstrate that even a low-damped Alfv�n wave flux is able to reproduce the low-velocity wind. We show that the magnetic flux tubes expand with a super-radial factor of S > 30 near the stellar surface, larger than that used in previous semi-empirical models. The rapid expansion results in a strong spatial dilution of the wave flux. We obtained the wind parameter profiles for a typical supergiant star of 16 Msolar. The wind is accelerated in a narrow region, coincident with the region of high divergence of the magnetic field lines, up to 100 km s-1. For the temperature, we obtained a slight decrease near the surface for low-damped waves, because the wave heating mechanism is less effective than the radiative losses. The peak temperature occurs at r ~= 1.5r0 reaching 6000 K. Propagating outwards, the wind cools down mainly due to adiabatic expansion.
Falceta-Gon�alves, D.; Vidotto, A. A.; Jatenco-Pereira, V.
Revisiting the absolute-magnitude calibration of F-type supergiants and bright giants as a function of the equivalent width of the OI?7774� triplet
NASA Astrophysics Data System (ADS)
We reduce the published measurements of the equivalent width of the oxygen triplet (Oi?7774�) to a single system and combine the resulting homogenized indices with revised Hipparcos parallaxes to derive the MK versus log[W(Oi?7774�)] absolute-magnitude calibration for bright F-type giants and supergiants and use the resulting calibration to estimate both the distance to the Large Magellanic Cloud and the parameters of the Galactic rotation curve.
Dambis, A. K.
Swift\\/XRT observes the fifth outburst of the periodic supergiant fast X-ray transient IGR J11215-5952
Context: The hard X-ray transient source IGR J11215-5952 was discovered in April 2005 with INTEGRAL and is a confirmed member of the new class of high mass X-ray binaries, the supergiant fast X-ray transients (SFXTs). Archival INTEGRAL data and RXTE observations have shown that the outbursts occur with a periodicity of ~330 days. Thus, IGR J11215-5952 is the first SFXT
P. Romano; L. Sidoli; V. Mangano; S. Mereghetti; G. Cusumano
Swift\\/XRT monitoring of the supergiant fast X-ray transient IGR J18483-0311 for an entire orbital period
IGR J18483-0311 is an X-ray pulsar with transient X-ray activity, belonging to the new class of high-mass X-ray binaries called supergiant fast X-ray transients. This system is one of the two members of this class, together with IGR J11215-5952, where both the orbital (18.52 d) and spin period (21 s) are known. We report on the first complete monitoring of
P. Romano; L. Sidoli; L. Ducci; G. Cusumano; V. La Parola; C. Pagani; K. L. Page; J. A. Kennea; D. N. Burrows; N. Gehrels; V. Sguera; A. Bazzano
Wind structure of late B supergiants. I. Multiline analyses of near-surface and wind structure in HD 199 478 (B8 Iae)
Aims: We provide a quantitative analysis of time-variable phenomena in the photospheric, near-star, and outflow regions of the late-B supergiant (SG) HD 199 478. This study aims to provide new perspectives on the nature of outflows in late-B SGs and on the influence of large-scale structures rooted at the stellar surface. Methods: The analysis is based primarily on optical spectroscopic
N. Markova; R. K. Prinja; H. Markov; I. Kolka; N. Morrison; J. Percy; S. Adelman
Short time-scale spectral variability in the A0 supergiant HD 92207 and the importance of line profile variations for the interpretation of FORS 2 spectropolarimetric observations
NASA Astrophysics Data System (ADS)
Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD 92207 using FOcal reducer low dispersion spectrograph (FORS) 2 in spectropolarimetric mode indicated the presence of a longitudinal magnetic field of the order of a few hundred gauss. Assuming the ideal case of a non-variable star, this discovery has recently been questioned in one work trying to demonstrate the importance of non-photon noise in FORS 2 observations. The assumption of non-variability of HD 92207 can, however, not be held since substantial profile variations of diverse lines on a time-scale of minutes or maybe even a fraction of a minute are detected in FORS 2 spectra. The presence of short-term spectral variability in blue supergiants, which are considered as Type II supernova progenitors, has not been a subject of systematic studies before and is critical for the current theoretical understanding of their physics. Given the detected short-term variability, the question of the presence of a magnetic field cannot be answered without proper modelling of the impact of such a variability on the measurements of the magnetic field. Since the short-term periodicity does not fit into the currently known domain of non-radially pulsating supergiants, its confirmation is of great importance for models of stellar evolution.
Hubrig, S.; Sch�ller, M.; Kholtygin, A. F.
Determination of the Masses of the Hyades Binary VA351 and the Circumstellar Structure of the Supergiant VV Cep {HD 208816}
NASA Astrophysics Data System (ADS)
A search with Hubble Space Telescope Fine Guidance Sensor 3 in TRANS mode of 36 probable Hyades cluster members in the magnitude range V=10--15 has yielded nine certain binary detections. Subsequent observations have shown that among these, VA351 has a period of approximately 5 years. We propose to carry out astrometry of this faint Hyades binary with FGS in a combination of POS and TRANS modes. Such new observations, combined with FGS astrometry already in hand, and with orbital radial velocity measures, will yield masses and absolute magnitudes of this low- luminosity Hyades members independent of the kinematic mean cluster distance and with an accuracy of 5 percent or better. VV Cep is a eclipsing spectroscopic binary consisting of a very massive supergiant and a hot main sequence companion. At the time requested in this proposal, the hot companion will be eclipsed by the supergiant, thus affording the opportunity to study at high angular resolution the supergiant star and its extended envelope.
Franz, Otto
HST Studies of the Chromospheres, Wind, and Mass-Loss Rates of Cool Giant and Supergiant Stars
NASA Technical Reports Server (NTRS)
UV spectra of K-M giant and supergiant stars and of carbon stars have been acquired with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). These spectra have been used to measure chromospheric flow and turbulent velocities, study the acceleration of their stellar winds, acquire constraints on their outer atmospheric structure, and enable estimates of their mass-loss rates. Results from our observations of the giant stars Gamma Dra (K5 III hybrid), Alpha Tau (K5 III), Gamma Cru (M3.4 III), Mu Gem (M3 IIIab), and 30 Her (MG III), the supergiants Alpha Ori (M2 Iab) and Lambda Vel (K5 Ib), and the carbon stars TX Psc (NO; C6,2) and TW Hor (NO; C7,2) will be summarized and compared. The high resolution and wavelength accuracy of these data have allowed the direct measurement of the acceleration of the stellar winds in the chromospheres of several of these stars (from initial velocities of 3-9 km/s to upper velocities of 15-25 km/s) and of the chromospheric macroturbulence (-25-35 km/s). The high signal-to-noise and large dynamic range of these spectra have allowed the detection and identification of numerous new emission features, including weak C IV emission indicative of hot transition-region plasma in the non-coronal giant Alpha Tau, many new fluorescent lines of Fe II, and the first detection of fluorescent molecular hydrogen emission and of Ca II recombination lines in the UV spectrum of a giant star. The UV spectrum of two carbon stars have been studied with unprecedented resolution and reveal extraordinarily complicated Mg II lines nearly smothered by circumstellar absorptions. Finally, comparison of synthetic UV emission line profiles computed with the Lamers et al. (1987) Sobolev with Exact Integration (SEI) code with observations of chromospheric emission lines overlain with wind absorption features provides estimates of the mass-loss rates for four of these stars.
Carpenter, Kenneth G.
Revised Stellar Temperatures for Magellanic Cloud O Supergiants from Far Ultraviolet Spectroscopic Explorer and Very Large Telescope UV-Visual Echelle Spectrograph Spectroscopy
NASA Astrophysics Data System (ADS)
We have undertaken quantitative analysis of four LMC and SMC O4-9.7 extreme supergiants using far-ultraviolet FUSE, ultraviolet IUE/Hubble Space Telescope, and optical Very Large Telescope UV-Visual Echelle Spectrograph spectroscopy. Extended, non-LTE model atmospheres that allow for the consistent treatment of line blanketing, developed by Hillier & Miller, are used to analyze wind and photospherics spectral features simultaneously. Using H? to constrain mass-loss rates, He I-He II photospheric lines reveal stellar temperatures that are systematically (5-7.5 kK) and substantially (15%-20%) lower than previously derived from unblanketed, plane-parallel, non-LTE photospheric studies. We have confidence in these revisions since derived temperatures generally yield consistent fits across the entire 912-7000 � observed spectral range. In particular, we are able to resolve the UV-optical temperature discrepancy identified for AzV 232 (O7 Iaf+) in the SMC by Fullerton and coworkers. The temperature and abundance sensitivity of far-ultraviolet, UV, and optical lines are discussed. ``Of'' classification criteria are directly linked to (strong) nitrogen enrichment (via N III ?4097) and (weak) carbon depletion (via C III ??4647-4651), providing evidence for mixing of unprocessed and CNO-processed material at their stellar surfaces. Oxygen abundances are more difficult to constrain, except via O II lines in the O9.7 supergiant, for which it is also found to be somewhat depleted. Unfortunately, He/H is very difficult to determine in individual O supergiants because of uncertainties in microturbulence and the atmospheric scale height. The effect of wind clumping is also investigated, for which P V ??1118-1128 potentially provides a useful diagnostic in O star winds, unless phosphorus can be independently demonstrated to be underabundant relative to other heavy elements. Revised stellar properties affect existing calibrations of (1) Lyman continuum photons-a factor of 2 lower for the O4 supergiant-and (2) kinetic energy released into the ISM by O supergiants. Our results also have importance for the calibration of the wind momentum-luminosity relationship for OB stars, particularly since the stars studied here are among the visually brightest OB stars in external galaxies. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by Johns Hopkins University under NASA contract NAS 5-32985. Also based in part on observations collected at the European Southern Observatory Very Large Telescopes in programs 65.H-0705 and 67.D-0238, plus archival data obtained with the NASA-ESA Hubble Space Telescope and NASA-ESA-PPARC International Ultraviolet Explorer.
Crowther, P. A.; Hillier, D. J.; Evans, C. J.; Fullerton, A. W.; De Marco, O.; Willis, A. J.
Swift/XRT orbital monitoring of the candidate supergiant fast X-ray transient IGR J17354-3255
NASA Astrophysics Data System (ADS)
We report on the Swift/X-ray Telescope (XRT) monitoring of the field of view around the candidate supergiant fast X-ray transient (SFXT) IGR J17354-3255, which is positionally associated with the AGILE/GRID gamma-ray transient AGL J1734-3310. Our observations, which cover 11 days for a total on-source exposure of ~24 ks, span 1.2 orbital periods (Porb = 8.4474 d) and are the first sensitive monitoring of this source in the soft X-rays. These new data allow us to exploit the timing variability properties of the sources in the field to unambiguously identify the soft X-ray counterpart of IGR J17354-3255. The soft X-ray light curve shows a moderate orbital modulation and a dip. We investigated the nature of the dip by comparing the X-ray light curve with the prediction of the Bondi-Hoyle-Lyttleton accretion theory, assuming both spherical and nonspherical symmetry of the outflow from the donor star. We found that the dip cannot be explained with the X-ray orbital modulation. We propose that an eclipse or the onset of a gated mechanism is the most likely explanation for the observed light curve.
Ducci, L.; Romano, P.; Esposito, P.; Bozzo, E.; Krimm, H. A.; Vercellone, S.; Mangano, V.; Kennea, J. A.
Sharpest views of Betelgeuse reveal how supergiant stars lose mass-Unveiling the true face of a behemoth
NASA Astrophysics Data System (ADS)
Using different state-of-the-art techniques on ESO's Very Large Telescope, two independent teams of astronomers have obtained the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate. Betelgeuse - the second brightest star in the constellation of Orion (the Hunter) - is a red supergiant, one of the biggest stars known, and almost 1000 times larger than our Sun [1]. It is also one of the most luminous stars known, emitting more light than 100000 Suns. Such extreme properties foretell the demise of a short-lived stellar king. With an age of only a few million years, Betelgeuse is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be seen easily from Earth, even in broad daylight. Red supergiants still hold several unsolved mysteries. One of them is just how these behemoths shed such tremendous quantities of material - about the mass of the Sun - in only 10 000 years. Two teams of astronomers have used ESO's Very Large Telescope (VLT) and the most advanced technologies to take a closer look at the gigantic star. Their combined work suggests that an answer to the long-open mass-loss question may well be at hand. The first team used the adaptive optics instrument, NACO, combined with a so-called "lucky imaging" technique, to obtain the sharpest ever image of Betelgeuse, even with Earth's turbulent, image-distorting atmosphere in the way. With lucky imaging, only the very sharpest exposures are chosen and then combined to form an image much sharper than a single, longer exposure would be. The resulting NACO images almost reach the theoretical limit of sharpness attainable for an 8-metre telescope. The resolution is as fine as 37 milliarcseconds, which is roughly the size of a tennis ball on the International Space Station (ISS), as seen from the ground. "Thanks to these outstanding images, we have detected a large plume of gas extending into space from the surface of Betelgeuse," says Pierre Kervella from the Paris Observatory, who led the team. The plume extends to at least six times the diameter of the star, corresponding to the distance between the Sun and Neptune. "This is a clear indication that the whole outer shell of the star is not shedding matter evenly in all directions," adds Kervella. Two mechanisms could explain this asymmetry. One assumes that the mass loss occurs above the polar caps of the giant star, possibly because of its rotation. The other possibility is that such a plume is generated above large-scale gas motions inside the star, known as convection - similar to the circulation of water heated in a pot. To arrive at a solution, astronomers needed to probe the behemoth in still finer detail. To do this Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used interferometry. With the AMBER instrument on ESO's Very Large Telescope Interferometer, which combines the light from three 1.8-metre Auxiliary Telescopes of the VLT, the astronomers obtained observations as sharp as those of a giant, virtual 48-metre telescope. With such superb resolution, the astronomers were able to detect indirectly details four times finer still than the amazing NACO images had already allowed (in other words, the size of a marble on the ISS, as seen from the ground). "Our AMBER observations are the sharpest observations of any kind ever made of Betelgeuse. Moreover, we detected how the gas is moving in different areas of Betelgeuse's surface ? the first time this has been done for a star other than the Sun", says Ohnaka. The AMBER observations revealed that the gas in Betelgeuse's atmosphere is moving vigorously up and down, and that these bubbles are as large as the supergiant star itself. Their unrivalled observations have led
Low-amplitude rotational modulation rather than pulsations in the CoRoT B-type supergiant HD 46769
NASA Astrophysics Data System (ADS)
Aims: We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 (V = 5.79). We also attempt to detect a magnetic field in the target. Methods: We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assuming a dipole field. Results: In the CoRoT data, we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 � 2 km s-1 and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. Conclusions: The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. Based on CoRoT space-based photometric data; the CoRoT space mission was developed and operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations collected at La Silla Observatory, ESO (Chile) with the HARPS spectrograph at the 3.6 m telescope, under programme LP185.D-0056. Based on observations obtained with the HERMES spectrograph attached to the 1.2 m Mercator telescope, which is supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la Recherche Scientific (FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Gen�ve, Switzerland, and the Th�ringer Landessternwarte Tautenburg, Germany. Based on observations obtained with the Narval spectropolarimeter at the Observatoire du Pic du Midi (France), which is operated by the Institut National des Sciences de l'Univers (INSU).
Aerts, C.; Sim�n-D�az, S.; Catala, C.; Neiner, C.; Briquet, M.; Castro, N.; Schmid, V. S.; Scardia, M.; Rainer, M.; Poretti, E.; P�pics, P. I.; Degroote, P.; Bloemen, S.; �stensen, R. H.; Auvergne, M.; Baglin, A.; Baudin, F.; Michel, E.; Samadi, R.
Periodic mass-loss episodes due to an oscillation mode with variable amplitude in the hot supergiant HD 50064
NASA Astrophysics Data System (ADS)
Aims: We aim to interpret the photometric and spectroscopic variability of the luminous blue variable supergiant HD 50064 (V = 8.21). Methods: CoRoT space photometry and follow-up high-resolution spectroscopy with a time base of 137 d and 169 d, respectively, was gathered, analysed, and interpreted using standard time series analysis and light curve modelling methods, as well as spectral line diagnostics. Results: The space photometry reveals one period of 37 d, which undergoes a sudden amplitude change with a factor 1.6. The pulsation period is confirmed in the spectroscopy, which additionally reveals metal line radial velocity values differing by 30 km s-1 depending on the spectral line and on the epoch. We estimate Teff 13 500 K, log g 1.5 from the equivalent width of Si lines. The Balmer lines reveal that the star undergoes episodes of changing mass loss on a time scale similar to the changes in the photometric and spectroscopic variability, with an average value of log dot{M} ? -5 (in M_? yr-1). We tentatively interpret the 37 d period as the result of a strange mode oscillation. Based on high-resolution spectroscopy assembled with the CORALIE spectrograph attached to the 1.2 m Euler telescope at La Silla, Chile and on CoRoT space-based photometry. The CoRoT space mission was developed and is operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.Postdoctoral Fellow of the Fund for Scientific Research of Flanders (FWO), Belgium.
Aerts, C.; Lefever, K.; Baglin, A.; Degroote, P.; Oreiro, R.; Vu?kovi?, M.; Smolders, K.; Acke, B.; Verhoelst, T.; Desmet, M.; Godart, M.; Noels, A.; Dupret, M.-A.; Auvergne, M.; Baudin, F.; Catala, C.; Michel, E.; Samadi, R.
Crossing the Yellow Void: Spatially Resolved Spectroscopy of the Post-Red Supergiant IRC +10420 and Its Circumstellar Ejecta
NASA Astrophysics Data System (ADS)
IRC +10420 is one of the extreme hypergiant stars that define the empirical upper luminosity boundary in the H-R diagram. During their post-red supergiant evolution, these massive stars enter a temperature range (6000-9000 K) of increased dynamical instability, high mass loss, and increasing opacity, a semiforbidden region that de Jager and his collaborators have called the ``yellow void.'' We report HST/STIS spatially resolved spectroscopy of IRC +10420 and its reflection nebula with some surprising results. Long-slit spectroscopy of the reflected spectrum allows us to effectively view the star from different directions. Measurements of the double-peaked H? emission profile show a uniform outflow of gas in a nearly spherical distribution, contrary to previous models with an equatorial disk or bipolar outflow. Based on the temperature and mass-loss rate estimates that are usually quoted for this object, the wind is optically thick to the continuum at some and possibly all wavelengths. Consequently, the observed variations in apparent spectral type and inferred temperature are changes in the wind and do not necessarily mean that the underlying stellar radius and interior structure are evolving on such a short timescale. To explain the evidence for simultaneous outflow and infall of material near the star, we propose a ``rain'' model, in which blobs of gas condense in regions of lowered opacity outside the dense wind. With the apparent warming of its wind, the recent appearance of strong emission, and a decline in the mass-loss rate, IRC +10420 may be about to shed its opaque wind, cross the yellow void, and emerge as a hotter star. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Humphreys, Roberta M.; Davidson, Kris; Smith, Nathan
The Orbit and Properties of the BD+60 73 + IGRJ00370+612 Supergiant X-Ray Binary
NASA Astrophysics Data System (ADS)
Spectrograms of the blue and H alpha regions of BD+60 73 obtained with the Cassegrain spectrograph on the David Dunlap Observatory 1.88 m telescope have been measured for radial velocities. These measures confirm that BD+60 73 is a single-line spectroscopic binary with the same period, 15.665 d, as the x-ray flux variations of IGRJ00370+612. The x-ray maxima occur at or just after the time of periastron passage, even though the eccentricity e=0.37 does not seem large enough to produce a large increase in the mass flux at the position of the compact object at the time of periastron passage. The mass function combined with a plausible range of possible masses for a neutron star companion yields primary masses within the range expected for the spectral type of BD+60 73. The compact companion cannot be a black hole unless the supergiant has an exceptionally high mass for its B1Ib spectral type or the inclination of the orbit is very low. The H alpha line shows weak, variable emission, but we have insufficient data to test whether these variations are correlated with orbital phase. We note, as have other authors, that BD+60_73 is projected on the sky within the bounds of Cas OB5. It also lies close to the "adolescent" supernova remnant CTB1. However, the binary system has a radial velocity of approximately -40 km/s with respect to Cas OB5.
Bolton, C. T.; Grunhut, J. H.
Imaging the spinning gas and dust in the disc around the supergiant A[e] star HD 62623
NASA Astrophysics Data System (ADS)
Context. To progress in the understanding of evolution of massive stars one needs to constrain the mass-loss and determine the phenomenon responsible for the ejection of matter an its reorganization in the circumstellar environment Aims: In order to test various mass-ejection processes, we probed the geometry and kinematics of the dust and gas surrounding the A[e] supergiant HD 62623. Methods: We used the combined high spectral and spatial resolution offered by the VLTI/AMBER instrument. Thanks to a new multi-wavelength optical/IR interferometry imaging technique, we reconstructed the first velocity-resolved images with a milliarcsecond resolution in the infrared domain. Results: We managed to disentangle the dust and gas emission in the HD 62623 circumstellar disc. We measured the dusty disc inner rim, i.e. 6 mas, constrained the inclination angle and the position angle of the major-axis of the disc. We also measured the inner gaseous disc extension (2 mas) and probed its velocity field thanks to AMBER high spectral resolution. We find that the expansion velocity is negligible, and that Keplerian rotation is a favoured velocity field. Such a velocity field is unexpected if fast rotation of the central star alone is the main mechanism of matter ejection. Conclusions: As the star itself seems to rotate below its breakup-up velocity, rotation cannot explain the formation of the dense equatorial disc. Moreover, as the expansion velocity is negligible, radiatively driven wind is also not a suitable explanation to explain the disc formation. Consequently, the most probable hypothesis is that the accumulation of matter in the equatorial plane is due to the presence of the spectroscopic low mass companion. Based on CNRS Guaranteed Time Observations with ESO telescopes at the Paranal Observatory under program 084.D-0355, and on Director's Discretionary Time, 284.D-5059. Feasibility was assessed using open time, 083.C-0621.
Millour, F.; Meilland, A.; Chesneau, O.; Stee, Ph.; Kanaan, S.; Petrov, R.; Mourard, D.; Kraus, S.
On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants
NASA Astrophysics Data System (ADS)
We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength Spectrometer spectra of 217 oxygen-rich asymptotic giant branch and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds, and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 ?m. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of �10-9 M? yr-1. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-?m feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-?m band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.
Jones, O. C.; Kemper, F.; Sargent, B. A.; McDonald, I.; Gielen, C.; Woods, Paul M.; Sloan, G. C.; Boyer, M. L.; Zijlstra, A. A.; Clayton, G. C.; Kraemer, K. E.; Srinivasan, S.; Ruffle, P. M. E.
