text: DSpace Collection: http://hdl.handle.net/2381/10633 2015-04-01T10:39:43Z 2015-04-01T10:39:43Z DORIS_Net: enhancing the regional impact of COPERNICUS program by setting up the European Network of Regional Contact Offices Gil, A. Bosc, C. Basoni, A. Clavée, M. Bacai, Hina Pergola, N. Monbet, P. Zolotikova, Svetlana Zepeda-Juarez, J. Antoninetti, M. Tramutoli, V. Wells, Alan Carrara, P. http://hdl