Blue Supergiant Model for Ultra-long Gamma-Ray Burst with Superluminous-supernova-like Bump
NASA Astrophysics Data System (ADS)
Long gamma-ray bursts (LGRBs) have a typical duration of ~30 s, and some of them are associated with hypernovae, such as Type Ic SN 1998bw. Wolf-Rayet stars are the most plausible LGRB progenitors, since the free fall time of the envelope is consistent with the duration, and the natural outcome of the progenitor is a Type Ic SN. While a new population of ultra-long GRBs (ULGRBs), GRB 111209A, GRB 101225A, and GRB 121027A, has a duration of ~104 s, two of them are accompanied by superluminous-supernova-like (SLSN-like) bumps, which are <~ 10 times brighter than typical hypernovae. Wolf-Rayet progenitors cannot explain ULGRBs because of durations that are too long and SN-like bumps that are too bright. A blue supergiant (BSG) progenitor model, however, can explain the duration of ULGRBs. Moreover, SLSN-like bumps can be attributed to the so-called cocoon fireball photospheric emissions (CFPEs). Since a large cocoon is inevitably produced during the relativistic jet piercing though the BSG envelope, this component can be smoking gun evidence of the BSG model for ULGRBs. In this paper, we examine u-, g-, r-, i-, and J-band light curves of three ULGRBs and demonstrate that they can be fitted quite well by our BSG model with the appropriate choices of the jet opening angle and the number density of the ambient gas. In addition, we predict that for 121027A, SLSN-like bump could have been observed for ~20-80 days after the burst. We also propose that some SLSNe might be CFPEs of off-axis ULGRBs without visible prompt emissions.
Nakauchi, Daisuke; Kashiyama, Kazumi; Suwa, Yudai; Nakamura, Takashi
IGR J17544-2619 in Depth With Suzaku: Direct Evidence for Clumpy Winds in a Supergiant Fast X-ray Transient
NASA Astrophysics Data System (ADS)
We present direct evidence for dense clumps of matter in the companion wind in a Supergiant Fast X-ray Transient (SFXT) binary. This is seen as a brief period of enhanced absorption during one of the bright, fast flares that distinguish these systems. The object under study was IGR J17544-2619, and a total of 236 ks of data were accumulated with the Japanese satellite Suzaku. The activity in this period spans a dynamic range of almost 104 in luminosity and gives a detailed look at SFXT behavior.
Rampy, Rachel A.; Smith, David M.; Negueruela, Ignacio
A Suzaku X-ray Observation of One Orbit of the Supergiant Fast X-ray Transient IGR J16479-4514
NASA Technical Reports Server (NTRS)
We report on a 250 ks long X-ray observation of the supergiant fast X-ray transient (SFXT) IGR J16479-4514 performed with Suzaku in 2012 February. During this observation, about 80% of the short orbital period (P(sub orb) approximates 3.32 days) was covered as continuously as possible for the first time. The source light curve displays variability of more than two orders of magnitude, starting with a very low emission state (10(exp -13) erg / sq cm/s; 1-10 keV) lasting the first 46 ks, consistent with being due to the X-ray eclipse by the supergiant companion. The transition to the uneclipsed X-ray emission is energy dependent. Outside the eclipse, the source spends most of the time at a level of 6-7X10)(exp-12) erg/sq. cm/s) punctuated by two structured faint flares with a duration of about 10 and 15 ks, respectively, reaching a peak flux of 3-4X10(exp -11) erg/sq. cm./S, separated by about 0.2 in orbital phase. Remarkably, the first faint flare occurs at a similar orbital phase of the bright flares previously observed in the system. This indicates the presence of a phase-locked large scale structure in the supergiant wind, driving a higher accretion rate onto the compact object. The average X-ray spectrum is hard and highly absorbed, with a column density, NH, of 10*exp 23)/sq cm, clearly in excess of the interstellar absorption. There is no evidence for variability of the absorbing column density, except that during the eclipse, where a less absorbed X-ray spectrum is observed. A narrow Fe K-alpha emission line at 6.4 keV is viewed along the whole orbit, with an intensity which correlates with the continuum emission above 7 keV. The scattered component visible during the X-ray eclipse allowed us to directly probe the wind density at the orbital separation, resulting in rho(sub w)=7X10(exp -14) g/cubic cm. Assuming a spherical geometry for the supergiant wind, the derived wind density translates into a ratio M(sub w)/v(sub infinity) = 7X10(exp -17) Solar M/km which, assuming terminal velocities in a large range 500-3000 km/s, implies an accretion luminosity two orders of magnitude higher than that observed. As a consequence, a mechanism should be at work reducing the mass accretion rate. Different possibilities are discussed.
Sidoli, L.; Esposito, P.; Sguera, V.; Bodaghee, A.; Tomsick, J. A.; Pottschmidt, K.; Rodriguez, J.; Ramano, P.; Wilms, J.
Discovery of an eccentric 30 day period in the supergiant X-ray binary SAX J1818.6-1703 with INTEGRAL
NASA Astrophysics Data System (ADS)
Context: SAX J1818.6-1703 is a flaring transient X-ray source serendipitously discovered by BeppoSAX in 1998 during an observation of the Galactic centre. The source was identified as a high-mass X-ray binary with an OB supergiant companion (SGXB). Displaying short and bright flares and an unusually very low quiescent level implying an intensity dynamical range as large as 103-4, the source was classified as a supergiant fast X-ray transient (SFXT). Aims: The mechanism triggering the different temporal behaviour observed between the classical SGXBs and the recently discovered class of SFXTs is still debated. The discovery of long orbits (>15 d) should help to discriminate between emission models and bring constraints. Methods: We analysed archival INTEGRAL data on SAX J1818.6-1703. We built short- and long-term light curves and performed a timing analysis in order to study the temporal behaviour of SAX J1818.6-1703 on different time scales. Results: INTEGRAL revealed an unusually long orbital period of 30.0 � 0.2 d and an elapsed accretion phase of ~6 d in the transient SGXB SAX J1818.6-1703. This implies an elliptical orbit and constraints the possible supergiant spectral type between B0.5-1I with eccentricities e ~ 0.3-0.4 (for the average fundamental parameters of supergiant stars). During the accretion phase, the source behaved like a classical SGXB. The huge variations of the observed X-ray flux can be explained through accretion of macro-clumps formed within the stellar wind. Our analysis strengthens the model which predicts that SFXTs behave as SGXBs but with different orbital parameters, thus different temporal behaviour. Discovery first reported at the 7th INTEGRAL workshop (Zurita Heras et al., in press). Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA.
Zurita Heras, J. A.; Chaty, S.
Wind Variability of B Supergiants. No. 1; The Rapid Rotator HD 64760 (B0.5 Ib)
NASA Technical Reports Server (NTRS)
We present the results of a 6 day time series of observations of the rapidly rotating B0.5 Ib star HD 64760. We point out several reasons why such intermediate luminosity B supergiants are ideal targets for wind variability studies and then present our results that show the following: continuous wind activity throughout the 6 day run with the wind never in steady state for more than a few hr; wind variability very near nu = 0 km sec(exp -1) in the resonance lines from the lower ionization stages (Al III and C II); a distinct correlation between variability in the Si III ; lambda(lambda)1300 triplets, the strong C III (lambda)1247 singlet, and the onset of extremely strong wind activity, suggesting a connection between photospheric and wind activity; long temporal coherence in the behavior of the strong absorption events; evidence for large-scale spatial coherence, implied by a whole scale, simultaneous weakening in the wind absorption over a wide range in velocities; and ionization variability in the wind accompanying the largest changes in the absorption strengths of the wind lines. In addition, modeling of the wind lines provides the following information about the state the wind in HD 64760. The number of structures on the portion of a constant velocity surface occulting the stellar disk at a particular time must be quite small, while the number on the entire constant velocity surface throughout the wind must be large. The escape probability at low velocity is overestimated by a normal beta approx. 1 velocity law, perhaps due to the presence of low-velocity shocks deep in the wind or a shallow velocity gradient at low velocity. Estimates of the ionization structure in the wind indicate that the ionization ratios are not those expected from thermal equilibrium wind models or from an extrapolation of previous O star results. The large observed q(N V)/q(Si IV) ratio is almost certainly due to distributed X-rays, but the level of ionization predicted by distributed X-ray wind models is inconsistent with the predicted mass-loss rate. Thus, it is impossible to reconcile the observed ionization ratios and the predicted mass-loss rate within the framework of the available models.
Massa, Derck; Prinja, Raman K.; Fullerton, Alexander W.
The atmospheric structure and fundamental parameters of the red supergiants AH Scorpii, UY Scuti, and KW Sagittarii
NASA Astrophysics Data System (ADS)
Aims: We present the atmospheric structure and the fundamental properties of the red supergiants (RSGs) AH Sco, UY Sct, and KW Sgr based on VLTI/AMBER observations. Methods: We carried out spectro-interferometric observations of AH Sco, UY Sct, and KW Sgr in the near-infrared K band (1.92-2.47 ?m) with the VLTI/AMBER instrument with spatial and spectral resolutions of 3 milliarcsec and 1500, respectively, and compared the data to a new grid of hydrostatic PHOENIX model atmospheres. Results: In our visibility data, we observe molecular layers of water and CO in extended atmospheres. For a uniform disk modeling, we observe size increases at the water band centered at 1.9 ?m of 10% to 25% and at the CO bandheads at 2.3-2.5 ?m of 20%-35% with respect to the near-continuum bandpass at around 2.20 ?m. Our near-infrared spectra of AH Sco, UY Sct, and KW Sgr are well reproduced by the PHOENIX model atmospheres. The continuum visibility values are consistent with a limb-darkened disk as predicted by the PHOENIX models. However, the model visibilities do not predict the large observed extensions of the molecular layers. Comparing the continuum visibility values to PHOENIX models, we estimate the Rosseland-mean photospheric angular diameters of AH Sco, UY Sct, and KW Sgr to be 5.81 � 0.15 mas, 5.48 � 0.10 mas, and 3.91 � 0.25 mas, respectively. Together with the distance and the spectro-photometry, we calculate radii of 1411 � 124 R? for AH Sco, 1708 � 192 R? for UY Sct, and 1009 � 142 R? for KW Sgr and effective temperatures of 3682 � 190 K for AH Sco, 3365 � 134 K for UY Sct, and 3720 � 183 K for KW Sgr. Conclusions: AH Sco, UY Sct, and KW Sgr exhibit extended atmospheric layers of H2O and CO. The PHOENIX atmosphere models predict the spectra and the continuum visibility values, but cannot reproduce the large extensions of the molecular layers. This indicates that the opacities of the molecular bands are included, but that the model atmospheres are too compact compared to the observations. The observed extended layers may be levitated by processes such as pulsation or convection, which are not included in the hydrostatic atmospheric models. The location of the targets in the HR-diagram is confirmed to be close to, and possibly slightly to the right of, the Hayashi limit of recent evolutionary tracks corresponding to masses between about 20 M? and 40 M?.
Arroyo-Torres, B.; Wittkowski, M.; Marcaide, J. M.; Hauschildt, P. H.
Luminous and Variable Stars in M31 and M33. II. Luminous Blue Variables, Candidate LBVs, Fe II Emission Line Stars, and Other Supergiants
NASA Astrophysics Data System (ADS)
An increasing number of non-terminal eruptions are being found in the numerous surveys for optical transients. Very little is known about these giant eruptions, their progenitors and their evolutionary state. A greatly improved census of the likely progenitor class, including the most luminous evolved stars, the luminous blue variables (LBVs), and the warm and cool hypergiants is now needed for a complete picture of the final pre-supernova stages of very massive stars. We have begun a survey of the evolved and unstable luminous star populations in several nearby resolved galaxies. In this second paper on M31 and M33, we review the spectral characteristics, spectral energy distributions, circumstellar ejecta, and evidence for mass loss for 82 luminous and variable stars. We show that many of these stars have warm circumstellar dust including several of the Fe II emission line stars, but conclude that the confirmed LBVs in M31 and M33 do not. The confirmed LBVs have relatively low wind speeds even in their hot, quiescent or visual minimum state compared to the B-type supergiants and Of/WN stars which they spectroscopically resemble. The nature of the Fe II emission line stars and their relation to the LBV state remains uncertain, but some have properties in common with the warm hypergiants and the sgB[e] stars. Several individual stars are discussed in detail. We identify three possible candidate LBVs and three additional post-red supergiant candidates. We suggest that M33-013406.63 (UIT301,B416) is not an LBV/S Dor variable, but is a very luminous late O-type supergiant and one of the most luminous stars or pair of stars in M33. Based on observations with the Multiple Mirror Telescope, a joint facility of the Smithsonian Institution and the University of Arizona and on observations obtained with the Large Binocular Telescope (LBT), an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia.
Humphreys, Roberta M.; Weis, Kerstin; Davidson, Kris; Bomans, D. J.; Burggraf, Birgitta
GHRS Observations of Cool, Low-Gravity Stars. V. The Outer Atmosphere and Wind of the Nearby K Supergiant ? Velorum
NASA Astrophysics Data System (ADS)
UV spectra of ? Velorum taken with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope are used to probe the structure of the outer atmospheric layers and wind and to estimate the mass-loss rate from this K5 Ib-II supergiant. VLA radio observations at ?=3.6 cm are used to obtain an independent check on the wind velocity and mass-loss rate inferred from the UV observations. Parameters of the chromospheric structure are estimated from measurements of UV line widths, positions, and fluxes and from the UV continuum flux distribution. The ratios of optically thin C II] emission lines indicate a mean chromospheric electron density of logNe~8.9+/-0.2 cm-3. The profiles of these lines indicate a chromospheric turbulence (v0~25-36 km s-1), which greatly exceeds that seen in either the photosphere or wind. The centroids of optically thin emission lines of Fe II and of the emission wings of self-reversed Fe II lines indicate that they are formed in plasma approximately at rest with respect to the photosphere of the star. This suggests that the acceleration of the wind occurs above the chromospheric regions in which these emission line photons are created. The UV continuum detected by the GHRS clearly traces the mean flux-formation temperature as it increases with height in the chromosphere from a well-defined temperature minimum of 3200 K up to about 4600 K. Emission seen in lines of C III] and Si III] provides evidence of material at higher than chromospheric temperatures in the outer atmosphere of this noncoronal star. The photon-scattering wind produces self-reversals in the strong chromospheric emission lines, which allow us to probe the velocity field of the wind. The velocities to which these self-absorptions extend increase with intrinsic line strength, and thus height in the wind, and therefore directly map the wind acceleration. The width and shape of these self-absorptions reflect a wind turbulence of ~9-21 km s-1. We further characterize the wind by comparing the observations with synthetic profiles generated with the Lamers et al. Sobolev with Exact Integration (SEI) radiative transfer code, assuming simple models of the outer atmospheric structure. These comparisons indicate that the wind in 1994 can be described by a model with a wind acceleration parameter ?~0.9, a terminal velocity of 29-33 km s-1, and a mass-loss rate~3�10-9 Msolar yr-1. Modeling of the 3.6 cm radio flux observed in 1997 suggests a more slowly accelerating wind (higher ?) and/or a higher mass-loss rate than inferred from the UV line profiles. These differences may be due to temporal variations in the wind or from limitations in one or both of the models. The discrepancy is currently under investigation. Based on observations with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Carpenter, Kenneth G.; Robinson, Richard D.; Harper, Graham M.; Bennett, Philip D.; Brown, Alexander; Mullan, Dermott J.
A far-infrared survey of bow shocks and detached shells around AGB stars and red supergiants
NASA Astrophysics Data System (ADS)
Aims: Our goal is to study the different morphologies associated to the interaction of the stellar winds of AGB stars and red supergiants with the interstellar medium (ISM) to follow the fate of the circumstellar matter injected into the interstellar medium. Methods: Far-infrared Herschel/PACS images at 70 and 160 ?m of a sample of 78 Galactic evolved stars are used to study the (dust) emission structures developing out of stellar wind-ISM interaction. In addition, two-fluid hydrodynamical simulations of the coupled gas and dust in wind-ISM interactions are used for comparison with the observations. Results: Four distinct classes of wind-ISM interaction (i.e. "fermata", "eyes", "irregular", and "rings") are identified, and basic parameters affecting the morphology are discussed. We detect bow shocks for ~40% of the sample and detached rings for ~20%. The total dust and gas mass inferred from the observed infrared emission is similar to the stellar mass loss over a period of a few thousand years, while in most cases it is less than the total ISM mass potentially swept-up by the wind-ISM interaction. De-projected stand-off distances (R0) - defined as the distance between the central star and the nearest point of the interaction region - of the detected bow shocks ("fermata" and "eyes") are derived from the PACS images and compared to previous results, model predictions, and the simulations. All observed bow shocks have stand-off distances smaller than 1 pc. Observed and theoretical stand-off distances are used together to independently derive the local ISM density. Conclusions: Both theoretical (analytical) models and hydrodynamical simulations give stand-off distances for adopted stellar properties that are in good agreement with the measured de-projected stand-off distance of wind-ISM bow shocks. The possible detection of a bow shock - for the distance-limited sample - appears to be governed by its physical size as set roughly by the stand-off distance. In particular the star's peculiar space velocity and the density of the ISM appear decisive in detecting emission from bow shocks or detached rings. In most cases the derived ISM densities concur with those typical of the warm neutral and ionised gas in the Galaxy, though some cases point towards the presence of cold diffuse clouds. Tentatively, the "eyes" class objects are associated to (visual) binaries, while the "rings" generally do not appear to occur for M-type stars, only for C or S-type objects that have experienced a thermal pulse. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Cox, N. L. J.; Kerschbaum, F.; van Marle, A.-J.; Decin, L.; Ladjal, D.; Mayer, A.; Groenewegen, M. A. T.; van Eck, S.; Royer, P.; Ottensamer, R.; Ueta, T.; Jorissen, A.; Mecina, M.; Meliani, Z.; Luntzer, A.; Blommaert, J. A. D. L.; Posch, Th.; Vandenbussche, B.; Waelkens, C.
The nature of B supergiants: clues from a steep drop in rotation rates at 22 000 K. The possibility of Bi-stability braking
NASA Astrophysics Data System (ADS)
The location of B supergiants in the Hertzsprung-Russell diagram (HRD) represents a long-standing problem in massive star evolution. Here we propose their nature may be revealed utilising their rotational properties, and we highlight a steep drop in massive star rotation rates at an effective temperature of 22 000 K. We discuss two potential explanations for it. On the one hand, the feature might be due to the end of the main sequence, which could potentially constrain the core overshooting parameter. On the other hand, the feature might be the result of enhanced mass loss at the predicted location of the bi-stability jump. We term this effect "bi-stability braking" and discuss its potential consequences for the evolution of massive stars.
Vink, Jorick S.; Brott, I.; Gr�fener, G.; Langer, N.; de Koter, A.; Lennon, D. J.
A grid of non-local thermodynamic equilibrium corrections for magnesium and calcium in late-type giant and supergiant stars: application to Gaia
NASA Astrophysics Data System (ADS)
We investigate non-local thermodynamic equilibrium (NLTE) effects for magnesium and calcium in the atmospheres of late-type giant and supergiant stars. The aim of this paper is to provide a grid of NLTE/LTE equivalent width ratios W/W* of Mg and Ca lines for the following range of stellar parameters: Teff? [3500, 5250] K, log g? [0.5, 2.0] dex and [Fe/H] ? [- 4.0, 0.5] dex. We use realistic model atoms with the best physics available and taking into account the fine structure. The Mg and Ca lines of interest are in optical and near-IR ranges. A special interest concerns the lines in the Gaia spectrograph [Radial Velocity Spectrometer (RVS)] wavelength domain [8470, 8740] �. The NLTE corrections are provided as a function of stellar parameters in an electronic table as well as in a polynomial form for the Gaia/RVS lines.
Merle, T.; Th�venin, F.; Pichon, B.; Bigot, L.
MOST Ultra-High Precision Photometry of the Luminous Blue Supergiant Rigel - Probing the Interior of a Future Type II Supernova
NASA Astrophysics Data System (ADS)
Rigel (B8 Ia; B-V = -0.03; V 0.08- 0.24 mag; 240 +/- 35 pc) is the 7th brightest star in the sky and is the nearest luminous supergiant. From evolutionary tracks, Rigel has an inferred mass of 17 +/- 3 solar masses and an age of 5-10 Myr. Interestingly, Rigel has similar physical properties to the 12th-mag blue supergiant progenitor of SN 1987A: Sanduleak -69� 202a. Rigel (along with its co-asterism Betelgeuse) is likely to be the nearest progenitor of a Type II supernova. Such a nearby explosion would have an apparent magnitude of -10.5 mag (equivalent to the light from the nearly full moon).   We report on initial results of intensive photometry and spectroscopy of Rigel carried out during 2009/10. These observations are part of an international campaign in support of nearly a month of continuous ultra-high precision photometry of Rigel with the Canadian Microsatellite MOST. These observations indicate brightness and radial velocity variations on nearly all time scales - from hours to weeks. These data are being analyzed for periods using various period-search routines. Evidence for a multitude of cyclic/periodic oscillations (with variable amplitudes) appears present in the datasets in addition to stochastic variations. These data will be used to carry out an asteroseismic study of this evolved high mass star. The preliminary results from this program are presented. We acknowledge support for this research from NASA/MOST Grant NNX09AH28G and NSF/RUI Grants AST05-07542 and AST05-07536. We also wish to thank to thank Jaymie Matthews, Rainer Kuschnig and the MOST team for acquiring and reducing the MOST observations.
Guinan, Edward F.; Wasatonic, R.; Engle, S.; Aerts, C.; Morajjevi, E.; Eaton, J.; Fekel, F.; Coughlin, J.; Stewart, H.
IGR J17354-3255 as a candidate intermediate supergiant fast X-ray transient possibly associated with the transient MeV AGL J1734-3310
NASA Astrophysics Data System (ADS)
We present spectral and temporal results from INTEGRAL long-term monitoring of the unidentified X-ray source IGR J17354-3255. We show that it is a weak persistent hard X-ray source spending a major fraction of the time in an out-of-outburst state with an average of 18-60 keV X-ray flux of �1.1 milliCrab, occasionally interspersed with fast X-ray flares (duration from a few hours to a few days) with a dynamic range as high as �200. From archival Swift/X-ray telescope observations, we also show that the dynamic range from non-detection to highest level of measured X-ray activity is >300. Our imager on board the lntegral satellite (IBIS) timing analysis strongly confirms the �8.4 d orbital period previously detected with Swift/burst alert telescope (BAT); in addition we show that the shape of the orbital profile is rather smooth and appears to be dominated by low-level X-ray emission rather than by bright outbursts; the measured degree of outburst recurrence is �25 per cent. The spectral and temporal characteristics of IGR J17354-3255 are highly indicative of a supergiant high-mass X-ray binary (SGXB) nature. However, our inferred dynamic ranges in both soft and hard X-rays are significantly greater than those of classical SGXB systems, but instead are typical of intermediate supergiant fast X-ray transients (SFXTs). Finally, we note for the first time that the observed fast flaring X-ray behaviour of IGR J17354-3255 is very similar to that detected with AGILE from the spatially associated MeV source AGL J1734-3310, suggesting a possible physical link between the two objects.
Sguera, V.; Drave, S. P.; Bird, A. J.; Bazzano, A.; Landi, R.; Ubertini, P.
New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619
NASA Astrophysics Data System (ADS)
XMM-Newton observations of the supergiant fast X-ray transient IGR J17544-2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272 � 0.0004 d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM-Newton observations (each lasting �15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544-2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033 erg s-1 (0.5-10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544-2619 dropped to �4 � 1032 erg s-1 (0.5-10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544-2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544-2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the `quasi-spherical accretion' model provides a good description of the behaviour of IGR J17544-2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model.
Drave, S. P.; Bird, A. J.; Sidoli, L.; Sguera, V.; Bazzano, A.; Hill, A. B.; Goossens, M. E.
Obama Finding Teacher Support Secure, If Tepid: Policy Rifts Complicate Obama-Teacher Dance
ERIC Educational Resources Information Center
Ask Antonio White what he thinks of Race to the Top--President Barack Obama's signature K-12 initiative--and the Florida teacher will tell you the competitive-grant program is a "difficult pill to swallow." Merit pay for teachers based partly on student test scores is "a joke," he says. He's also not a fan of expanding charter schools, or of U.S.�
Klein, Alyson
Calibration of the normal color indices (b-y)0 and absolute stellar magnitudes M(V) for A4-F3-class supergiants on the basis of uvby-beta-photometry data
NASA Astrophysics Data System (ADS)
Calibration relations obtained for the color index (b-y)0 = F (/m1/, r) and absolute magnitudes M(V) = M(V) (beta) for high-luminosity stars are presented. The regions where the calibrations are valid include stars of spectral types ranging from A4 to F3 and luminosity classes from I to II. The calibration relations are used to estimate the distance moduli of 10 supergiants in the LMC.
Dambis, A. K.
... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by military ... there are no guarantees of safety during a chemical emergency, you can take actions to protect yourself. You ...
DISTANCE AND PROPER MOTION MEASUREMENT OF THE RED SUPERGIANT, PZ CAS, IN VERY LONG BASELINE INTERFEROMETRY H{sub 2}O MASER ASTROMETRY
We present the very long baseline interferometry H{sub 2}O maser monitoring observations of the red supergiant, PZ Cas, at 12 epochs from 2006 April to 2008 May. We fitted maser motions to a simple model composed of a common annual parallax and linear motions of the individual masers. The maser motions with the parallax subtracted were well modeled by a combination of a common stellar proper motion and a radial expansion motion of the circumstellar envelope. We obtained an annual parallax of 0.356 {+-} 0.026 mas and a stellar proper motion of {mu}{sub {alpha}}{sup *} cos {delta} = -3.7 {+-} 0.2 and {mu}{sup *}{sub {delta}}=-2.0{+-}0.3 mas yr{sup -1} eastward and northward, respectively. The annual parallax corresponds to a trigonometric parallax of 2.81{sup +0.22}{sub -0.19} kpc. By rescaling the luminosity of PZ Cas in any previous studies using our trigonometric parallax, we estimated the location of PZ Cas on a Hertzsprung-Russell diagram and found that it approaches a theoretically evolutionary track around an initial mass of {approx}25 M{sub Sun }. The sky position and the distance to PZ Cas are consistent with the OB association, Cas OB5, which is located in a molecular gas super shell. The proper motion of PZ Cas is close to that of the OB stars and other red supergiants in Cas OB5 measured by the Hipparcos satellite. We derived the peculiar motion of PZ Cas of U{sub s} = 22.8 {+-} 1.5, V{sub s} = 7.1 {+-} 4.4, and W{sub s} = -5.7 {+-} 4.4 km s{sup -1}. This peculiar motion has rather a large U{sub s} component, unlike those of near high-mass star-forming regions with negatively large V{sub s} motions. The uniform proper motions of the Cas OB5 member stars suggest random motions of giant molecular clouds moving into local potential minima in a time-dependent spiral arm, rather than a velocity field caused by the spiral arm density wave.
Kusuno, K.; Asaki, Y. [Department of Space and Astronautical Science, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), 3-1-1 Yoshinodai, Chuou-Ku, Sagamihara, Kanagawa 252-5210 (Japan); Imai, H. [Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Oyama, T., E-mail: email@example.com, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com [Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
Dust Production Factories in the Early Universe: Formation of Carbon Grains in Red-supergiant Winds of Very Massive Population III Stars
NASA Astrophysics Data System (ADS)
We investigate the formation of dust in a stellar wind during the red-supergiant (RSG) phase of a very massive Population III star with a zero-age main sequence mass of 500 M ?. We show that, in a carbon-rich wind with a constant velocity, carbon grains can form with a lognormal-like size distribution, and that all of the carbon available for dust formation finally condenses into dust for wide ranges of the mass-loss rate ((0.1-3) � 10-3 M ? yr-1) and wind velocity (1-100 km s-1). We also find that the acceleration of the wind, driven by newly formed dust, suppresses the grain growth but still allows more than half of the gas-phase carbon to finally be locked up in dust grains. These results indicate that, at most, 1.7 M ? of carbon grains can form during the RSG phase of 500 M ? Population III stars. Such a high dust yield could place very massive primordial stars as important sources of dust at the very early epoch of the universe if the initial mass function of Population III stars was top-heavy. We also briefly discuss a new formation scenario of carbon-rich ultra-metal-poor stars, considering feedback from very massive Population III stars.
Nozawa, Takaya; Yoon, Sung-Chul; Maeda, Keiichi; Kozasa, Takashi; Nomoto, Ken'ichi; Langer, Norbert
The Contribution of Thermally-Pulsing Asymptotic Giant Branch and Red Supergiant Stars to the 1--24 Micron Flux of the Magellanic Clouds
NASA Astrophysics Data System (ADS)
Dust enshrouded Asymptotic Giant Branch (AGB) stars and their more massive counterparts, Red Supergiants (RSG), are among the brightest near- and mid-infrared (IR) sources in a galaxy. These stars constitute a tiny fraction of a galaxy's stellar mass, and yet can account for large fractions of the integrated near and mid-IR flux. Underestimating the AGB and RSG contributions to the IR luminosity can result in severely over-estimating a galaxy's stellar mass as well as inflation of the star formation rate estimated from the 8-micron rest-frame flux. Despite their importance, the AGB and RSG flux contribution has only been measured in a handful of galaxies at a handful of wavelengths. Recent Spitzer Space Telescope observations of the Small and Large Magellanic Clouds offer the first opportunity to quantify the IR contribution of the complete population of Thermally-pulsing (TP-)AGB stars and RSG stars to the total integrated IR light from 1 -24 microns. We find that the TP-AGB + RSG flux contribution peaks at 30% at 3--5 microns in the SMC and 25% in the LMC. Even at 8 microns these stars account for 20% of the SMC flux, with nearly half of that flux coming from a handful (3% of the AGB population) of extreme carbon stars. In the LMC, where PAH emission in the interstellar medium is stronger, the 8 micron TP-AGB + RSG flux contribution is much smaller, 4%.
Boyer, Martha L.; Melbourne, J.
Spitzer-IRS Spectroscopic Studies of the Properties of Dust from Oxygen-Rich Asymptotic Giant Branch and Red Supergiant Stars
NASA Astrophysics Data System (ADS)
We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of Oxygen-rich (O-rich) asymptotic giant branch (AGB) and red supergiant (RSG) stars. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper) and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.
Sargent, Benjamin A.; Speck, A.; Volk, K.; Kemper, C.; Reach, W. T.; Lagadec, E.; Bernard, J.; McDonald, I.; Meixner, M.; Srinivasan, S.
Chemical agents are poisonous vapors, aerosols, liquids and solids that have toxic effects on people, animals or plants. They ... hazard to people and the environment. Some chemical agents may be odorless and tasteless. They can have ...
NSDL National Science Digital Library
This lesson provides an introduction to the occurrence and possible risks of household chemical products. Topics include some basic chemistry (how elements combine to form compounds), how chemicals are classified, and the idea of natural, as opposed to synthetic, chemicals. The lesson includes an activity in which students take an inventory of chemical products in their homes and research the possible hazards of some of them using an online resource developed by the National Institutes of Health (NIH).
Fox, Chris
Chemical Biology\\/ Chemical Genetics\\/ Chemical Genomics: Importance of Chemical Library
A new field of science, chemical biology\\/ chemical genetics\\/ chemical genomics (cb\\/cg\\/cg) has emerged since the late 1990's, especially in the United States. The NIH Roadmap agenda, Molecular Libraries Screening Center Network (MLSCN), became a drive force to push cb\\/cg\\/cg forward. Cb\\/cg\\/cg studies consist of three methodologies, chemical libraries with small molecules, high-throughput screenings, and computational databases. In this review,
Fumihiko Kugawa; Masaru Watanabe; Fuyuhiko Tamanoi
NASA Technical Reports Server (NTRS)
A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance.
Rauh, R. David (Inventor)
Metal-poor massive stars typically end their lives as blue supergiants (BSGs). Gamma-ray bursts (GRBs) from such progenitors could have an ultra-long duration of relativistic jets. For example, Population III (Pop III) GRBs at z {approx} 10-20 might be observable as X-ray-rich events with a typical duration of T{sub 90} {approx} 10{sup 4}(1 + z) s. The recent GRB111209A at z = 0.677 has an ultra-long duration of T{sub 90} {approx} 2.5 Multiplication-Sign 10{sup 4} s and it has been suggested that its progenitor might have been a metal-poor BSG in the local universe. Here, we suggest that luminous UV/optical/infrared emission is associated with this new class of GRBs from metal-poor BSGs. Before the jet head breaks out of the progenitor envelope, the energy injected by the jet is stored in a hot plasma cocoon, which finally emerges and expands as a baryon-loaded fireball. We show that the photospheric emissions from the cocoon fireball could be intrinsically very bright (L{sub peak} {approx} 10{sup 42}-10{sup 44} erg s{sup -1}) in UV/optical bands ({epsilon}{sub peak} {approx} 10 eV) with a typical duration of {approx}100 days in the rest frame. Such cocoon emissions from Pop III GRBs might be detectable in infrared bands at {approx}years after Pop III GRBs at up to z {approx} 15 by upcoming facilities such as the James Webb Space Telescope. We also suggest that GRB111209A might have been rebrightening in UV/optical bands up to an AB magnitude of {approx}< 26. The cocoon emission from local metal-poor BSGs might have been observed previously as luminous supernovae without GRBs since they can be seen from the off-axis direction of the jet.
Kashiyama, Kazumi; Yajima, Hidenobu [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Nakauchi, Daisuke; Nakamura, Takashi [Department of Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan); Suwa, Yudai, E-mail: firstname.lastname@example.com [Yukawa Institute for Theoretical Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan)
Warm water vapor envelope in the supergiants ? Ori and ? Her and its effects on the apparent size from the near-infrared to the mid-infrared
NASA Astrophysics Data System (ADS)
We present a possible interpretation for the increase of the angular diameter of the supergiants ? Ori (M 1-2 Ia-Ibe) and ? Her (M 5 Ib-II) from the K band to the 11 ?m region and the high-resolution 11 ?m spectra without any salient spectral features revealed by Weiner et al. (\\cite{weiner03a}). The angular diameters as well as the high-resolution spectra of ? Ori and ? Her obtained in the 11 ?m region can be reproduced by a warm water vapor envelope, whose presence in ? Ori was revealed by Tsuji (\\cite{tsuji00a}) based on the reanalysis of the near-infrared data obtained with the Stratoscope II. While prominent absorption due to H2O can be expected from such a dense, warm water vapor envelope, the absorption lines can be filled in by emission from the extended part of the envelope. This effect leads to a significant weakening of the H2O lines in the 11 ?m region, and makes the observed spectra appear to be rather featureless and continuum-like. However, the emission due to H2O lines from the extended envelope leads to an increase of the apparent size in this spectral region. The observed angular diameter and the high resolution spectra of ? Ori and ? Her in the 11 ?m region can be best interpreted by the water vapor envelope extending to 1.4-1.5 R*, with a temperature of �2000 K and a column density of H2O of the order of 1020 cm-2.
Ohnaka, K.
The Contribution of Thermally-Pulsing Asymptotic Giant Branch and Red Supergiant Starts to the Luminosities of the Magellanic Clouds at 1-24 micrometers
NASA Technical Reports Server (NTRS)
We present the near-through mid-infrared flux contribution of thermally-pulsing asymptotic giant branch (TP-AGB) and massive red supergiant (RSG) stars to the luminosities of the Large and Small Magellanic Clouds (LMC and SMC, respectively). Combined, the peak contribution from these cool evolved stars occurs at approx 3 - 4 micron, where they produce 32% of the SMC light, and 25% of the LMC flux. The TP-AGB star contribution also peaks at approx 3 - 4 micron and amounts to 21% in both galaxies. The contribution from RSG stars peaks at shorter wavelengths, 2.2 micron, where they provide 11% of the SMC flux, and 7% for the LMC. Both TP-AGB and RSG stars are short lived, and thus potentially impose a large stochastic scatter on the near-IR derived mass-to-light (M/L) ratios of galaxies at rest-frame 1 - 4 micron. To minimize their impact on stellar mass estimates, one can use the M/L ratio at shorter wavelengths (e.g., at 0.8 - 1 micron). At longer wavelengths (much > 8 micron), emission from dust in the interstellar medium dominates the flux. In the LMC, which shows strong polycyclic aromatic hydrocarbon (PAH) emission at 8 micron, TP-AGB and RSG contribute less than 4% of the 8 micron flux. However, 19% of the SMC 8 micron flux is from evolved stars, nearly half of which is produced by the rarest, dustiest, carbon-rich TP-AGB stars. Thus, star formation rates of galaxies, based on an 8 micron flux (e.g., observed-frame 24 micron at z = 2), may be biased modestly high, especially for galaxies with little PAH emission.
Melbourne, J.; Boyer, Martha L.
NSDL National Science Digital Library
What do chemical engineers actually do? This is the introductory page for a set of materials about chemical engineering as a career. Here the job of a chemical engineer is defined and described. Chemical engineers often work with industrial manufacturing processes that involve a mix of chemistry and engineering. In the rest of the resource, students can examine a specialized job title associated with chemical engineering: process engineer. Students can view a five-minute video clip of the process engineer as he works in a fertilizer plant making ammonia and urea. Students follow the engineer around the plant as he checks pressure in chemical lines. Students get a glimpse of the inside of a furnace during the chemical-making process. Copyright 2005 Eisenhower National Clearinghouse
Project, Iowa P.
NSDL National Science Digital Library
Electrons are key to forming the two broad categories of chemical bonds: covalent and ionic. Atoms, which have a nucleus surrounded by electrons, are represented in several different ways. In the Chemical Bonds activity, students explore the different kinds of chemical bonds that can form, ranging from non-polar covalent to ionic. In the model depicted above students adjust the electronegativity of two atoms and see the effect it has on electron distribution and bond type.
Consortium, The C.
NASA Astrophysics Data System (ADS)
Measurements of the chemical compositions of materials and the levels of certain substances in them are vital when assessing and improving public health, safety and the environment, are necessary to ensure trade equity, and are required when monitoring and improving industrial products and services. Chemical measurements play a crucial role in most areas of the economy, including healthcare, food and nutrition, agriculture, environmental technologies, chemicals and materials, instrumentation, electronics, forensics, energy, and transportation.
May, Willie; Cavanagh, Richard; Turk, Gregory; Winchester, Michael; Travis, John; Smith, Melody; Derose, Paul; Choquette, Steven; Kramer, Gary; Sieber, John; Greenberg, Robert; Lindstrom, Richard; Lamaze, George; Zeisler, Rolf; Schantz, Michele; Sander, Lane; Phinney, Karen; Welch, Michael; Vetter, Thomas; Pratt, Kenneth; Scott, John; Small, John; Wight, Scott; Stranick, Stephan
Chemical agents and chemical terrorism.
Chemical terrorism is a new threat to the security of mankind, which scale essentially exceeds the impact of use of the most modem firearms. At present time all over the world threats from different radical elements to use radioactive materials, potent poisonous substances and pathogenic microorganisms for terrorist purposes became more frequent. High-toxic chemical substances can fall in terrorist hands through wide range of sources. Potentially misused types of chemical compounds are discussed in this article. PMID:15141987
Patocka, J; Fusek, J
A chemical preconcentrator is disclosed with applications to chemical sensing and analysis. The preconcentrator can be formed by depositing a resistive heating element (e.g. platinum) over a membrane (e.g. silicon nitride) suspended above a substrate. A coating of a sorptive material (e.g. a microporous hydrophobic sol-gel coating or a polymer coating) is formed on the suspended membrane proximate to the heating element to selective sorb one or more chemical species of interest over a time period, thereby concentrating the chemical species in the sorptive material. Upon heating the sorptive material with the resistive heating element, the sorbed chemical species are released for detection and analysis in a relatively high concentration and over a relatively short time period. The sorptive material can be made to selectively sorb particular chemical species of interest while not substantially sorbing other chemical species not of interest. The present invention has applications for use in forming high-sensitivity, rapid-response miniaturized chemical analysis systems (e.g. a "chem lab on a chip").
Manginell, Ronald P. (Albuquerque, NM); Frye-Mason, Gregory C. (Cedar Crest, NM)
Attachment III Chemical Quick Reference Chart for Minors Chemical Name Select Carcinogen Reproductive Toxin LD50 < 50 mg/kg (oral rat) LD50 < 200 mg/kg for 24 hours or less (dermal rabbit) LC50 < 200 ppm or 2 mg/L for one hour (inhalation rat)
... to Ask Before a Cosmetic Procedure Chemical Peeling (AAD pamphlet) The Lunchtime Peel: What It Can Do ... et al , editors. Fitzpatrick�s Dermatology in General Medicine . 7 th edition. United States of America, McGraw Hill ...
ERIC Educational Resources Information Center
Discusses the health hazards resulting from chemical additions of many common products such as cough syrups, food dyes, and cosmetics. Steps being taken to protect consumers from these health hazards are included. (MDR)
Johnson, Anita
... a brow lift, eye lift or soft-tissue filler injection. Mild scarring and certain types of acne also can be treated with chemical peels. In addition, pigmentation of the skin in the form of sun spots, age spots, ...
MedlinePLUS Videos and Cool Tools
... 2014 Related MedlinePlus Pages Environmental Health Hormones Transcript Phthalates are a group of chemicals used to make ... the ban has helped lower exposure to some phthalates, while opening the door to others. Researchers looked ...
GHRS Observations of Cool, Low-Gravity Stars. 5; The Outer Atmosphere and Wind of the Nearby K Supergiant Lambda Velorum
NASA Technical Reports Server (NTRS)
UV spectra of lambda Velorum taken with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope are used to probe the structure of the outer atmospheric layers and wind and to estimate the mass-loss rate from this K5 lb-II supergiant. VLA radio observations at lambda = 3.6 cm are used to obtain an independent check on the wind velocity and mass-loss rate inferred from the UV observations, Parameters of the chromospheric structure are estimated from measurements of UV line widths, positions, and fluxes and from the UV continuum flux distribution. The ratios of optically thin C II] emission lines indicate a mean chromospheric electron density of log N(sub e) approximately equal 8.9 +/- 0.2 /cc. The profiles of these lines indicate a chromospheric turbulence (v(sub 0) approximately equal 25-36 km/s), which greatly exceeds that seen in either the photosphere or wind. The centroids of optically thin emission lines of Fe II and of the emission wings of self-reversed Fe II lines indicate that they are formed in plasma approximately at rest with respect to the photosphere of the star. This suggests that the acceleration of the wind occurs above the chromospheric regions in which these emission line photons are created. The UV continuum detected by the GHRS clearly traces the mean flux-formation temperature as it increases with height in the chromosphere from a well-defined temperature minimum of 3200 K up to about 4600 K. Emission seen in lines of C III] and Si III] provides evidence of material at higher than chromospheric temperatures in the outer atmosphere of this noncoronal star. The photon-scattering wind produces self-reversals in the strong chromospheric emission lines, which allow us to probe the velocity field of the wind. The velocities to which these self-absorptions extend increase with intrinsic line strength, and thus height in the wind, and therefore directly map the wind acceleration. The width and shape of these self-absorptions reflect a wind turbulence of approximately equal 9-21 km/s. We further characterize the wind by comparing the observations with synthetic profiles generated with the Lamers et al. Sobolev with Exact Integration (SEI) radiative transfer code, assuming simple models of the outer atmospheric structure. These comparisons indicate that the wind in 1994 can be described by a model with a wind acceleration parameter beta approximately 0.9, a terminal velocity of 29-33 km/s, and a mass-loss rate approximately 3 x 10(exp -9) solar M/yr. Modeling of the 3.6 cm radio flux observed in 1997 suggests a more slowly accelerating wind (higher beta) and/or a higher mass-loss rate than inferred from the UV line profiles. These differences may be due to temporal variations in the wind or from limitations in one or both of the models. The discrepancy is currently under investigation.
Carpenter, Kenneth G.; Robinson, Richard D.; Harper, Graham M.; Bennett, Philip D.; Brown, Alexander; Mullan, Dermott J.
ERIC Educational Resources Information Center
An open-access, Web-based mnemonic game is described whereby introductory chemistry knowledge is tested using mahjong solitaire game play. Several tile sets and board layouts are included that are themed upon different chemical topics. Introductory tile sets can be selected that prompt the player to match element names to symbols and metric�
Cossairt, Travis J.; Grubbs, W. Tandy
NSDL National Science Digital Library
Students are introduced to chemical engineering and learn about its many different applications. They are provided with a basic introduction to matter and its different properties and states. An associated hands-on activity gives students a chance to test their knowledge of the states of matter and how to make observations using their five senses: touch, smell, sound, sight and taste.
Integrated Teaching And Learning Program
ERIC Educational Resources Information Center
This paper presents an approach to chemistry and nutrition that focuses on food items that people consider delicious. Information is organized according to three categories of food chemicals that provide energy to the human body: (1) fats and oils; (2) carbohydrates; and (3) proteins. Minerals, vitamins, and additives are also discussed along with�
Barry, Dana M.
Leaf-cutting ants are well known for their highly complex social organization, which provides them with a strong defense against parasites invading their colonies. Besides this attribute, these insects have morphological, physiological and structural characteristics further reinforcing the defense of their colonies. With the discovery of symbiotic bacteria present on the integument of leaf-cutting ants, a new line of defense was proposed and considered to be specific for the control of a specialized fungal parasite of the ants� fungus gardens (Escovopsis). However, recent studies have questioned the specificity of the integumental bacteria, as they were also found to inhibit a range of fungi, including entomopathogens. The microbiota associated with the leaf-cutting ant gardens has also been proposed as another level of chemical defense, protecting the garden from parasite invasion. Here we review the chemical defense weaponry deployed by leaf-cutting ants against parasites of their fungus gardens and of the ants themselves.
Samuels, Richard Ian; Mattoso, Thalles Cardoso; Moreira, Denise D.O.
NSDL National Science Digital Library
This site contains complete notes in a PowerPoint-like presentation for a chemical separations course. It covers a wide variety of topics, including distillation, extraction, gas chromatography, liquid chromatograpy, chromatography theory, instrumentation, electrophoresis, field flow fractionation, and affinity chromatography. It covers these topics thoroughly using a clear, consistent, and simple presentation style. Links to major topics like GC, LC, and electrophoresis provide specific information about the theory, instrumentation, and practice related to these techniques. The site also contains many annimations illustrating important separation processes.
The purpose of chemical spectroscopy with neutrons is to utilize the dependence of neutron scattering cross-sections on isotope and on momentum transfer (which probes the spatial extent of the excitation) to understand fundamental and applied aspects of the dynamics of molecules and fluids. Chemical spectroscopy is divided into three energy ranges: vibrational spectroscopy, 25-500 MeV, for which much of the work is done on Be-filter analyzer instruments; low energy spectroscopy, less than 25 MeV; and high resolution spectroscopy, less than 1 MeV, which typically is performed on backscattering spectrometers. Representative examples of measurements of the Q-depenence of vibrational spectra, higher energy resolution as well as extension of the Q-range to lower values at high energy transfers, and provisions of higher sensitivities in vibrational spectroscopy are discussed. High resolution, high sensitivity, and polarization analysis studies in low energy spectroscopy are discussed. Applications of very high resolution spectroscopy are also discussed. (LEW)
Eckert, J.; Brun, T.O.; Dianoux, A.J.; Howard, J.; Rush, J.J.; White, J.W.
NASA Technical Reports Server (NTRS)
As a preliminary study on the effects of chemical aging of polymer materials MERL and TRI have examined two polymeric materials that are typically used for offshore umbilical applications. These two materials were Tefzel, a copolymer of ethylene and tetrafluoroethylene, and Coflon, polyvinylidene fluoride. The Coflon specimens were cut from pipe sections and exposed to H2S at various temperatures and pressures. One of these specimens was tested for methane permeation, and another for H2S permeation. The Tefzel specimens were cut from .05 mm sheet stock material and were exposed to methanol at elevated temperature and pressure. One of these specimens was exposed to methanol permeation for 2 days at 100 C and 2500 psi. An additional specimen was exposed to liquid methanol for 3 days at 150 C and 15 Bar. Virgin specimens of each material were similarly prepared and tested.
Bulluck, J. W.; Rushing, R. A.
Chemical Ecology: Chemical Communication in Nature.
ERIC Educational Resources Information Center
Substances that deliver chemical messages between same/different species are called semiochemicals. Surveyed are three types of semiochemicals (pheromones, allomones, and kairomones), types of organisms involved, and specific chemicals used to carry the various kinds of messages. (JN)
Wood, William F.
Modern Chemical Technology, Guidebook for Chemical Technicians.
ERIC Educational Resources Information Center
This volume is a part of the ACS "Modern Chemical Technology" (ChemTeC) curriculum that is developed for chemical technicians. It is intended as a handbook that will be used throughout the instruction. Safety is stressed in eight of the ten chapters under the headings: safety in the chemical laboratory, personal protective equipment, fire safety�
Pecsok, Robert L.; Chapman, Kenneth
National Technical Information Service (NTIS)
The course, which is presented in cooperation with the U.S. Environmental Protection Agency's (EPA) Office of Chemical Emergency Preparedness Planning, introduces safety auditing for highly hazardous chemicals. The course covers basic chemical systems and...
Nature's chemicals and synthetic chemicals: comparative toxicology.
The toxicology of synthetic chemicals is compared to that of natural chemicals, which represent the vast bulk of the chemicals to which humans are exposed. It is argued that animals have a broad array of inducible general defenses to combat the changing array of toxic chemicals in plant food (nature's pesticides) and that these defenses are effective against both natural and synthetic toxins. Synthetic toxins such as dioxin are compared to natural chemicals, such as indole carbinol (in broccoli) and ethanol. Trade-offs between synthetic and natural pesticides are discussed. The finding that in high-dose tests, a high proportion of both natural and synthetic chemicals are carcinogens, mutagens, teratogens, and clastogens (30-50% for each group) undermines current regulatory efforts to protect public health from synthetic chemicals based on these tests.
Ames, B N; Profet, M; Gold, L S
... that cause nausea and vomiting Hazardous chemicals by name (A-Z list) If you know the name of a chemical but aren�t sure what ... in, you can look for the chemical by name on the A�Z List of Chemical Agents . ...
Chemical Composition of Two H II Regions in NGC 6822 Based on VLT Spectroscopy
NASA Astrophysics Data System (ADS)
We present long slit spectrophotometry of regions V and X of the local group irregular galaxy NGC 6822. The data consist of VLT FORS observations in the 3450 to 7400 � range. We have obtained electron temperatures and densities using different line intensity ratios. We have derived the H, He, C, and O abundances based on recombination lines; the abundance ratios among these elements are almost independent of the temperature structure of the nebulae. We have also determined the N, O, Ne, S, Cl, and Ar abundances based on collisionally excited lines; the ratios of these abundances relative to that of H depend strongly on the temperature structure of the nebulae. We compare the chemical composition of NGC 6822 V with those of the Sun, the Orion nebula, NGC 346 in the SMC, and 30 Doradus in the LMC. The O/H value derived from recombination lines for NGC 6822 V is in good agreement with the value derived by Venn et al. (2001) from A type supergiants in NGC 6822. MP received partial support from DGAPA UNAM (grant IN 114601). AP received partial support from DGAPA UNAM (grant IN 118405). MTR received partial support from FONDAP(15010003), a Guggenheim Fellowship and Fondecyt(1010404).
Peimbert, M.; Peimbert, A.; Ruiz, M. T.
NASA Technical Reports Server (NTRS)
Ionospheric plasma density irregularities can be produced by chemical releases into the upper atmosphere. F-region plasma modification occurs by: (1) chemically enhancing the electron number density; (2) chemically reducing the electron population; or (3) physically convecting the plasma from one region to another. The three processes (production, loss, and transport) determine the effectiveness of ionospheric chemical releases in subtle and surprising ways. Initially, a chemical release produces a localized change in plasma density. Subsequent processes, however, can lead to enhanced transport in chemically modified regions. Ionospheric modifications by chemical releases excites artificial enhancements in airglow intensities by exothermic chemical reactions between the newly created plasma species. Numerical models were developed to describe the creation and evolution of large scale density irregularities and airglow clouds generated by artificial means. Experimental data compares favorably with theses models. It was found that chemical releases produce transient, large amplitude perturbations in electron density which can evolve into fine scale irregularities via nonlinear transport properties.
Bernhardt, Paul A.; Scales, W. A.
Chemical Reference Literature.
National Technical Information Service (NTIS)
An innovative and effective laboratory experiment of chemical reference literature is reported. The objectives of the experiment are to acquaint the first term student of college chemistry with the vast source of chemical literature that is available to h...
S. M. Young
NSDL National Science Digital Library
The phenomena are physical changes, including the crushing of a can, melting of ice, and melting of sugar, and chemical changes, including and the rusting of iron and burning of sugar. This analysis will address the chemical change component.
National Technical Information Service (NTIS)
On April 29, 1997, the Convention on the Prohibition of the Development, Production, Stockpiling, and Use of Chemical Weapons and on Their Destruction, known as the Chemical Weapons Convention (CWC), entered into force. At that time, the United States and...
Advanced Chemical Engineering Research.
National Technical Information Service (NTIS)
Ten advanced chemical engineering research projects were executed at the US Army Natick RDE Center over a three month period by students of the David H. Koch School of Chemical Engineering Practice, administered by the Massachusetts Institute of Technolog...
T. A. Hatton
Alternatives in Chemical Education
ERIC Educational Resources Information Center
Summarizes the educational objectives and strategies of the Chemical Technician Curriculum Project (Chem TeC), which has the primary objective of preparing a set of texts specifically for training chemical technicians. (PR)
Pecsok, Robert L.
The Chemical Equilibrium Problem.
National Technical Information Service (NTIS)
It has long been known that the problem of determining the equilibrium composition of a solution of chemically reacting species could be formulated as a constrained minimum problem. Previous methods for solving the chemical equilibrium problem in this for...
J. H. Bigelow
Personal Chemical Exposure informatics
Chemical Exposure science is the study of human contact with chemicals (from manufacturing facilities, everyday products, waste) occurring in their environments and advances knowledge of the mechanisms and dynamics of events that cause or prevent adverse health outcomes. (adapted...
National Technical Information Service (NTIS)
A study of the economics of producing chemicals from wood waste was carried out for the Forest Products Laboratory. Results included: (1) outlining chemical processes based on known technology for producing methanol, ethanol, formaldehyde, furfural, and p...
A. E. Hokanson V. B. Diebold D. W. Bennett R. P. Klier S. A. Stein
NSDL National Science Digital Library
Overview of physical and chemical changes with practice activities and a quiz. Worksheet - Physical Chemical Change Worksheet After viewing the worksheet, copy and paste it into a new blank Google Document - MyDSD Google Login Title your Document "Chemical and Physical Change". Make sure to include your name and period in the body of the doc. The answers in your document should be a different color or font. Examples of Chemical Changes Changes info page More Examples After completing the rest ...
Wood, Mr.
Computing Equilibrium Chemical Compositions
NASA Technical Reports Server (NTRS)
Chemical Equilibrium With Transport Properties, 1993 (CET93) computer program provides data on chemical-equilibrium compositions. Aids calculation of thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93/PC is version of CET93 specifically designed to run within 640K memory limit of MS-DOS operating system. CET93/PC written in FORTRAN.
Mcbride, Bonnie J.; Gordon, Sanford
The elusive chemical potential
NSDL National Science Digital Library
The author offers some qualitative understanding of the chemical potential, a topic that students invariably find difficult. Three "meanings" for the chemical potential are stated and then supported by analytical development. Two substantial applications � depression of the melting point and batteries � illustrate the chemical potential in action. The origin of the term "chemical potential" has its surprises, and a sketch of the history is given.variable particle number.
Baierlein, Ralph
NSDL National Science Digital Library
This database provides information on thousands of chemical compounds, including synthesis references and physical properties. The database is searchable by keyword and browseable by journal title. For each compound, the information includes molecular formula and weight, Chemical Abstracts Service (CAS) numbers, International Chemical Identifier (InChIKey), and Simplified Molecular Input Line Entry System (SMILES) notation. There is also information on synonyms, physical properties (boiling and melting points, density), an illustration of chemical structure, spectral data, and links to additional data.
Adaptability in Chemical Engineering.
National Technical Information Service (NTIS)
The adaptability issue for chemical engineering (the ability of chemical engineers to be retrained to work in other fields and for those from other fields to be retrained for work in chemical engineering) will be discussed and illustrated in terms of (1) ...
J. S. Watson
Chemical Exposure: An Overview
Agricultural chemicals comprise thousands of formulations, including petroleum products, pesticides, growth regulators, buffers, nutrients and fertilizers, and veterinary medications. These chemicals may be used as solids in granular, powder, pellet, or block form; liquids in mists and sprays; or in gaseous forms as fumigants or fuels. Application of chemicals to crops may be by sprays of liquids from aircraft or
Chemical Education in Bulgaria
The sociopolitical changes in Eastern Europe of the 1990s and the ongoing globalization of the chemical industry and chemical education prompted this analysis of the current status of chemical education in Bulgaria, which is not very different from the educational practices in the rest of Europe. The level of chemistry knowledge expected from all high-school graduates in Bulgaria is roughly
Vladimir N. Garkov
This report, which summarizes the use of agricultural chemicals is issued by the National Agricultural Statistics Service (NASS) as part of its series on Agricultural Chemical Usage. Other publications in the series present statistics for on-farm agricultural chemical usage for f...
Toxicology and Chemical Safety.
ERIC Educational Resources Information Center
Topics addressed in this discussion of toxicology and chemical safety include routes of exposure, dose/response relationships, action of toxic substances, and effects of exposure to chemicals. Specific examples are used to illustrate the principles discussed. Suggests prudence in handling any chemicals, whether or not toxicity is known. (JN)
Hall, Stephen K.
Chemicals for worldwide aquaculture
Regulations and therapeutants or other safe chemicals that are approved or acceptable for use in the aquaculture industry in the US, Canada, Europe and Japan are presented, discussing also compounds that are unacceptable for aquaculture. Chemical use practices that could affect public health are considered and details given regarding efforts to increase the number of registered and acceptable chemicals.
Schnick, R. A.
Establishing Chemical Technology Programs.
ERIC Educational Resources Information Center
In light of the increasing demand for well-prepared chemical technicians, this paper provides suggestions for two-year colleges interested in initiating or upgrading a chemical technology program. Introductory comments indicate that, from the industry standpoint, chemical technicians are invaluable, but inadequate in numbers and often unprepared.�
Hajian, Harry G.
Practical Chemical Sensors from Chemically Derived Graphene
We report the development of useful chemical sensors from chemically converted graphene dispersions using spin coating to create single-layer films on interdigitated electrode arrays. Dispersions of graphene in anhydrous hydrazine are formed from graphite oxide. Preliminary results are presented on the detection of NO2,NH3, and 2,4-dinitrotoluene using this simple and scalable fabrication method for practical devices. Currentversusvoltage curves are linear
Jesse D. Fowler; Matthew J. Allen; Vincent C. Tung; Yang Yang; Richard B. Kaner; Bruce H. Weiller
NSDL National Science Digital Library
This lesson for Grades 6-8 combines a short video with three experiments to observe and record chemical changes. The experiments use common household materials to demonstrate chemical reaction -- a change that leads to a transformation of one substance into another substance. In the 3rd experiment, there are two chemical reactions happening at the same time. Through careful observation, learners see that the 3rd reaction represents a "chemical clock", because the time it takes the chemicals to react happens very predictably, like a regular clock. Talking Science is part of National Public Radio's Science Friday initiative.
NSDL National Science Digital Library
The National Oceanic and Atmospheric Administration's (NOAA) Office of Response and Restoration has created the Chemical Reactivity Worksheet to help teachers, students, and the general public learn about the chemical reactivity of thousands of common hazardous chemicals. After downloading a free program, visitors will find that the datasheets contain information about the hazards of a number of chemicals, along with information on whether a chemical reacts with air, water, or other materials. Visitors can create their own custom chemical datasheets or virtually "mix" chemicals to find out what dangers might arise from accidental mixing. The site is rounded out by an excellent FAQ section, along with information about the technical specifications of the program and a development history.
Idaho Chemical Processing Plant safety document ICPP hazardous chemical evaluation.
National Technical Information Service (NTIS)
This report presents the results of a hazardous chemical evaluation performed for the Idaho Chemical Processing Plant (ICPP). ICPP tracks chemicals on a computerized database, Haz Track, that contains roughly 2000 individual chemicals. The database contai...
B. J. Harwood
The Cepheid + Supergiant Eclipsing System BM Cas
BM Cas is an eclipsing binary for which Fernie has recently found magnitude variations from the secondary best explained by Cepheid pulsation. Because a Cepheid in an eclipsing binary provides the possibility of determining both its mass and radius, extensive photometric and spectroscopic observations are being carried out. In addition, the system is the shortest period eclipsing system containing a
Nancy Remage Evans
Red supergiants around Stephenson 2 (Negueruela+, 2012)
NASA Astrophysics Data System (ADS)
Observations were carried out with the AutoFib2+WYFFOS (AF2) multi-object, wide-field, fibre spectrograph mounted on the Prime Focus of the 4.2m William Herschel Telescope (WHT), in La Palma, Spain. The observations were taken on the nights of 2009, June 5th (in service mode) and June 6th-7th (in visitor mode). (2 data files).
Negueruela, I.; Marco, A.; Gonzalez-Fernandez, C.; Jimenez-Esteban, F.; Clark, J. S.; Garcia, M.; Solano, E.
Red Supergiants in the Local Group
NASA Astrophysics Data System (ADS)
Galaxies in the Local Group span a factor of 15 in metallicity, ranging from the super-solar M 31 to the Wolf-Lundmark-Melotte (WLM) galaxy, which is the lowest-metallicity (0.1 Z?) Local Group galaxy currently forming stars. Studies of massive star populations across this broad range of environments have revealed important metal-licity-dependent evolutionary trends, allowing us to test the accuracy of stellar evolutionary tracks at these metallicities for the first time. The RSG population is particularly valuable as a key mass-losing phase of moderately massive stars and a source of core-collapse supernova progenitors. By reviewing recent work on the RSG populations in the Local Group, we are able to quantify limits on these stars' effective temperatures and masses and probe the relationship between RSG mass loss behaviors and host environments. Extragalactic surveys of RSGs have also revealed several unusual RSGs that display signs of unusual spectral variability and dust production, traits that may potentially also correlate with the stars' host environments. I will present some of the latest work that has advanced our understanding of RSGs in the Local Group, and consider the many new questions posed by our ever-evolving picture of these stars.
Levesque, E. M.
Hazardous chemicals desk reference
This book supplies instant-access data on nearly 4,700 of the most dangerous chemicals and compounds used in the workplace. It alerts readers to potential short- and long-term hazards by providing for each chemical a 1 to 3 hazard rating ... CAS, NIOSH, and DOT numbers ... concise descriptions of physical properties ... synonyms ... and current standards for exposure limits. A Toxic and Hazard Review (THR) paragraph for each chemical indicates whether the chemical is poisonous, an irritant, corrosive, explosive, or carcinogenic. Special chapters on safety provide clear guidance on the safe handling and storage of chemicals, the use of respirators, the selection of chemical protective clothing, fire protection, and first aid in the workplace.
Sax, N.I.; Lewis, R.J. Sr.
Multivariate Quantitative Chemical Analysis
NASA Technical Reports Server (NTRS)
Technique of multivariate quantitative chemical analysis devised for use in determining relative proportions of two components mixed and sprayed together onto object to form thermally insulating foam. Potentially adaptable to other materials, especially in process-monitoring applications in which necessary to know and control critical properties of products via quantitative chemical analyses of products. In addition to chemical composition, also used to determine such physical properties as densities and strengths.
Kinchen, David G.; Capezza, Mary
Policy Manual - Chemical Safety
Keep chemicals properly labeled. Do not remove manufacturer�s label. Hazardous caution labels must be placed on all primary and secondary containers based on information from manufacturer label, MSDS, or chemical inventory evaluation. Always include the name of chemical, lot number, date opened (or date prepared or received), and expiration date and initials, as specified by CAP requirements for each specific area. Each section should follow the labeling requirements of the specific CAP checklist designated for their area.
Miniature chemical measurement systems
Prospect of microfabricated monolithic devices that accomplish complete chemical assays is enticing. Early work with microfabricated chemical analysis devices focused on separations methods. More recently reagent manipulation has been integrated with separation devices to create more powerful capabilities. Examples of procedures, other than separations, that have been demonstrated on micromachined structures include reagent mixing, dilution, and reaction, preconcentration through sample stacking and biopolymer tagging for detection. Developments in liquid phase microfabricated chemical analysis devices are reviewed.
Ramsey, J.M.
Predicting Chemical Toxicity Effects Based on Chemical-Chemical Interactions
Toxicity is a major contributor to high attrition rates of new chemical entities in drug discoveries. In this study, an order-classifier was built to predict a series of toxic effects based on data concerning chemical-chemical interactions under the assumption that interactive compounds are more likely to share similar toxicity profiles. According to their interaction confidence scores, the order from the most likely toxicity to the least was obtained for each compound. Ten test groups, each of them containing one training dataset and one test dataset, were constructed from a benchmark dataset consisting of 17,233 compounds. By a Jackknife test on each of these test groups, the 1st order prediction accuracies of the training dataset and the test dataset were all approximately 79.50%, substantially higher than the rate of 25.43% achieved by random guesses. Encouraged by the promising results, we expect that our method will become a useful tool in screening out drugs with high toxicity.
Zhang, Jian; Feng, Kai-Rui; Zheng, Ming-Yue; Cai, Yu-Dong
Apparatus for chemical synthesis
A method and apparatus for forming a chemical hydride is described and which includes a pseudo-plasma-electrolysis reactor which is operable to receive a solution capable of forming a chemical hydride and which further includes a cathode and a movable anode, and wherein the anode is moved into and out of fluidic, ohmic electrical contact with the solution capable of forming a chemical hydride and which further, when energized produces an oxygen plasma which facilitates the formation of a chemical hydride in the solution.
Kong, Peter C. (Idaho Falls, ID); Herring, J. Stephen (Idaho Falls, ID); Grandy, Jon D. (Idaho Falls, ID)
NASA Technical Reports Server (NTRS)
Chemical processes presented in this document include cleaning, pickling, surface finishes, chemical milling, plating, dry film lubricants, and polishing. All types of chemical processes applicable to aluminum, for example, are to be found in the aluminum alloy section. There is a separate section for each category of metallic alloy plus a section for non-metals, such as plastics. The refractories, super-alloys and titanium, are prime candidates for the space shuttle, therefore, the chemical processes applicable to these alloys are contained in individual sections of this manual.
Beyerle, F. J.
This chapter describes the use and potential use of biomass resources for chemical production as a means to displace petroleum use. Therefore, the scope of the discussion is limited to large scale, commodity chemical products that can have an impact on the energy market by displacing petroleum conversion to chemical products. This article does not address in detail specialty chemical products whose limited market would have minimal impact on energy markets; nor does it describe in detail the use of biomass for material products such as cellulosic fiber for paper or lignocellulosic material for construction materials. The use of biomass for production of a vast array of specialty chemicals based on unique biochemical structures is another part of the overall concept of a sustainable economy, but is outside the scope of this article. Chemical production from biomass is an energy issue in that biomass-derived chemicals can result in a significant impact on the petroleum requirement for petrochemicals used in modern society. Petroleum thus displaced is available for use in the energy market. Petroleum utilization for chemicals production is reported at 14% of the petroleum market in the United States. Displacement of a significant fraction of this chemical synthesis from petroleum can provide an important impact on the overall market. In 1998 the U.S. Department of Energy stated as its goal the production of at least 10% of the basic chemical building blocks from plant-derived renewables by the year 2020 (a five-fold increase) and 50% by 2050 (another five-fold increase). In the long run, utilization of renewable carbon sources for the chemical requirements of society is the only option as fossil sources become more scarce.
Elliott, Douglas C.
Purpose of this article is to show that erroneous conclusions may be reached from studies or routine tests with organic chemicals at the levels often employed for predicting chemical fate in nature. These errors in extrapolation from high to low concentration may occur in routine...
ERIC Educational Resources Information Center
This paper provides nine short chemically based puzzles or problems extensible for use with students from middle school to college. Some of these will strengthen students' recognition of individual elements and element names. Others require students to focus on the salient properties of given chemical elements.
Thomas, Nicholas C.
Recent chemical and process plant disasters have heightened awareness of the potential hazards associated with their operation. This book provides a comprehensive examination of those hazards - the potential risks they pose and the consequences of chemical disasters. Examined are the circumstances in which potential risks may be realized; how the hazards can be eliminated; or, where this is not
CIS: Chemical Information System.
National Technical Information Service (NTIS)
This product is comprised of the source code for both the online retrieval software and the data base processing and generation software for many of the NIH/EPA CIS (Chemical Information System) components. Software for the CIS Chemical Registry System is...
In theory, coal can provide all the chemical feedstocks now derived from oil; however, coal-chemistry technology has become outdated and needs to be improved to meet today's economic and technical demands. To bridge this gap, this collection of essays (translated from German) presents the current possibilities for producing organic chemicals from coal and suggests some routes for future developmental work.
J. Falbe; E. Ahland; G. Baron
Forward chemical genetic screening.
Chemical genetics utilizes small molecules to perturb biological processes. Unlike conventional genetics methods, which involve the alteration of genetic information mostly with lasting effects, chemical genetics allows temporary and reversible alterations of biological processes. Furthermore, it enables the alteration of biological processes in a dose-dependent manner, providing an advantage over conventional genetics. In the present chapter, the general procedures of forward chemical genetic screening are described. Forward chemical genetic screening can be performed in three steps. The first step involves the identification of small molecules that induce phenotypic or physiological changes in a biological system from a chemical library. In the second step, cellular targets that interact with the isolated chemical, which are mostly proteins, are identified. Although several methods can be applied in the second step, the most common one is affinity pull-down assay using a target protein that binds to the isolated compound. However, affinity pull-down of a target protein is a formidable barrier in forward chemical genetics. We introduced a tagged chemical library approach that significantly facilitates the identification of target proteins. The third step consists of the validation of the target protein, which should include the assessment of target specificity. This step is critical because small molecules often show pleiotropic effects due to low specificity. The specificity test may include a competition assay using cold competitors and a genetic study using mutants or transgenic lines modified for the cellular target. PMID:24057378
Choi, Hyunmo; Kim, Jun-Young; Chang, Young Tae; Nam, Hong Gil
Great Lakes: Chemical Monitoring
ERIC Educational Resources Information Center
The Tenth Great Lakes Regional Meeting of the American Chemical Society met to assess current Chemical Research activity in the Great Lakes Basin, and addressed to the various aspects of the theme, Chemistry of the Great Lakes. Research areas reviewed included watershed studies, atmospheric and aquatic studies, and sediment studies. (BT)
Delfino, Joseph J.
Difficult Decisions: Chemical Warfare.
ERIC Educational Resources Information Center
Gives the background history and chemistry of modern day chemical warfare from World War I to the present. Provides discussion questions to stimulate deeper thinking on the issue. Contains a discussion activity called "Can New Chemical Weapons Lead to Humane Warfare?" (CW)
Slesnick, Irwin L.; Miller, John A.
NSDL National Science Digital Library
The phenomenon is a chemical reaction between sugar and sulfuric acid. The demonstration (a discrepant event) compares the way sugar and water interact when combined (physical change) to the way sugar and sulfuric acid interact when combined (chemical change). In part II, students are given additional substances and changes to observe.
ERIC Educational Resources Information Center
Discusses the dependencies of people on chemicals in various aspects of life. Describes some of the natural and synthetic chemicals currently used in food production, clothing, shelter, travel and exploration, sports and recreation, ventilation, heating and cooling, communications, decoration, sanitation, and education. (TW)
Seymour, Raymond B.
Misconceptions of chemical equilibrium
Those propositions deemed necessary for an understanding of chemical equilibrium and Le Chatelier's Principle were defined by the investigators and validated.Thirty, Year 12 Western Australian chemistry students (17 years of age) who had studied chemical equilibrium were interviewed and students� responses were coded into various categories of misconception that had been identified. The most significant misconceptions revealed by the study
Mark W. Hackling; Patrick J. Garnett
Chemical Reference Literature.
ERIC Educational Resources Information Center
An innovative and effective laboratory experiment of chemical reference literature is reported. The objectives of the experiment are to acquaint the first term student of college chemistry with the vast source of chemical literature that is available to him; to raise the general level of scientific literacy of these first term college students;�
Young, Shirley M.
Recognizing Chemical Hazards Module
NSDL National Science Digital Library
The Center for the Advancement of Process Technology presents this free sample module on recognizing chemical hazards. It focuses on chemical hazards specific to process industries, and their impact on safety, health and the environment. The material also introduces the purpose and components of an MSDS.
Microorganisms and Chemical Pollution
ERIC Educational Resources Information Center
Discusses the importance of microorganisms in chemical pollution and pollution abatement. Selected chemical pollutants are chosen to illustrate that microorganisms synthesize hazardous substances from reasonably innocuous precursors, while others act as excellent environmental decontaminating agents by removing undesirable natural and synthetic�
Alexander, M.
The increasing availability of data related to genes, proteins and their modulation by small molecules, paralleled by the emergence of simulation tools in systems biology, has provided a vast amount of biological information. However, there is a critical need to develop cheminformatics tools that can integrate chemical knowledge with these biological databases, with the goal of creating systems chemical biology.
Oprea, Tudor I.; Tropsha, Alexander; Faulon, Jean-Loup; Rintoul, Mark D.
We have developed a capability to make real time concentration measurements of individual chemicals in a complex mixture using a multispectral laser remote sensing system. Our chemical recognition and analysis software consists of three parts: (1) a rigorous multivariate analysis package for quantitative concentration and uncertainty estimates, (2) a genetic optimizer which customizes and tailors the multivariate algorithm for a particular application, and (3) an intelligent neural net chemical filter which pre-selects from the chemical database to find the appropriate candidate chemicals for quantitative analyses by the multivariate algorithms, as well as providing a quick-look concentration estimate and consistency check. Detailed simulations using both laboratory fluorescence data and computer synthesized spectra indicate that our software can make accurate concentration estimates from complex multicomponent mixtures. even when the mixture is noisy and contaminated with unknowns.
Wagner, J.S.; Trahan, M.W.; Nelson, W.E.; Hargis, P.J. Jr.; Tisone, G.C.
We have developed a capability to make real time concentration measurements of individual chemicals in a complex mixture using a multispectral laser remote sensing system. Our chemical recognition and analysis software consists of three parts: (1) a rigorous multivariate analysis package for quantitative concentration and uncertainty estimates, (2) a genetic optimizer which customizes and tailors the multivariate algorithm for a particular application, and (3) an intelligent neural net chemical filter which pre-selects from the chemical database to find the appropriate candidate chemicals for quantitative analyses by the multivariate algorithms, as well as providing a quick-look concentration estimate and consistency check. Detailed simulations using both laboratory fluorescence data and computer synthesized spectra indicate that our software can make accurate concentration estimates from complex multicomponent mixtures, even when the mixture is noisy and contaminated with unknowns.
Wagner, J.S.; Trahan, M.W.; Nelson, W.E.; Hargis, P.H. Jr.; Tisone, G.C.
Tortuous path chemical preconcentrator
A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.
Manginell, Ronald P. (Albuquerque, NM); Lewis, Patrick R. (Albuquerque, NM); Adkins, Douglas R. (Albuquerque, NM); Wheeler, David R. (Albuquerque, NM); Simonson, Robert J. (Cedar Crest, NM)
Predicting the behavior of living organisms is an enormous challenge given their vast complexity. Efforts to model biological systems require large datasets generated by physical binding experiments and perturbation studies. Genetic perturbations have proven important and are greatly facilitated by the advent of comprehensive mutant libraries in model organisms. Small-molecule chemical perturbagens provide a complementary approach, especially for systems that lack mutant libraries, and can easily probe the function of essential genes. Though single chemical or genetic perturbations provide crucial information associating individual components (for example, genes, proteins or small molecules) with pathways or phenotypes, functional relationships between pathways and modules of components are most effectively obtained from combined perturbation experiments. Here we review the current state of and discuss some future directions for �combination chemical genetics�, the systematic application of multiple chemical or mixed chemical and genetic perturbations, both to gain insight into biological systems and to facilitate medical discoveries.
Lehar, Joseph; Stockwell, Brent R; Giaever, Guri; Nislow, Corey
Idaho Chemical Processing Plant safety document ICPP hazardous chemical evaluation
This report presents the results of a hazardous chemical evaluation performed for the Idaho Chemical Processing Plant (ICPP). ICPP tracks chemicals on a computerized database, Haz Track, that contains roughly 2000 individual chemicals. The database contains information about each chemical, such as its form (solid, liquid, or gas); quantity, either in weight or volume; and its location. The Haz Track
Chemical process hazards analysis
The Office of Worker Health and Safety (EH-5) under the Assistant Secretary for the Environment, Safety and Health of the US Department (DOE) has published two handbooks for use by DOE contractors managing facilities and processes covered by the Occupational Safety and Health Administration (OSHA) Rule for Process Safety Management of Highly Hazardous Chemicals (29 CFR 1910.119), herein referred to as the PSM Rule. The PSM Rule contains an integrated set of chemical process safety management elements designed to prevent chemical releases that can lead to catastrophic fires, explosions, or toxic exposures. The purpose of the two handbooks, ``Process Safety Management for Highly Hazardous Chemicals`` and ``Chemical Process Hazards Analysis,`` is to facilitate implementation of the provisions of the PSM Rule within the DOE. The purpose of this handbook ``Chemical Process Hazards Analysis,`` is to facilitate, within the DOE, the performance of chemical process hazards analyses (PrHAs) as required under the PSM Rule. It provides basic information for the performance of PrHAs, and should not be considered a complete resource on PrHA methods. Likewise, to determine if a facility is covered by the PSM rule, the reader should refer to the handbook, ``Process Safety Management for Highly Hazardous Chemicals`` (DOE- HDBK-1101-96). Promulgation of the PSM Rule has heightened the awareness of chemical safety management issues within the DOE. This handbook is intended for use by DOE facilities and processes covered by the PSM rule to facilitate contractor implementation of the PrHA element of the PSM Rule. However, contractors whose facilities and processes not covered by the PSM Rule may also use this handbook as a basis for conducting process hazards analyses as part of their good management practices. This handbook explains the minimum requirements for PrHAs outlined in the PSM Rule. Nowhere have requirements been added beyond what is specifically required by the rule.
Chemical reactions with aerosols
NASA Astrophysics Data System (ADS)
Chemical reactions of aerosol droplets with vapors are discussed. Examples are given in which liquid aerosols of 1-octadecene of narrow size distribution are converted to 1,2-dibromooctadecane with bromine vapor. It was shown that the chemical reaction in the droplet controls the kinetics of this process. The application of chemical reactions with aerosols to the formation of pure, uniform spherical particles of metal oxides is also described. Droplets of metal alkoxides rapidly react with water vapor to yield well-defined powders. The technique was used to prepare titanium dioxide, aluminum oxide, and particles consisting of both metal oxides. This procedure allows generation of powders of predetermined size and composition.
Matijevi?, Egon
Among the Weapons of Mass Destruction, chemical warfare (CW) is probably one of the most brutal created by mankind in comparison with biological and nuclear warfare. Chemical weapons are inexpensive and are relatively easy to produce, even by small terrorist groups, to create mass casualties with small quantities. The characteristics of various CW agents, general information relevant to current physical as well as medical protection methods, detection equipment available and decontamination techniques are discussed in this review article. A brief note on Chemical Weapons Convention is also provided. PMID:21829312
Ganesan, K; Raza, S K; Vijayaraghavan, R
NSDL National Science Digital Library
Chemical Patents Plus, an information retrieval service provided by Chemical Abstracts, is available via the Web. After registering, interested users can freely search and receive title and abstract information for chemical patents going back to 1971. Other options, such as patent number, front page and all claims, and complete patent, are fee based. The service is available from 6:00 p.m. Sunday through 10:00 p.m. Friday and from 3:00 a.m through 6:00 p.m. Saturday.
Short wavelength chemical lasers
Experimental results on the operation of HF chemical lasers on the v = 2 to v = 0 overtone transitions are presented. Two separate CW laser devices with gain lengths of 15 and 30 cm produced 21 and 56 W of overtone power. The comparable power on fundamental transitions of the same lasers was 97 and 180 W. Thus, these overtone HF lasers produce 22 and 31 percent of the available fundamental power, much higher percentages than previous overtone chemical lasers. The implications of this new short wavelength chemical laser for high power lasers are discussed briefly. 17 references.
Jeffers, W.Q.
NASA Technical Reports Server (NTRS)
The Chemical Management Team is responsible for ensuring compliance with the OSHA Laboratory Standard. The program at Lewis Research Center (LeRC) evolved over many years to include training, developing Standard Operating Procedures (SOPS) for each laboratory process, coordinating with other safety and health organizations and teams at the Center, and issuing an SOP binder. The Chemical Hygiene Policy was first established for the Center. The Chemical Hygiene Plan was established and reviewed by technical, laboratory and management for viability and applicability to the Center. A risk assessment was conducted for each laboratory. The laboratories were prioritized by order of risk, higher risk taking priority. A Chemical Management Team staff member interviewed the lead researcher for each laboratory process to gather the information needed to develop the SOP for the process. A binder containing the Chemical Hygiene Plan, the SOP, a map of the laboratory identifying the personal protective equipment and best egress, and glove guides, as well as other guides for safety and health. Each laboratory process has been captured in the form of an SOP. The chemicals used in the procedure have been identified and the information is used to reduce the number of chemicals in the lab. The Chemical Hygiene Plan binder is used as a training tool for new employees. LeRC is in compliance with the OSHA Standard. The program was designed to comply with the OSHA standard. In the process, we have been able to assess the usage of chemicals in the laboratories, as well as reduce or relocate the chemicals being stored in the laboratory. Our researchers are trained on the hazards of the materials they work with and have a better understanding of the hazards of the process and what is needed to prevent any incident. From the SOP process, we have been able to reduce our chemical inventory, determine and implement better hygiene procedures and equipment in the laboratories, and provide specific training to our employees. As a result of this program, we are adding labeling to the laboratories for emergency responders and initiating a certified chemical user program.
Mayor, Antoinette C.
Industrial Chemicals and Chemical Feedstocks from Wood Pulping Wastewaters.
National Technical Information Service (NTIS)
A number of industrial chemicals and chemical feedstocks can be made from wood pulping wastewaters by fermentation. The chemicals which can be made include lactic acid, and acrylic acid feedstock; neutral solvents having wide industrial use e.g. butanol, ...
A. L. Compere W. L. Griffith
Chemical Demilitarization - Assembled Chemical Weapons Assessment (ACWA): Root Cause Analysis.
National Technical Information Service (NTIS)
The Chemical Demilitarization - Assembled Chemical Weapons Alternatives (ACWA) program is responsible for the destruction of the chemical weapons stored in Pueblo, CO and Blue Grass, KY. In June 2010, the Program Manager (PM) for the ACWA program notified...
C. L. O'Connell J. S. Byun P. F. Bronson
Chemical hydrogen fluoride lasers
NASA Astrophysics Data System (ADS)
A brief review of the investigation results of chemical lasers based on the chain and nonchain reaction of fluorine with hydrogen (deuterium) made in the Russian Federal Nuclear Center (VNIIEF) is presented in this report.
Borisov, V. P.; Velikanov, S. D.; Zapolsky, A. F.; Kormer, S. B.; Synitsin, M. V.; Urlin, Vitali D.; Frolov, Y. N.; Shurov, V. V.
Chemical Educators Ponder Innovations
ERIC Educational Resources Information Center
Discusses topics presented at the Fourth Biennial Conference on Chemical Education, which included curriculum and course design, pedagogical methodology, computers, instructional aids, the environment and the history of chemistry. (MLH)
Worthy, Ward
National Technical Information Service (NTIS)
The phase-alternated experiment in liquids, a multiple-pulse NMR experiment capable of scaling chemical shifts, is examined theoretically and experimentally. The theory of the experiment is worked out using both the average-Hamiltonian and classical magne...
J. D. Ellett J. S. Waugh
Chemical Principles Exemplified
ERIC Educational Resources Information Center
Collection of two short descriptions of chemical principles seen in life situations: the autocatalytic reaction seen in the bombardier beetle, and molecular potential energy used for quick roasting of beef. Brief reference is also made to methanol lighters. (PS)
Plumb, Robert C.
Chemical warfare agents are compounds of different chemical structures. Simple molecules such as chlorine as well as complex structures such as ricin belong to this group. Nerve agents, vesicants, incapacitating agents, blood agents, lung-damaging agents, riot-control agents and several toxins are among chemical warfare agents. Although the use of these compounds is strictly prohibited, the possible misuse by terrorist groups is a reality nowadays. Owing to this fact, knowledge of the basic properties of these substances is of a high importance. This chapter briefly introduces the separate groups of chemical warfare agents together with their members and the potential therapy that should be applied in case someone is intoxicated by these agents. PMID:20358695
Kuca, Kamil; Pohanka, Miroslav
National Technical Information Service (NTIS)
Continuous filament ceramic composites are enabling new, high temperature structural applications. Chemical vapor infiltration methods for producing these composites are being studied, with the complexity of filament weaves and deposition chemistry merged...
T. M. Besmann D. P. Stinton R. A. Lowden
Reducing Household Chemical Risks
NSDL National Science Digital Library
This series of public service videos from the National Institute of Environmental Health Sciences provides quick solutions and action steps to minimize exposure to pesticides, chemical contaminants, and secondhand smoke.
Foundation, Wgbh E.
Chemical dependence - resources
Drug abuse - resources; Resources - chemical dependence ... The following organizations are a good resource for information on drug dependence: Narcotics Anonymous - www.na.org National Council on Alcoholism and Drug Dependence - www.ncadd.org National Institute ...
This chapter contains sections titled: Chemicals from Coke Oven Distillate; The Fischer-Tropsch Reaction; Coal Hydrogenation; Substitute Natural Gas (SNG); Synthesis Gas Technology; Calcium Carbide; Coal and the Environment; and Notes and References
Harold A. Wittcoff; Bryan G. Reuben; Jeffrey S. Plotkin
NSDL National Science Digital Library
The STP ChemicalDemon program displays a histogram of the energy of a demon that exchanges energy and particles with a one-dimensional lattice of particles. The purpose of this simulation is to understand how the demon acts as an ideal thermometer and ideal measurement of the chemical potential. The default system is a lattice of length L = 100 with N = 100 particles, an energy E = 200 and non interacting particles. STP ChemicalDemon is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double-clicking the stp_ChemicalDemon.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.
Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne
Legendary Chemical Aphrodisiacs.
ERIC Educational Resources Information Center
Presents a survey of the literature and a summary of information regarding aphrodisiacs. Chemical compounds are discussed as groups of plant natural products, animal natural products, and synthetic products. (CS)
Waddell, Thomas G.; And Others
Chemical Reactions and Pancakes
NSDL National Science Digital Library
Students will compare ingredients in two different pancake recipes, then taste the difference. We will talk about the chemical reaction that happened when the recipes are mixed and why there are bubbles in the pancakes.
Safer Science: Chemical Storage
NSDL National Science Digital Library
Using chemicals safely requires a number of things, including current inventory control, appropriate labeling and storage segregation, ongoing inspections, and more. How can a science teacher find the appropriate storage information? Read on. This month's
Roy, Ken
NASA Technical Reports Server (NTRS)
This viewgraph presentation is a review of the career paths for chemicals engineer at NASA (specifically NASA Johnson Space Center.) The author uses his personal experience and history as an example of the possible career options.
Collins, Jacob
Power plant chemical technology.
National Technical Information Service (NTIS)
17 contributions covering topies of fossil fuel combustion, flue gas cleaning, power plant materials, corrosion, water/steam cycle chemistry, monitoring and control were presented at the annual meeting devoted to Power Plant Chemical Technology 1996 at Ko...
Sawmill chemicals and carcinogenesis.
Workers in wood industries are exposed to variable medleys of chemicals, both natural and synthetic. Additional exposures include fungi, bacteria, bark and wood dusts, solvents, paints, and various other wood coatings. These individual and conglomerate exposures have been associated with diverse occupational illnesses and hazards, including cancers. In this commentary, I summarize both experimental and epidemiologic carcinogenesis results for several chemicals used in the wood industry, as well as for wood dust. Working in the wood industries entails excess risks of cancers, among other diseases and workplace injuries. A key to preventing occupationally and environmentally associated cancers, as in the wood industries, is avoiding exposures to chemicals and wood dusts and, in particular, chemicals known to cause cancer in animals or/and humans.
Huff, J
Chemical and Thermal Analysis.
National Technical Information Service (NTIS)
During the past six months we have conducted significant research in several domains in order to clarify and understanding the aging and chemical failure mechanism of thermoplastics (PVDF or Tefzel) for pipes. We organized numerous analytical studies with...
J. W. Bulluck R. A. Rushing
National Technical Information Service (NTIS)
This final report describes a database that supports the development, engineering and manufacturing of dependable chemical sensors which include fiber-optics in the design and which are suitable for use in the field by technicians. Inexperienced investiga...
W. F. Arendale R. Hatcher Y. Garlington J. Harwell T. Everett
NSDL National Science Digital Library
Published since 1924,the Journal of Chemical Education's mission is to help chemistry teachers stay current with research advances, and to be informed about new ideas in teaching methodologies and course organization. To achieve this mission, JCE online provides a plethora of resources on chemistry and chemical education. JCE's digital library is especially helpful and includes detailed information on molecules, mathematic equations, and much more.
Quality of Chemical Measurements
NSDL National Science Digital Library
The International Union of Pure and Applied Chemistry's online newsletter, Chemistry International, posts this article about the problem of wide variation in chemical trace and catalyst measurements. This is important because such data are increasingly used in industry decision-making. In the words of the authors, "This article provides 'snapshot' pictures of chemical measurement (un)reliability, with many practical, societal implications." All text is in HTML.
Quality of Chemical Measurements
NSDL National Science Digital Library
The International Union of Pure and Applied Chemistry's online newsletter, Chemistry International, posts this article about the problem of wide variation in chemical trace and catalyst measurements. This is important because such data are increasingly used in industry decision-making. In the words of the authors, "This article provides 'snapshot' pictures of chemical measurement (un)reliability, with many practical, societal implications." All text is in HTML.
Chemical contamination remote sensing
NASA Technical Reports Server (NTRS)
A ground mobile laser test bed system was assembled to assess the feasibility of detection of various types of chemical contamination using Differential Scattering (DISC) and Differential Absorption (DIAL) Lidar techniques. Field experiments with the test bed system using chemical simulants were performed. Topographic reflection and range resolved DIAL detection of vapors as well as DISC detection of aerosols and surface contamination were achieved. Review of detection principles, design of the test bed system, and results of the experiments are discussed.
Carrico, J. P.; Phelps, K. R.; Webb, E. N.; Mackay, R. A.; Murray, E. R.
Chemical warfare agents (CWA's) are defined as any chemical substance whose toxic properties are utilised to kill, injure or incapacitate an enemy in warfare and associated military operations. Chemical agents have been used in war since times immemorial, but their use reached a peak during World War I. During World War II only the Germans used them in the infamous gas chambers. Since then these have been intermittently used both in war and acts of terrorisms. Many countries have stockpiles of these agents. There has been a legislative effort worldwide to ban the use of CWA's under the chemical weapons convention which came into force in 1997. However the manufacture of these agents cannot be completely prohibited as some of them have potential industrial uses. Moreover despite the remedial measures taken so far and worldwide condemnation, the ease of manufacturing these agents and effectiveness during combat or small scale terrorist operations still make them a powerful weapon to reckon with. These agents are classified according to mechanism of toxicity in humans into blister agents, nerve agents, asphyxiants, choking agents and incapacitating/behavior altering agents. Some of these agents can be as devastating as a nuclear bomb. In addition to immediate injuries caused by chemical agents, some of them are associated with long term morbidities and psychological problems. In this review we will discuss briefly about the historical background, properties, manufacture techniques and industrial uses, mechanism of toxicity, clinical features of exposure and pharmacological management of casualties caused by chemical agents. PMID:21783898
Chauhan, S; Chauhan, S; D'Cruz, R; Faruqi, S; Singh, K K; Varma, S; Singh, M; Karthik, V
Computational Systems Chemical Biology
There is a critical need for improving the level of chemistry awareness in systems biology. The data and information related to modulation of genes and proteins by small molecules continue to accumulate at the same time as simulation tools in systems biology and whole body physiologically-based pharmacokinetics (PBPK) continue to evolve. We called this emerging area at the interface between chemical biology and systems biology systems chemical biology, SCB (Oprea et al., 2007). The overarching goal of computational SCB is to develop tools for integrated chemical-biological data acquisition, filtering and processing, by taking into account relevant information related to interactions between proteins and small molecules, possible metabolic transformations of small molecules, as well as associated information related to genes, networks, small molecules and, where applicable, mutants and variants of those proteins. There is yet an unmet need to develop an integrated in silico pharmacology / systems biology continuum that embeds drug-target-clinical outcome (DTCO) triplets, a capability that is vital to the future of chemical biology, pharmacology and systems biology. Through the development of the SCB approach, scientists will be able to start addressing, in an integrated simulation environment, questions that make the best use of our ever-growing chemical and biological data repositories at the system-wide level. This chapter reviews some of the major research concepts and describes key components that constitute the emerging area of computational systems chemical biology.
Oprea, Tudor I.; May, Elebeoba E.; Leitao, Andrei; Tropsha, Alexander
Chemical Equilibrium And Transport (CET)
NASA Technical Reports Server (NTRS)
Powerful, machine-independent program calculates theoretical thermodynamic properties of chemical systems. Aids in design of compressors, turbines, engines, heat exchangers, and chemical processing equipment.
Mcbride, B. J.
Understanding the motions of the constituent atoms in reacting molecules lies at the heart of chemistry and is the central focus of chemical reaction dynamics. The most detailed questions one can ask are about the evolution of molecules prepared in a single quantum state to products in individual states, and both calculations and experiments are providing such detailed understanding of increasingly complex systems. A central goal of these studies is uncovering the essential details of chemical change by removing the averaging over the initial conditions that occurs in many cases. Such information provides an exquisite test of theory and helps paint pictures of complicated chemical transformations. The goal of this Special Feature is to provide a snapshot of a portion of the field of chemical reaction dynamics. Much of the work presented here emphasizes a close interplay of experiment and theory in ways that sharpen the conclusions of both and animate future studies. The articles do not completely cover the rich field of chemical reaction dynamics but rather provide a glimpse of some of the emerging insights.
Crim, F. Fleming
Chemically enhanced oil recovery
Yet when conducted according to present state of the art, chemical flooding (i.e., micellar/polymer flooding, surfactant/polymer flooding, surfactant flooding) can mobilize more residual crude oil than any other method of enhanced oil recovery. It also is one of the most expensive methods of enhanced oil recovery. This contribution will describe some of the technology that comprises the state of the art technology that must be adhered to if a chemical flood is to be successful. Although some of the efforts to reduce cost and other points are discussed, the principle focus is on technical considerations in designing a good chemical flooding system. The term chemical flooding is restricted here to methods of enhanced oil recovery that employs a surfactant, either injected into the oil reservoir or generated in situ, primarily to reduce oil-water interfacial tension. Hence, polymer-water floods for mobility or profile control, steam foams, and carbon dioxide foams are excluded. Some polymer considerations are mentioned because they apply to providing mobility control for chemical flooding systems.
Nelson, R.C.
Inspired by the use of hybrid cellular automata in modeling cancer, we introduce a generalization of evolutionary games in which cells produce and absorb chemicals, and the chemical concentrations dictate the death rates of cells and their fitnesses. Our long term aim is to understand how the details of the interactions in a system with n species and m chemicals translate into the qualitative behavior of the system. Here, we study two simple 2�2 games with two chemicals and revisit the two and three species versions of the one chemical colicin system studied earlier by Durrett and Levin (1997). We find that in the 2�2 examples, the behavior of our new spatial model can be predicted from that of the mean field differential equation using ideas of Durrett and Levin (1994). However, in the three species colicin model, the system with diffusion does not have the coexistence which occurs in the lattices model in which sites interact with only their nearest neighbors. PMID:24513098
Aristotelous, Andreas C; Durrett, Richard
Biological and Chemical Security
The LLNL Chemical & Biological National Security Program (CBNP) provides science, technology and integrated systems for chemical and biological security. Our approach is to develop and field advanced strategies that dramatically improve the nation's capabilities to prevent, prepare for, detect, and respond to terrorist use of chemical or biological weapons. Recent events show the importance of civilian defense against terrorism. The 1995 nerve gas attack in Tokyo's subway served to catalyze and focus the early LLNL program on civilian counter terrorism. In the same year, LLNL began CBNP using Laboratory-Directed R&D investments and a focus on biodetection. The Nunn-Lugar-Domenici Defense Against Weapons of Mass Destruction Act, passed in 1996, initiated a number of U.S. nonproliferation and counter-terrorism programs including the DOE (now NNSA) Chemical and Biological Nonproliferation Program (also known as CBNP). In 2002, the Department of Homeland Security was formed. The NNSA CBNP and many of the LLNL CBNP activities are being transferred as the new Department becomes operational. LLNL has a long history in national security including nonproliferation of weapons of mass destruction. In biology, LLNL had a key role in starting and implementing the Human Genome Project and, more recently, the Microbial Genome Program. LLNL has over 1,000 scientists and engineers with relevant expertise in biology, chemistry, decontamination, instrumentation, microtechnologies, atmospheric modeling, and field experimentation. Over 150 LLNL scientists and engineers work full time on chemical and biological national security projects.
Fitch, P J
Chemical analysis quality assurance at the Idaho Chemical Processing Plant
The Idaho Chemical Processing Plant (ICPP) is a uranium reprocessing facility operated by Westinghouse Idaho Nuclear Company for the Department of Energy at the Idaho National Engineering Laboratory (INEL). The chemical analysis support required for the plant processes is provided by a chemical analysis staff of 67 chemists, analysts, and support personnel. The documentation and defense of the chemical analysis
R. L. Hand; R. W. Anselmo; D. B. Black; J. J. Jacobson; L. C. Lewis; P. C. Marushia; F. W. Spraktes; N. R. Zack
Idaho Chemical Processing Plant safety document ICPP hazardous chemical evaluation
This report presents the results of a hazardous chemical evaluation performed for the Idaho Chemical Processing Plant (ICPP). ICPP tracks chemicals on a computerized database, Haz Track, that contains roughly 2000 individual chemicals. The database contains information about each chemical, such as its form (solid, liquid, or gas); quantity, either in weight or volume; and its location. The Haz Track database was used as the primary starting point for the chemical evaluation presented in this report. The chemical data and results presented here are not intended to provide limits, but to provide a starting point for nonradiological hazards analysis.
Harwood, B.J.
NASA Astrophysics Data System (ADS)
The Chemical Domino Demonstration is both educational and entertaining. It provides an excellent means for a review of chemical concepts at the conclusion of a general chemistry course. This demonstration consists of a number of different chemical reactions occurring in sequence in a Rube Goldberg-type apparatus. These reactions include the reduction of water by an active metal, the oxidation of a moderately active metal by an acid, reduction of metallic ions by a metal of greater activity, acid-base neutralization reactions in solution monitored with indicators, a gas-phase acid-base neutralization reaction, decomposition of a compound, precipitation of an insoluble salt, substitution reactions of coordination complexes, and pyrotechnic oxidation-reduction reactions including a hypergolic oxidation-reduction reaction, an intramolecular oxidation-reduction reaction, and the combustion of a flammable gas.
Alexander, M. Dale
Translated chemical reaction networks.
Many biochemical and industrial applications involve complicated networks of simultaneously occurring chemical reactions. Under the assumption of mass action kinetics, the dynamics of these chemical reaction networks are governed by systems of polynomial ordinary differential equations. The steady states of these mass action systems have been analyzed via a variety of techniques, including stoichiometric network analysis, deficiency theory, and algebraic techniques (e.g., Gr�bner bases). In this paper, we present a novel method for characterizing the steady states of mass action systems. Our method explicitly links a network's capacity to permit a particular class of steady states, called toric steady states, to topological properties of a generalized network called a translated chemical reaction network. These networks share their reaction vectors with their source network but are permitted to have different complex stoichiometries and different network topologies. We apply the results to examples drawn from the biochemical literature. PMID:24610094
Johnston, Matthew D
National Institute of Standards and Technology Data Gateway
SRD 17 NIST Chemical Kinetics Database (Web, free access)�� The NIST Chemical Kinetics Database includes essentially all reported kinetics results for thermal gas-phase chemical reactions. The database is designed to be searched for kinetics data based on the specific reactants involved, for reactions resulting in specified products, for all the reactions of a particular species, or for various combinations of these. In addition, the bibliography can be searched by author name or combination of names. The database contains in excess of 38,000 separate reaction records for over 11,700 distinct reactant pairs. These data have been abstracted from over 12,000 papers with literature coverage through early 2000.
Micromachined chemical jet dispenser
A dispenser for chemical fluid samples that need to be precisely ejected in size, location, and time. The dispenser is a micro-electro-mechanical systems (MEMS) device fabricated in a bonded silicon wafer and a substrate, such as glass or silicon, using integrated circuit-like fabrication technology which is amenable to mass production. The dispensing is actuated by ultrasonic transducers that efficiently produce a pressure wave in capillaries that contain the chemicals. The 10-200 .mu.m diameter capillaries can be arranged to focus in one spot or may be arranged in a larger dense linear array (.about.200 capillaries). The dispenser is analogous to some ink jet print heads for computer printers but the fluid is not heated, thus not damaging certain samples. Major applications are in biological sample handling and in analytical chemical procedures such as environmental sample analysis, medical lab analysis, or molecular biology chemistry experiments.
Swierkowski, Steve P. (Livermore, CA)
Micromachined chemical jet dispenser
A dispenser is disclosed for chemical fluid samples that need to be precisely ejected in size, location, and time. The dispenser is a micro-electro-mechanical systems (MEMS) device fabricated in a bonded silicon wafer and a substrate, such as glass or silicon, using integrated circuit-like fabrication technology which is amenable to mass production. The dispensing is actuated by ultrasonic transducers that efficiently produce a pressure wave in capillaries that contain the chemicals. The 10-200 {micro}m diameter capillaries can be arranged to focus in one spot or may be arranged in a larger dense linear array (ca. 200 capillaries). The dispenser is analogous to some ink jet print heads for computer printers but the fluid is not heated, thus not damaging certain samples. Major applications are in biological sample handling and in analytical chemical procedures such as environmental sample analysis, medical lab analysis, or molecular biology chemistry experiments. 4 figs.
Swierkowski, S.P.
Chemically programmed antibodies.
Due to their unlimited chemical diversity, small molecules can rival monoclonal antibodies (mAbs) with respect to specificity and affinity for target molecules. However, key pharmacological properties of mAbs remain unmatched by small molecules. Chemical programming strategies have been developed for site-specific and covalent conjugation of small molecules to mAbs with unique reactivity centers. In addition to blending favorable features of small molecules and mAbs, chemically programmed antibodies (cpAbs) are economically attractive because they utilize the same mAb for an almost unlimited number of target molecule specificities, reducing manufacturing costs and shortening drug discovery and development time. Preclinical studies and clinical trials have begun to demonstrate the broad utility of cpAbs for the treatment and prevention of human diseases. PMID:24630478
Rader, Christoph
Advanced Chemical Propulsion Study
NASA Technical Reports Server (NTRS)
A study was performed of advanced chemical propulsion technology application to space science (Code S) missions. The purpose was to begin the process of selecting chemical propulsion technology advancement activities that would provide greatest benefits to Code S missions. Several missions were selected from Code S planning data, and a range of advanced chemical propulsion options was analyzed to assess capabilities and benefits re these missions. Selected beneficial applications were found for higher-performing bipropellants, gelled propellants, and cryogenic propellants. Technology advancement recommendations included cryocoolers and small turbopump engines for cryogenic propellants; space storable propellants such as LOX-hydrazine; and advanced monopropellants. It was noted that fluorine-bearing oxidizers offer performance gains over more benign oxidizers. Potential benefits were observed for gelled propellants that could be allowed to freeze, then thawed for use.
Woodcock, Gordon; Byers, Dave; Alexander, Leslie A.; Krebsbach, Al
Micropharmacokinetics of chemical modifiers
Classical pharmacokinetic analysis of plasma, urine and tissue specimens continues to be of major value to the rational development of chemical modifiers of cancer treatment. However, in addition, increasingly sophisticated analytical techniques are becoming available which allow the pathways of microdistribution and micrometabolism of drugs to be traced down to the cellular and molecular level. New developments described here include flow cytometry, magnetic resonance spectroscopy, and molecular enzymology. These are predicted to have a major impact on the optimization of chemical modification. 52 references.
Workman, P.
Chemical induced intracellular hyperthermia
US Patent & Trademark Office Database
An invention relating to therapeutic pharmacological agents and methods to chemically induce intracellular hyperthermia and/or free radicals for the diagnosis and treatment of infections, malignancy and other medical conditions. The invention relates to a process and composition for the diagnosis or killing of cancer cells and inactivation of susceptible bacterial, parasitic, fungal, and viral pathogens by chemically generating heat, and/or free radicals and/or hyperthermia-inducible immunogenic determinants by using mitochondrial uncoupling agents, especially 2,4 dinitrophenol and, their conjugates, either alone or in combination with other drugs, hormones, cytokines and radiation.
Chemically derivatized semiconductor photoelectrodes
NASA Astrophysics Data System (ADS)
Semiconductor-based photoelectrochemical cells are the best man-contrived devices for the direct conversion of sunlight to electrical or chemical energy using chemically-based systems. Deliberate modification of the surface of the semiconductor photoelectrode is useful in improving the rate of desired processes and in suppressing undesirable anodic corrosion associated with photoanodes. Illustrations of the use of surface modification will be presented with specific examples coming from work with molecular-based derivatizing reagents and from the use of metals or metal oxides coated onto the photoelectrode surface.
Wrighton, M. S.
Chemical profiles of switchgrass.
Chemical analysis studies were conducted for four populations of switchgrass (Alamo, Kanlow, GA993, and GA992), Panicum virgatum L., which were partitioned into leaves, internodes, and nodes. The variations in carbohydrate compositions, lignin and extractives content, higher heating value (HHV), and the syringyl:guaiacyl ratio of switchgrass were determined. The experimental results indicated that bulk chemical profiles for the four populations of switchgrass were comparable. However, the results from three morphological components of switchgrass, leaves, internodes and nodes, provided a significant diversity among the analytical results studied. PMID:20074945
Hu, Zhoujian; Sykes, Robert; Davis, Mark F; Charles Brummer, E; Ragauskas, Arthur J
NASA Astrophysics Data System (ADS)
Applications for visible chemical lasers, which show great potential as highly efficient, wavelength agile, deployable, high brightness laser systems are discussed. These systems provide important and unique opportunities for both directed energy weapons and diagnostic applications. Issues discussed in this paper include concepts, requirements and approaches to visible chemical lasers. A survey of candidate energy transfer system is also given, with emphasis on excited NF and nitrogen driven lasers. The long term, low level investment in this techonology area during the past decade firmly establishes the opportunity for a lasing demonstration in the near term.
Perram, Glen P.
Chemical laser systems analysis
This paper presents a means by which the chemical laser device weight can be minimized with respect to its performance and the device power minimized with respect to the target range. Chemical laser performance parameters such as the specific power and nozzle power flux are then used in conjunction with weight and propagation models to determine system effectiveness. A measure of merit is given by which systems can be contrasted. An illustrative example is included in which DF and Iodine laser systems are compared for an airborne scenario. 14 references.
Doughty, J.R.
Chemical weathering in granitic environments
Factors controlling chemical weathering in granitic environments are deduced using an extensive database from the literature. Based on a transition state theory model, we evaluated the effects on chemical weathering of runoff, temperature and pH. The dependence between temperature and runoff, and chemical weathering is complicated by other factors such as the presence\\/depth of soil cover. Soil cover favors chemical
Priscia Oliva; J�rome Viers; Bernard Dupr�
NETL - Chemical Looping Reactor
NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.
Chemical Engineering in Space.
National Technical Information Service (NTIS)
The aerospace industry has long been perceived as the domain of both physicists and mechanical engineers. This perception has endured even though the primary method of providing the thrust necessary to launch a rocket into space is chemical in nature. The...
D. A. Lobmeyer B. Meneghelli
Environmental and chemical carcinogenesis
People are continuously exposed exogenously to varying amounts of chemicals that have been shown to have carcinogenic or muta- genic properties in experimental systems. Exposure can occur exogenously when these agents are present in food, air or water, and also endogenously when they are products of metabolism or pathophysiologic states such as inflammation. It has been estimated that exposure to
Gerald N. Wogana; Stephen S. Hecht; James S. Felton; Allan H. Conney; Lawrence A. Loeb
Endocrine disrupting chemicals
In the past 200 years, an enormous number of synthetic chemicals with diverse structural features have been produced for industrial, medical and domestic purposes. These chemicals, originally thought to have little or no biological toxicity, are widely used in our daily lives as well as are commonly present in foods. It was not until the first World Wildlife Federation Wingspread Conference held in 1994 were concerns about the endocrine disrupting (ED) effects of these chemicals articulated. The potential hazardous effects of endocrine disrupting chemicals (EDCs) on human health and ecological well-being are one of the global concerns that affect the health and propagation of human beings. Considerable numbers of studies indicated that endocrine disruption is linked to �the developmental basis of adult disease,� highlighting the significant effects of EDC exposure on a developing organism, leading to the propensity of an individual to develop a disease or dysfunction in later life. In this review, we intend to provide environmental, epidemiological and experimental data to associate pollutant exposure with reproductive disorders, in particular on the development and function of the male reproductive system. Possible effects of pollutant exposure on the processes of embryonic development, like sex determination and masculinization are described. In addition, the effects of pollutant exposure on hypothalamus-pituitary-gonadal axis, testicular signaling, steroidogenesis and spermatogenesis are also discussed.
Yeung, Bonnie HY; Wan, Hin T; Law, Alice YS
Visionlearning: Chemical Bonding
NSDL National Science Digital Library
This digital learning module provides an easily-understood overview of chemical bonding for users with little formal background in chemistry or physics. It explores ionic bonding through the example of sodium (an alkali metal) reacting with chlorine gas to produce common table salt. A concept simulation further illustrates the process.
Carpi, Anthony
Hazardous chemicals detection experiment
An experiment involving the production and measurement of chemical vapors released from two volatile liquid solvents and a toxic gas was conducted on December 9, 1992 at a remote site near Sacramento, California. During this experiment, measured quantities of liquid diethyl ether and acetone and hydrogen chloride gas were released under controlled conditions inside a mobile-home-type structure. Vapor concentrations of
Rowena M. Carlson; Laura Bunney; Donald N. Williams
Risks and Chemical Substances.
ERIC Educational Resources Information Center
Examines exposure to chemicals within the home and three important ways in which hazardous substances can be identified and evaluated. Suggests a rational picture of human health risks and contains an introductory discussion of reasons for exposure, epidemiology, cancer causes and patterns, animal testing, toxins, and risk. (LZ)
Blumberg, Avrom A.
NASA Technical Reports Server (NTRS)
Advanced Chemical Propulsion (ACP) provides near-term incremental improvements in propulsion system performance and/or cost. It is an evolutionary approach to technology development that produces useful products along the way to meet increasingly more demanding mission requirements while focusing on improving payload mass fraction to yield greater science capability. Current activities are focused on two areas: chemical propulsion component, subsystem, and manufacturing technologies that offer measurable system level benefits; and the evaluation of high-energy storable propellants with enhanced performance for in-space application. To prioritize candidate propulsion technology alternatives, a variety of propulsion/mission analyses and trades have been conducted for SMD missions to yield sufficient data for investment planning. They include: the Advanced Chemical Propulsion Assessment; an Advanced Chemical Propulsion System Model; a LOx-LH2 small pumps conceptual design; a space storables propellant study; a spacecraft cryogenic propulsion study; an advanced pressurization and mixture ratio control study; and a pump-fed vs. pressure-fed study.
Alexander, Leslie, Jr.
NSDL National Science Digital Library
Created by Hans Reich, professor of organic chemistry at the Uiversity of Wisconsin-Madison, this site contains a compilation of proton chemical shifts and coupling constants. This is an excellent resource for providing students familiarity with Nuclear Magnetic Resonance (NMR) Spectroscopy Data.
Reich, Hans J.
NSDL National Science Digital Library
In this lab, learners evaluate the relative effectiveness of various chemical substances (i.e. garlic powder, bathroom cleaner, mouthwash, etc.) as antimicrobial agents. Learners use the agar diffusion method to determine "zones of inhibition." This lesson guide includes background information, questions for learners, and additional activity ideas.
Fran Slowiczek, Ed D.; Peters, Pamela M.
NASA Technical Reports Server (NTRS)
Electro-chemical grinding technique has rotation speed control, constant feed rates, and contour control. Hypersonic engine parts of nickel alloys can be almost 100% machined, keeping tool pressure at virtual zero. Technique eliminates galling and permits constant surface finish and burr-free interrupted cutting.
Feagans, P. L.
Chemical Principles Exemplified
ERIC Educational Resources Information Center
This is the first of a new series of brief ancedotes about materials and phenomena which exemplify chemical principles. Examples include (1) the sea-lab experiment illustrating principles of the kinetic theory of gases, (2) snow-making machines illustrating principles of thermodynamics in gas expansions and phase changes, and (3) sunglasses that�
Plumb, Robert C.
Environmental and chemical carcinogenesis
People are continuously exposed exogenously to varying amounts of chemicals that have been shown to have carcinogenic or mutagenic properties in experimental systems. Exposure can occur exogenously when these agents are present in food, air or water, and also endogenously when they are products of metabolism or pathophysiologic states such as inflammation. It has been estimated that exposure to environmental
Gerald N. Wogan; Stephen S. Hecht; James S. Felton; Allan H. Conney; Lawrence A. Loeb
Rodents exhibit an innate fear-like behavior when they sense the chemical traces of predators. In this issue, Papes et al. (2010) report that the major urinary proteins (Mups) released by predators are detected by sensory neurons in the mouse vomeronasal organ (which also detects pheromones involved in aggression), triggering a fear response. PMID:20478249
Rodriguez, Ivan
ERIC Educational Resources Information Center
Chemical bonding is discussed from a bond energy, rather than a wave mechanics, viewpoint. This approach is considered to be more suitable for the average student. (The second part of the article will appear in a later issue of the journal.) (AL)
Sanderson, R. T.
Tourniquet associated chemical burn
Chemical burn under pneumatic tourniquet is an iatrogenic preventable injury and is rarely reported in the literature. The two important mechanisms are maceration (friction) and wetness underneath the tourniquent. In this report, our experience with two illustrative patients who presented with iatrogenic tourniquet associated burn is described.
Yang, Jae-Hyuk; Lim, Hyungtae; Yoon, Jung-Ro; Jeong, Hyeon-Il
ERIC Educational Resources Information Center
This month's column features two true stories about the use of chemicals in the middle school science classroom. The lesson of these stories is simple. Certainly, it is prudent to have age-appropriate experiences in science, given the developmental constraints of students in middle school. On the other hand, when the curriculum necessitates�
Roy, Ken
Chemical constituents of Asparagus
Asparagus species (family Liliaceae) are medicinal plants of temperate Himalayas. They possess a variety of biological properties, such as being antioxidants, immunostimulants, anti-inflammatory, antihepatotoxic, antibacterial, antioxytocic, and reproductive agents. The article briefly reviews the isolated chemical constituents and the biological activities of the plant species. The structural formula of isolated compounds and their distribution in the species studied are also given.
Negi, J. S.; Singh, P.; Joshi, G. P.; Rawat, M. S.; Bisht, V. K.
Chemical Vapor Deposition Growth.
National Technical Information Service (NTIS)
A chemical vapor deposition (CVD) reactor system with a vertical deposition chamber was used for the growth of Si films on glass, glass-ceramic, and polycrystalline ceramic substrates. Silicon vapor was produced by pyrolysis of SiH4 in a H2 or He carrier ...
R. P. Ruth, H. M. Manasevit, J. L. Kenty, L. A. Moudy, W. I. Simpson
Policy Manual - Chemical Storage
OSHA requires the establishment of special �designated areas� in laboratories for the storage of chemical substances of moderate to high chronic toxicity (and including carinogens, teratogens, and embryotoxins). A �designated area� may be a cabinet, desiccator, fume hood, or refrigerator where toxic substances can be stored or used. A sign should be present to alert other laboratory personnel that such substances are present.
National Technical Information Service (NTIS)
The purpose of this study was to monitor the effects of diluents on a HCl laser. The initial plans were to obtain an HCl laser with a mixture of helium, hydrogen, and chlorine, and then try other chemicals. However, it was found in the present study that ...
J. K. McDonald
Accurate quantum chemical calculations
NASA Technical Reports Server (NTRS)
An important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.
The development of effective, non-toxic (local and systemic) methods for the rapid chemical (enzymatic and non-enzymatic) debridement of third degree burns would dramatically reduce the morbidity and mortality of severely burned patients. Sepsis is still the major cause of death of patients with extensive deep burns. The removal of the devitalized tissue, without damage to unburned skin or skin only partially injured by burning, and in ways which would permit immediate (or very prompt) skin grafting, would lessen substantially the problems of sepsis, speed convalescence and the return of these individuals to society as effective human beings, and would decrease deaths. The usefulness and limitations of surgical excision for patients with extensive third degree burns are discussed. Chemical debridement lends itself to complementary use with surgical excision and has the potential advantage over surgical excision in not requiring anesthesia or a formal surgical operation. The authors' work with the chemical debridement of burns, in particular the use of Bromelain, indicates that this approach will likely achieve clinical usefulness. The experimental studies indicate that rapid controlled debridement, with minimal local and systemic toxicity, is possible, and that effective chemotherapeutic agents may be combined with the Bromelain without either interfering with the actions of the other. The authors believe that rapid (hours) debridement accomplished by the combined use of chemical debriding and chemotherapeutic agents will obviate the possibility of any increase in infection, caused by the use of chemical agents for debridement, as reported for Paraenzyme21 and Travase.39,48 It is possible that the short term use of systemic antibiotics begun just before and continued during, and for a short time after, the rapid chemical debridement may prove useful for the prevention of infection, as appears to be the case for abdominal operations of the clean-contaminated and contaminated types. ImagesFigs. 1a-c.Fig. 1b.Fig. 1c.Fig. 2.Fig. 3.Fig. 4.Fig. 5.Fig. 6.Fig. 7.Fig. 8.Fig. 9a.Fig. 9B.Fig. 10.Fig. 11.Figs. 12a-c.Fig. 12b.Fig. 12c.Figs. 14a-c.Fig. 14b.Fig. 14c.Figs. 15a-c.Fig. 15b.Fig. 15c.
Levenson, Stanley M.; Kan, Dorinne; Gruber, Charles; Crowley, Leo V.; Lent, Richard; Watford, Alvin; Seifter, Eli
Synthetic chemicals are now being incorporated into the earth's ecosystems at a rate and in such manners as to alarm environmentalists. These chemicals are the uncontrolled waste products of a technological society. Most prominent among them at the present time are organochlorine, organomercurial and lead compounds. Persistent members of these groups disperse in water, air and animal tissues. Also they have the capacity for concentration in animal food chains, thereby reversing the historical expectation of the dilution and degradation of wastes. Examples of damage from environmental residues to man are at this stage speculative but documentation from effects on wild species is abundant. Already several species of birds seem on their way to extinction. These wild species constitute a gratuitous monitoring system which already has signaled clear warnings for the welfare of man.
Rudd, Robert L.
Biocatalysis for biobased chemicals.
The design and development of greener processes that are safe and friendly is an irreversible trend that is driven by sustainable and economic issues. The use of Biocatalysis as part of a manufacturing process fits well in this trend as enzymes are themselves biodegradable, require mild conditions to work and are highly specific and well suited to carry out complex reactions in a simple way. The growth of computational capabilities in the last decades has allowed Biocatalysis to develop sophisticated tools to understand better enzymatic phenomena and to have the power to control not only process conditions but also the enzyme's own nature. Nowadays, Biocatalysis is behind some important products in the pharmaceutical, cosmetic, food and bulk chemicals industry. In this review we want to present some of the most representative examples of industrial chemicals produced in vitro through enzymatic catalysis. PMID:24970192
de Regil, Rub�n; Sandoval, Georgina
Chemical Education Digital Library
NSDL National Science Digital Library
Benzene rings and other aspects of chemistry come alive with these "living textbooks." This collection of key chemistry documents and primers is made possible via the Chemical Education Digital Library (ChemEd DL) and it contains eight separate items. They are called "living" because they are updated by their owners and those responsible for their continued success. Users will find "Practice in Thinking: A Laboratory Course in Introductory Chemistry," "Chemistry Leaflets," and "Wiki: Quantum States of Atoms and Molecules" here for their consideration. The Chemistry Leaflets provide an interesting wrinkle as they were originally published between 1927 and the mid-1940s. Visitors shouldn't miss "Chemical Principles through Integrated Multiple Exemplars (ChemPRIME)" as it is designed so that general chemistry concepts can be presented in an order that reflects the conceptual structure of the discipline.
Biocatalysis for Biobased Chemicals
The design and development of greener processes that are safe and friendly is an irreversible trend that is driven by sustainable and economic issues. The use of Biocatalysis as part of a manufacturing process fits well in this trend as enzymes are themselves biodegradable, require mild conditions to work and are highly specific and well suited to carry out complex reactions in a simple way. The growth of computational capabilities in the last decades has allowed Biocatalysis to develop sophisticated tools to understand better enzymatic phenomena and to have the power to control not only process conditions but also the enzyme�s own nature. Nowadays, Biocatalysis is behind some important products in the pharmaceutical, cosmetic, food and bulk chemicals industry. In this review we want to present some of the most representative examples of industrial chemicals produced in vitro through enzymatic catalysis.
de Regil, Ruben; Sandoval, Georgina
NASA Technical Reports Server (NTRS)
The course of organic chemical evolution preceding the emergence of life on earth is discussed based on evidence of processes occurring in interstellar space, the solar system and the primitive earth. Following a brief review of the equilibrium condensation model for the origin and evolution of the solar system, consideration is given to the nature and organic chemistry of interstellar clouds, comets, Jupiter, meteorites, Venus and Mars, and the prebiotic earth. Major issues to be resolved in the study of organic chemical evolution on earth are identified regarding condensation and accretion in the solar nebula, early geological evolution, the origin and evolution of the atmosphere, organic production rates, organic-inorganic interactions, environmental fluctuations, phase separation and molecular selectivity.
Chang, S.
Microfluidic chemical analysis systems.
The field of microfluidics has exploded in the past decade, particularly in the area of chemical and biochemical analysis systems. Borrowing technology from the solid-state electronics industry and the production of microprocessor chips, researchers working with glass, silicon, and polymer substrates have fabricated macroscale laboratory components in miniaturized formats. These devices pump nanoliter volumes of liquid through micrometer-scale channels and perform complex chemical reactions and separations. The detection of reaction products is typically done fluorescently with off-chip optical components, and the analysis time from start to finish can be significantly shorter than that of conventional techniques. In this review we describe these microfluidic analysis systems, from the original continuous flow systems relying on electroosmotic pumping for liquid motion to the large diversity of microarray chips currently in use to the newer droplet-based devices and segmented flow systems. Although not currently widespread, microfluidic systems have the potential to become ubiquitous. PMID:22432622
Livak-Dahl, Eric; Sinn, Irene; Burns, Mark
NASA Technical Reports Server (NTRS)
The aerospace industry has long been perceived as the domain of both physicists and mechanical engineers. This perception has endured even though the primary method of providing the thrust necessary to launch a rocket into space is chemical in nature. The chemical engineering and chemistry personnel behind the systems that provide access to space have labored in the shadows of the physicists and mechanical engineers. As exploration into the cosmos moves farther away from Earth, there is a very distinct need for new chemical processes to help provide the means for advanced space exploration. The state of the art in launch systems uses chemical propulsion systems, primarily liquid hydrogen and liquid oxygen, to provide the energy necessary to achieve orbit. As we move away from Earth, there are additional options for propulsion. Unfortunately, few of these options can compare to the speed or ease of use provided by the chemical propulsion agents. It is with great care and significant cost that gaseous compounds such as hydrogen and oxygen are liquefied and become dense enough to use for rocket fuel. These low-temperature liquids fall within a specialty area known as cryogenics. Cryogenics, the science and art of producing cold operating conditions for use on Earth, in orbit, or on some other nonterrestrial body, has become increasingly important to our ability to travel within our solar system. The production of cryogenic fuels and the long-term storage of these fluids are necessary for travel. As our explorations move farther away from Earth, we need to address how to produce the necessary fuels to make a round-trip. The cost and the size of these expeditions are extreme at best. If we take everything necessary for our survival for the round-trip, we invalidate any chance of travel in the near future. As with the early explorers on Earth, we need to harvest much of our energy and our life support from the celestial bodies. The in situ production of these energy sources is paramount to success. We are currently working on several processes to produce the propellants that would allow us to visit and explore the surface of Mars. The capabilities currently at our disposal for launching and delivering equipment to another planet or satellite dictate that the size and scale of any hardware must be extremely small. The miniaturization of the processes needed to prepare the in situ propellants and life support commodities is a real challenge. Chemical engineers are faced with the prospect of reproducing an entire production facility in miniature so the complex can be lifted into space and delivered to our destination. Another area that does not normally concern chemical engineers is the extreme physical aspects payloads are subjected to with the launch of a spacecraft. Extreme accelerations followed by the sudden loss of nearly all gravitational forces are well outside normal equipment design conditions. If the equipment cannot survive the overall trip, then it obviously will not be able to yield the needed products upon arrival. These launch constraints must be taken into account. Finally, we must consider both the effectiveness and efficiencies of the processes. A facility located on the Moon or Mars will not have an unlimited supply of power or other ancillary utilities. For a Mars expedition, the available electric power is severely limited. The design of both the processes and the equipment must be considered. With these constraints in mind, only the most efficient designs will be viable. Cryogenics, in situ resource utilization, miniaturization, launchability, and power/process efficiencies are only a few of the areas that chemical engineers provide support and expertise for the exploration of space.
Lobmeyer, Dennis A.; Meneghelli, Barry; Steinrock, Todd (Technical Monitor)
Physical and chemical weathering
NASA Astrophysics Data System (ADS)
Physical and chemical weathering processes that might be important on Mars are reviewed, and the limited observations, including relevant Viking results and laboratory simulations, are summarized. Physical weathering may have included rock splitting through growth of ice, salt or secondary silicate crystals in voids. Chemical weathering probably involved reactions of minerals with water, oxygen, and carbon dioxide, although predicted products vary sensitively with the abundance and physical form postulated for the water. On the basis of kinetics data for hydration of rock glass on earth, the fate of weathering-rind formation on glass-bearing Martian volcanic rocks is tentatively estimated to have been on the order of 0.1 to 4.5 cm/Gyr; lower rates would be expected for crystalline rocks.
Gooding, James L.; Arvidson, Raymond E.; Zolotov, Mikhail Iu.
Chemical Modification of Polysaccharides
This review covers methods for modifying the structures of polysaccharides. The introduction of hydrophobic, acidic, basic, or other functionality into polysaccharide structures can alter the properties of materials based on these substances. The development of chemical methods to achieve this aim is an ongoing area of research that is expected to become more important as the emphasis on using renewable starting materials and sustainable processes increases in the future. The methods covered in this review include ester and ether formation using saccharide oxygen nucleophiles, including enzymatic reactions and aspects of regioselectivity; the introduction of heteroatomic nucleophiles into polysaccharide chains; the oxidation of polysaccharides, including oxidative glycol cleavage, chemical oxidation of primary alcohols to carboxylic acids, and enzymatic oxidation of primary alcohols to aldehydes; reactions of uronic-acid-based polysaccharides; nucleophilic reactions of the amines of chitosan; and the formation of unsaturated polysaccharide derivatives.
Cumpstey, Ian
NASA Astrophysics Data System (ADS)
We study chemical aging in ``Cooee bitumen'' using molecular dynamic simulations. This model bitumen is composed of four realistic molecule types: saturated hydrocarbon, resinous oil, resin, and asphaltene. The aging reaction is modelled by the chemical reaction: ``2 resins --> 1 asphaltene.'' Molecular dynamic simulations of four bitumen compositions, obtained by a repeated application of the aging reaction, are performed. The stress autocorrelation function, the fluid structure, the rotational dynamics of the plane aromatic molecules, and the diffusivity of each molecule are determined for the four different compositions. The aging reaction causes a significant dynamics slowdown, which is correlated to the aggregation of asphaltene molecules in larger and dynamically slower nanoaggregates. Finally, a detailed description of the role of each molecule types in the aggregation and aging processes is given.
Lemarchand, Claire A.; Schr�der, Thomas B.; Dyre, Jeppe C.; Hansen, Jesper S.
Environmental and chemical carcinogenesis.
People are continuously exposed exogenously to varying amounts of chemicals that have been shown to have carcinogenic or mutagenic properties in experimental systems. Exposure can occur exogenously when these agents are present in food, air or water, and also endogenously when they are products of metabolism or pathophysiologic states such as inflammation. It has been estimated that exposure to environmental chemical carcinogens may contribute significantly to the causation of a sizable fraction, perhaps a majority, of human cancers, when exposures are related to "life-style" factors such as diet, tobacco use, etc. This chapter summarizes several aspects of environmental chemical carcinogenesis that have been extensively studied and illustrates the power of mechanistic investigation combined with molecular epidemiologic approaches in establishing causative linkages between environmental exposures and increased cancer risks. A causative relationship between exposure to aflatoxin, a strongly carcinogenic mold-produced contaminant of dietary staples in Asia and Africa, and elevated risk for primary liver cancer has been demonstrated through the application of well-validated biomarkers in molecular epidemiology. These studies have also identified a striking synergistic interaction between aflatoxin and hepatitis B virus infection in elevating liver cancer risk. Use of tobacco products provides a clear example of cancer causation by a life-style factor involving carcinogen exposure. Tobacco carcinogens and their DNA adducts are central to cancer induction by tobacco products, and the contribution of specific tobacco carcinogens (e.g. PAH and NNK) to tobacco-induced lung cancer, can be evaluated by a weight of evidence approach. Factors considered include presence in tobacco products, carcinogenicity in laboratory animals, human uptake, metabolism and adduct formation, possible role in causing molecular changes in oncogenes or suppressor genes, and other relevant data. This approach can be applied to evaluation of other environmental carcinogens, and the evaluations would be markedly facilitated by prospective epidemiologic studies incorporating phenotypic carcinogen-specific biomarkers. Heterocyclic amines represent an important class of carcinogens in foods. They are mutagens and carcinogens at numerous organ sites in experimental animals, are produced when meats are heated above 180 degrees C for long periods. Four of these compounds can consistently be identified in well-done meat products from the North American diet, and although a causal linkage has not been established, a majority of epidemiology studies have linked consumption of well-done meat products to cancer of the colon, breast and stomach. Studies employing molecular biomarkers suggest that individuals may differ in their susceptibility to these carcinogens, and genetic polymorphisms may contribute to this variability. Heterocyclic amines, like most other chemical carcinogens, are not carcinogenic per se but must be metabolized by a family of cytochrome P450 enzymes to chemically reactive electrophiles prior to reacting with DNA to initiate a carcinogenic response. These same cytochrome P450 enzymes--as well as enzymes that act on the metabolic products of the cytochromes P450 (e.g. glucuronyl transferase, glutathione S-transferase and others)--also metabolize chemicals by inactivation pathways, and the relative amounts of activation and detoxification will determine whether a chemical is carcinogenic. Because both genetic and environmental factors influence the levels of enzymes that metabolically activate and detoxify chemicals, they can also influence carcinogenic risk. Many of the phenotypes of cancer cells can be the result of mutations, i.e., changes in the nucleotide sequence of DNA that accumulate as tumors progress. These can arise as a result of DNA damage or by the incorporation of non-complementary nucleotides during DNA synthetic processes. Based upon the disparity between the infrequency of spontaneous mutations and the large numbers of
Wogan, Gerald N; Hecht, Stephen S; Felton, James S; Conney, Allan H; Loeb, Lawrence A
Background, aim, and scope��Improving the parameterization of processes in the atmospheric boundary layer (ABL) and surface layer, in air quality and\\u000a chemical transport models. To do so, an asymmetrical, convective, non-local scheme, with varying upward mixing rates is combined\\u000a with the non-local, turbulent, kinetic energy scheme for vertical diffusion (COM). For designing it, a function depending\\u000a on the dimensionless height
Dragutin T. Mihailovic; Kiran Alapaty; Zorica Podrascanin
Chemical vapor deposition sciences
Chemical vapor deposition (CVD) is a widely used method for depositing thin films of a variety of materials. Applications of CVD range from the fabrication of microelectronic devices to the deposition of protective coatings. New CVD processes are increasingly complex, with stringent requirements that make it more difficult to commercialize them in a timely fashion. However, a clear understanding of the fundamental science underlying a CVD process, as expressed through computer models, can substantially shorten the time required for reactor and process development. Research scientists at Sandia use a wide range of experimental and theoretical techniques for investigating the science of CVD. Experimental tools include optical probes for gas-phase and surface processes, a range of surface analytic techniques, molecular beam methods for gas/surface kinetics, flow visualization techniques and state-of-the-art crystal growth reactors. The theoretical strategy uses a structured approach to describe the coupled gas-phase and gas-surface chemistry, fluid dynamics, heat and mass transfer of a CVD process. The software used to describe chemical reaction mechanisms is easily adapted to codes that model a variety of reactor geometries. Carefully chosen experiments provide critical information on the chemical species, gas temperatures and flows that are necessary for model development and validation. This brochure provides basic information on Sandia`s capabilities in the physical and chemical sciences of CVD and related materials processing technologies. It contains a brief description of the major scientific and technical capabilities of the CVD staff and facilities, and a brief discussion of the approach that the staff uses to advance the scientific understanding of CVD processes.
Continuous filament ceramic composites are enabling new, high temperature structural applications. Chemical vapor infiltration methods for producing these composites are being studied, with the complexity of filament weaves and deposition chemistry merged with standard heat and mass transport relationships. Silicon carbide-based materials are, by far, the most advanced, and are already being used in aerospace applications. This paper will address the state-of-the-art of the technology and outline current issues.
Besmann, T.M.; Stinton, D.P.; Lowden, R.A.
Continuous filament ceramic composites are enabling new, high temperature structural applications. Chemical vapor infiltration methods for producing these composites are being studied, with the complexity of filament weaves and deposition chemistry merged with standard heat and mass transport relationships. Silicon carbide-based materials are, by far, the most advanced, and are already being used in aerospace applications. This paper will address the state-of-the-art of the technology and outline current issues.
Besmann, T.M.; Stinton, D.P.; Lowden, R.A.
NASA Technical Reports Server (NTRS)
Primers employed in bonding together the various material interfaces in a photovoltaic module are being developed. The approach develops interfacial adhesion by generating actual chemical bonds between the various materials bonded together. The current status of the program is described along with the progress toward developing two general purpose primers for ethylene vinyl acetate (EVA), one for glass and metals, and another for plastic films.
Plueddemann, E.
NSDL National Science Digital Library
Stephen Lower, a retired professor at Simon Fraser University, created this expansive and instructive website as a supplement to formal chemistry education for undergraduate students. Visitors will find in-depth descriptions along with several diagrams dealing with chemical bonding issues including their properties, shared-electron covalent bonds, hybrid orbitals, coordination complexes, and metals and semiconductors. General chemistry students looking for assistance should visit this well-developed educational site.
Lower, Stephen
NSDL National Science Digital Library
The Society of Chemical Industry is "an international association of about 6000 members aimed at furthering applied chemistry." One of the highlights of its web site is its publication section, where, under "electronic publications," readers can find updated daily news, jobs and meetings listings on chemistry, pharmaceuticals, biotechnology, and the environment. The SCI home page also carries information about the organization, as well as details about its over 35 subject and geographical groups and their meeting schedules.
Chemical measurements in Drosophila
The fruit fly, Drosophila melanogaster, has been extensively used as a model organism in genetics research and has significantly contributed to understanding molecular, cellular and evolutionary aspects of human behavior. Recently, research has focused on developing analytical methods to obtain highly sensitive chemical quantification along with spatiotemporal information from Drosophila melanogaster. We review a number of these advances in capillary electrophoresis, high-performance liquid chromatography, mass spectrometry and technologies involving intact organisms, including in vivo electrochemistry.
Makos, Monique A.; Kuklinski, Nicholas J.; Berglund, E. Carina; Heien, Michael L.; Ewing, Andrew G.
NASA Technical Reports Server (NTRS)
A chemical sensing apparatus and method for the detection of sub parts-per-trillion concentrations of molecules in a sample by optimizing electron utilization in the formation of negative ions is provided. A variety of media may be sampled including air, seawater, dry sediment, or undersea sediment. An electrostatic mirror is used to reduce the kinetic energy of an electron beam to zero or near-zero kinetic energy.
Darrach, Murray R. (Inventor); Chutjian, Ara (Inventor)
Chemical Demonstrations with Consumer Chemicals: The Black and White Reaction.
ERIC Educational Resources Information Center
Describes a dramatic chemical demonstration in which chemicals that are black and white combine to produce a colorless liquid. Reactants include tincture of iodine, bleach, white vinegar, Epsom salt, vitamin C tablets, and liquid laundry starch. (DDR)
Wright, Stephen W.
Chemical emergency preparedness program: chemical profiles. Interim guidance
The document, developed by the U.S. Environmental Protection Agency (USEPA) is part of the USEPA National Air Toxics Strategy. The document is provided in support of EPA Chemical Emergency Preparedness Program (CEPP) which deals with accidental release of acutely toxic chemicals. For each acutely toxic chemical listed in the CEPP guidance document (report number PB86-155256), a chemical profile is available. A chemical profile is a collection of information on the chemical identity hazardous identity, physical/chemical characteristics, fire and explosive hazard, reactivity, health hazard, use, and precautions for handling and use of the chemical. The information is presented in the format that conforms as closely as possible to the Occupational Safety and Health Administration (OSHA) recommended format for a Material Safety Data Sheet (MSDS).
Not Available
NSDL National Science Digital Library
In March 2001, PBS aired a disturbing two-hour special hosted by Bill Moyers that explores the history of the chemical revolution of the past 50 years and how companies have long sought to withhold information from the public and their employees about the safety of many substances. The program draws on a large collection of previously secret industry documents unearthed during a ten-year lawsuit by the family of a man who died from a rare brain cancer after working at a vinyl-chloride plant. The family's lawyer eventually charged all vinyl-chloride-producing companies with conspiracy, and the discovery process brought to light hundreds of thousands of pages of documents which reveal a closely planned and well-executed campaign to limit regulation of toxic chemicals and the liability of manufacturers and to withhold important health information from all parties. A large selection of these internal documents, over 37,000 pages, is available at the Chemical Industry Archives, created by the Environmental Working Group. The site offers several essays on the archive and the industry, including a selection of some egregious examples of companies hiding or denying known health risks of their products. The archive itself may be searched by keyword with several modifiers. The documents are presented in .pdf format. This site is sure to become an extremely important resource for health activists, journalists, and the concerned public.
A new chemical detection technology has been realized that addresses DOE environmental management needs. The new technology is based on a variant of the sensitive optical absorption technique, cavity ring-down spectroscopy (CRDS). Termed evanescent-wave cavity ring-down spectroscopy (EW-CRDS), the technology employs a miniature solid-state optical resonator having an extremely high Q-factor as the sensing element, where the high-Q is achieved by using ultra-low-attenuation optical materials, ultra-smooth surfaces, and ultra-high reflectivity coatings, as well as low-diffraction-loss designs. At least one total-internal reflection (TIR) mirror is integral to the resonator permitting the concomitant evanescent wave to probe the ambient environment. Several prototypes have been designed, fabricated, characterized, and applied to chemical detection. Moreover, extensions of the sensing concept have been explored to enhance selectivity, sensitivity, and range of application. Operating primarily in the visible and near IR regions, the technology inherently enables remote detection by optical fiber. Producing 11 archival publications, 5 patents, 19 invited talks, 4 conference proceedings, a CRADA, and a patent-license agreement, the project has realized a new chemical detection technology providing >100 times more sensitivity than comparable technologies, while also providing practical advantages.
Andrew C. R. Pipino
NASA Technical Reports Server (NTRS)
Work during the past three years has included significant research in several areas aimed at further clarification of the aging and chemical failure mechanism of thermoplastics (PVDF or Tefzel) for pipes. Among the areas investigated were the crystallinity changes associated with both the Coflon and Tefzel after various simulated environmental exposures using X-Ray diffraction analysis. We have found that significant changes in polymer crystallinity levels occur as a function of the exposures. These crystallinity changes may have important consequences on the fracture, fatigue, tensile, and chemical resistance of the materials. We have also noted changes in the molecular weight distribution and the increased crosslinking of the Coflon material using Gel Permeation Chromatographic Analysis. Again these changes may result in variations in the mechanical and chemical properties in the material. We conducted numerous analytical studies with methods including X-ray Diffraction, Gel Permeation Chromatography, Fourier Transform Infrared Spectroscopy, and Differential Scanning Calorimetry. We investigated a plethora of aged samples of both Tefzel and Coflon that were forwarded from MERL. Pressurized tests were performed on powdered PVDF in a modified Fluid A, which we will call A-2. In this case the ethylene diamine concentration was increased to 3 percent in methanol. Coflon pipe sections and powdered Coflon were exposed in pressure cells at 1700 psi at three separate test temperatures.
Bulluck, J. W.; Rushing, R. A.
NASA Technical Reports Server (NTRS)
Work has included significant research in several areas aimed at further clarification of the aging and chemical failure mechanism of thermoplastics (PVDF or Tefzel) for pipes. Among the areas investigated were the crystallinity changes associated with both the Coflon and Tefzel after various simulated environmental exposures using X-Ray diffraction analysis. We have found that significant changes in polymer crystallinity levels occur as a function of the exposures. These crystallinity changes may have important consequences on the fracture, fatigue, tensile, and chemical resistance of the materials. We have also noted changes in the molecular weight distribution of the Coflon material using a dual detector Gel Permeation Analysis. Again these changes may result in variation in the mechanical and chemical properties in the material. We conducted numerous analytical studies with methods including X-Ray Diffraction, Gel Permeation Chromatography, Fourier Transform Infrared Spectroscopy, Thermogravimetric Analysis, and Differential Scanning Calorimetry. We investigated a number of aged samples of both Tefzel and Coflon that were forwarded from MERL. Pressurized tests were performed in a modified Fluid G, which we will call G2. In this case the ethylene diamine concentration was increased to 3 percent in methanol. Coflon pipe sections and powdered Coflon were exposed in pressure cells at 1700 psi at three separate test temperatures, 70 C, 110 C, and 130 C. The primary purpose of the pressure tests in Fluid G2 was to further elucidate the aging mechanism of PVDF degradation.
Bulluck, J. W.; Rushing, R. A.; Thornton, C. P.
NSDL National Science Digital Library
The American Chemical Society produces the weekly magazine "Chemical & Engineering News" which reports on topics ranging from business to government to education drawn from across the world of chemistry. Although much of the content on the website is password-protected for those with a subscription to the magazine, the fascinating "Multimedia" section of the website is accessible to all visitors. The "Latest Photo Galleries" section has the must see gallery "Another Kind of Landscape" from May 2, 2011, which is about a new book on environmental degradation. There are just five photos, all aerial views, that at first blush look beautiful and like works of art, but upon reading the caption, visitors will learn that the photos are of the run-off from a fertilizer plant, an aluminum producer, and a coal mine. The enlightening and interactive article from June 2007 (under "Other Multimedia") titled "The Incredible Vastness of Data lets visitors visualize the differences between chemical research conducted in 1907 and 2007. Overall, the multimedia has much to offer and warrants several return visits.
Chemical Reactions at Surfaces
Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The program this year will cover a broad range of topics, including heterogeneous catalysis and surface chemistry, surfaces in environmental chemistry and energy conversion, reactions at the liquid-solid and liquid-gas interface, electronic materials growth and surface modification, biological interfaces, and electrons and photons at surfaces. An exciting program is planned, with contributions from outstanding speakers and discussion leaders from the international scientific community. The conference provides a dynamic environment with ample time for discussion and interaction. Attendees are encouraged to present posters; the poster sessions are historically well attended and stimulate additional discussions. The conference provides an excellent opportunity for junior researchers (e.g. graduate students or postdocs) to present their work and interact with established leaders in the field.
Michael Henderson and Nancy Ryan Gray
The OPPT Chemical Fact Sheets are produced by the Office of Pollution, Prevention and Toxics to provide a brief summary of information on selected chemicals. The Fact Sheets cover each chemicals identity, production and use, environmental fate, and health and environmental effect...
Devices for collecting chemical compounds
A device for sampling chemical compounds from fixed surfaces and related methods are disclosed. The device may include a vacuum source, a chamber and a sorbent material. The device may utilize vacuum extraction to volatilize the chemical compounds from a fixed surface so that they may be sorbed by the sorbent material. The sorbent material may then be analyzed using conventional thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) instrumentation to determine presence of the chemical compounds. The methods may include detecting release and presence of one or more chemical compounds and determining the efficacy of decontamination. The device may be useful in collection and analysis of a variety of chemical compounds, such as residual chemical warfare agents, chemical attribution signatures and toxic industrial chemicals.
Scott, Jill R; Groenewold, Gary S
Meltblowns for Chemical Protective Liners.
National Technical Information Service (NTIS)
The purpose of chemical protective clothing is to shield or isolate individuals from the chemical, physical, and biological hazards that may be encountered in potentially hazardous environments, including biological hazards. When dealing with hazardous ma...
L. C. Wadsworth Y. E. Lee H. L. Schreuder-Gibson P. W. Gibson
Control in the Chemical Industry
ERIC Educational Resources Information Center
Discusses various control techniques used in chemical processes, including measuring devices, controller functions, control valves, and feedforward and feedback actions. Applications of control to a real chemical plant are exemplified. (CC)
Jones, R. G.
Marine Pollution from Offshore Chemicals.
National Technical Information Service (NTIS)
The report analyses the influencing impact on the marine environment caused by the various chemical effluents from the offshore drilling and production. The offshore chemicals used at the Statfjord and Ekofisk fields on the Norwegian Continental Shelf are...
O. Bjoerseth G. Halmoe R. Romslo T. Syvertsen
Chemical Compatibility of Cartridge Materials.
National Technical Information Service (NTIS)
This twelve month progress report deals with the chemical compatibility of semiconductor crystals grown in zero gravity. Specifically, it studies the chemical compatibility between TZM, a molybdenum alloy containing titanium and zirconium, and WC 103, a t...
R. C. Wilcox R. H. Zee
Chemical Hazards to Human Reproduction.
National Technical Information Service (NTIS)
This report is an evaluation and documentation of the current evidence for reproductive hazards of chemicals, an evaluation of the policy implications of the state of knowledge about chemical hazards to human reproduction, a review of occupational exposur...
Evapotranspiration and Its Chemical Reduction.
National Technical Information Service (NTIS)
The project consisted of a laboratory phase and a field phase. For the laboratory phase several chemicals were screened for their potential in decreasing transpiration. Because transpiration is water evaporation from the stomata of plant leaves, chemicals...
W. L. Powers G. M. Paulsen R. K. Palis L. J. Brun E. T. Kanemasu
40 CFR Table 1 to Subpart F of... - Synthetic Organic Chemical Manufacturing Industry Chemicals
Code of Federal Regulations, 2013 CFR
... false Synthetic Organic Chemical Manufacturing Industry Chemicals 1 Table 1 to...From the Synthetic Organic Chemical Manufacturing Industry Pt. 63, Subpt. F, Table...Part 63�Synthetic Organic Chemical Manufacturing Industry Chemicals Chemical...
Canadian Society for Chemical Technology
NSDL National Science Digital Library
The Canadian Society for Chemical Technology (CSCT) is dedicated to "the advancement of chemical technology, the maintenance and improvement of standards of practitioners and educators, and the continual evaluation of chemical technology in Canada." Users can learn about the Society's many activities including certifying chemical technologists and supporting student endeavors. The site features upcoming workshops and events held in Europe and North America. Visitors can learn about student and regional chapters.
Mass Transfer with Chemical Reaction.
ERIC Educational Resources Information Center
Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)
DeCoursey, W. J.
Green chemistry for chemical synthesis
Green chemistry for chemical synthesis addresses our future challenges in working with chemical processes and products by inventing novel reactions that can maximize the desired products and minimize by-products, designing new synthetic schemes and apparati that can simplify operations in chemical productions, and seeking greener solvents that are inherently environmentally and ecologically benign.
Li, Chao-Jun; Trost, Barry M.
Green chemistry for chemical synthesis.
Green chemistry for chemical synthesis addresses our future challenges in working with chemical processes and products by inventing novel reactions that can maximize the desired products and minimize by-products, designing new synthetic schemes and apparati that can simplify operations in chemical productions, and seeking greener solvents that are inherently environmentally and ecologically benign. PMID:18768813
Li, Chao-Jun; Trost, Barry M
Chemical Kinetics: Rate of Reaction
NSDL National Science Digital Library
This site offers an interactive tutorial that emphasizes graphical interpretation of chemical kinetics. The stoichiometric coefficients for a chemical equation are determined by comparing the slopes of concentration-time plots for the reactants and products. This tutorial is coupled to others to further guide the student to a better understanding of chemical kinetics.
Blauch, David N.
Modern Chemical Technology, Volume 8.
ERIC Educational Resources Information Center
This volume is one of a series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: amino acids and proteins, carbohydrates, synthetic polymers, other natural products, chemical separations�
Pecsok, Robert L.; Chapman, Kenneth
Modern Chemical Technology, Volume 5.
ERIC Educational Resources Information Center
This volume contains chapters 26-31 for the American Chemical Society (ACS) "Modern Chemical Technology" (ChemTeC) instructional material intended to prepare chemical technologists. Chapter 26 reviews oxidation and reduction, including applications in titrations with potassium permanganate and iodometry. Coordination compounds are described in the�
Pecsok, Robert L., Ed.; Chapman, Kenneth, Ed.
The chemical ecology of cyanobacteria.
This review covers the literature on the chemically mediated ecology of cyanobacteria, including ultraviolet radiation protection, feeding-deterrence, allelopathy, resource competition, and signalling. To highlight the chemical and biological diversity of this group of organisms, evolutionary and chemotaxonomical studies are presented. Several technologically relevant aspects of cyanobacterial chemical ecology are also discussed. PMID:22237837
Le�o, Pedro N; Engene, Niclas; Antunes, Agostinho; Gerwick, William H; Vasconcelos, Vitor
Stochastic Simulation of Chemical Kinetics
Stochastic chemical kinetics describes the time evolution of a well- stirred chemically reacting system in a way that takes into account the fact that molecules come in whole numbers and exhibit some degree of randomness in their dynamical behavior. Researchers are increasingly using this approach to chemical kinetics in the analysis of cellular systems in biology, where the small molecular
Daniel T. Gillespie
Graph kernels for chemical informatics
Increased availability of large repositories of chemical compounds is creating new challenges and opportunities for the application of machine learning methods to problems in computational chemistry and chemical informatics. Because chemical compounds are often represented by the graph of their covalent bonds, machine learning methods in this domain must be capable of processing graphical structures with variable size. Here we
Liva Ralaivola; Sanjay Joshua Swamidass; Hiroto Saigo; Pierre Baldi
Sensitivities of Selected Chemical Detectors.
National Technical Information Service (NTIS)
This document includes an assessment of the sensitivity of three chemical agent detectors. The Joint Chemical Agent Detector (JCAD), the Automatic Chemical Agent Detector Alarm (ACADA) and the AP2C detector made by the Proengin Corporation are the three d...
E. L. Berger
NASA Astrophysics Data System (ADS)
Improving the performance and reliability characteristics of chemical propulsion systems requires research and testing of higher-performance propellants, higher efficiency thrusters, cryogenics technology, lightweight components and advancements in propulsion system design and assessment. Propellants are being investigated to identify practical combinations with higher efficiencies and better thermal properties to reduce thermal control requirements. This includes combinations with modest increases, such as LOX-hydrazine, as well as a new evaluation of major improvements available from fluorine-bearing oxidizers. Practical ways of implementing cryogenic propulsion to further increase efficiency are also being studied. Some potential advances include small pump-fed engines, and improvements in cryocooler technology and tank pressure control. Gelled propellants will be tested to determine the practicality of letting propellants freeze at low environmental temperatures and thawing them only when required for use. The propellant tank is typically the single highest non-expendable mass in a chemical propulsion system. Lightweight tank designs, materials and methods of fabrication are being investigated. These are projected to offer a 45-50 percent decrease in tank mass, representing the potential inert system mass savings. Mission and systems analyses are being conducted to guide the technology research and set priorities for technology investment, based on estimated gains in payload and mission capabilities. This includes development of advanced assessment tools and analyses of specific missions selected from Science Missions' Directorate. The goal is to mature a suite of reliable advanced propulsion technologies that will promote more cost efficient missions through the reduction of interplanetary trip time, increased scientific payload mass fraction and longer on-station operations. This talk will review the Advanced Chemical technology development roadmap, current funded technology development work, future funding opportunities and results from on-going mission studies.
Alexander, L.
Chemically induced cosmetic alopecia.
Cosmetic causes of scarring alopecia are poorly documented. They include traction alopecia and hot-combing. Recently, another group has presented in the South London area, related to misuse of chemical hair straightening agents. Affected patients are young, female, of Afro-Caribbean origin, and typically display hair loss on the vertex of the scalp. Histology shows a pattern of fibrosis and inflammation characteristic of the physical damage seen with other cosmetic procedures. This histological pattern is distinguishable from other non-cosmetic causes of scarring alopecia. PMID:8504045
Nicholson, A G; Harland, C C; Bull, R H; Mortimer, P S; Cook, M G
Chemically rechargeable battery
NASA Technical Reports Server (NTRS)
Batteries (50) containing oxidized, discharged metal electrodes such as an iron-air battery are charged by removing and storing electrolyte in a reservoir (98), pumping fluid reductant such as formalin (aqueous formaldehyde) from a storage tank (106) into the battery in contact with the surfaces of the electrodes. After sufficient iron hydroxide has been reduced to iron, the spent reductant is drained, the electrodes rinsed with water from rinse tank (102) and then the electrolyte in the reservoir (106) is returned to the battery. The battery can be slowly electrically charged when in overnight storage but can be quickly charged in about 10 minutes by the chemical procedure of the invention.
Graf, James E. (Inventor); Rowlette, John J. (Inventor)
Chemically functionalized surface patterning.
Patterning substrates with versatile chemical functionalities from micro- to nanometer scale is a long-standing and interesting topic. This review provides an overview of a range of techniques commonly used for surface patterning. The first section briefly introduces conventional micropatterning tools, such as photolithography and microcontact printing. The second section focuses on the currently used nanolithographic techniques, for example, scanning probe lithography (SPL), and their applications in surface patterning. Their advantages and disadvantages are also demonstrated. In the last section, dip-pen nanolithography (DPN) is emphatically illustrated, with a particular stress on the patterning and applications of biomolecules. PMID:21678549
Zhou, Xiaozhu; Boey, Freddy; Huo, Fengwei; Huang, Ling; Zhang, Hua
US Patent & Trademark Office Database
A reactor comprising an inlet, an outlet, and a conically spiraling fluid flow channel coupled between the inlet and the outlet. The reactor may be an electrochemical reactor comprising a fluid flow channel that spirals about an axis, the fluid flow channel comprising an anode, a cathode across from the anode, and a membrane disposed between the anode and the cathode. The reactor may have a number of design parameters that are based upon one or more reaction species and that favor the occurrence of a reaction associated with the species. The reactor may be used for the electrolysis of water or for the production of other chemical products.
Chemical Cartography with APOGEE
NASA Astrophysics Data System (ADS)
The SDSS-III APOGEE experiment is obtaining high-resolution near-IR spectra to provide measurements of stellar parameters and chemical abundances for stars in many different regions of the Galaxy. I will discuss initial results on the spatial variations of abundances derived from APOGEE data to date. In particular, I focus on mean metallicities in the Milky Way disk over a large range of Galactocentric radius (3 Holtzman, Jon A.; Hayden, M. R.; Bovy, J.; Majewski, S.; Johnson, J.; Zasowski, G.; Girardi, L.; Allende-Prieto, C.; Garcia Perez, A.; Meszaros, S.; Nidever, D. L.; Schiavon, R. P.; Shetrone, M. D. 2014-01-01
Holtzman, Jon A.; Hayden, M. R.; Bovy, J.; Majewski, S.; Johnson, J.; Zasowski, G.; Girardi, L.; Allende-Prieto, C.; Garcia Perez, A.; Meszaros, S.; Nidever, D. L.; Schiavon, R. P.; Shetrone, M. D.
A new chemical probe determines the properties of an analyte using the light absorption of the products of a reagent/analyte reaction. The probe places a small reaction volume in contact with a large analyte volume. Analyte diffuses into the reaction volume. Reagent is selectively supplied to the reaction volume. The light absorption of the reaction in the reaction volume indicates properties of the original analyte. The probe is suitable for repeated use in remote or hostile environments. It does not require physical sampling of the analyte or result in significant regent contamination of the analyte reservoir.
Laguna, George R. (Albuquerque, NM); Peter, Frank J. (Albuquerque, NM); Butler, Michael A. (Albuquerque, NM)
Chemical Microthruster Options
NASA Technical Reports Server (NTRS)
Chemical propulsion systems with potential application to microsatellites are classified by propellant phase, i.e. gas, liquid, or solid. Four promising concepts are selected based on performance, weight, size, cost, and reliability. The selected concepts, in varying stages of development, are advanced monopropellants, tridyne(TM), electrolysis, and solid gas generator propulsion. Tridyne(TM) and electrolysis propulsion are compared vs. existing cold gas and monopropellant systems for selected microsatellite missions. Electrolysis is shown to provide a significant weight advantage over monopropellant propulsion for an orbit transfer and plane change mission. Tridyne(TM) is shown to provide a significant advantage over cold gas thrusters for orbit trimming and spacecraft separation.
DeGroot, Wim; Oleson, Steve
A new chemical probe determines the properties of an analyte using the light absorption of the products of a reagent/analyte reaction. The probe places a small reaction volume in contact with a large analyte volume. Analyte diffuses into the reaction volume. Reagent is selectively supplied to the reaction volume. The light absorption of the reaction in the reaction volume indicates properties of the original analyte. The probe is suitable for repeated use in remote or hostile environments. It does not require physical sampling of the anal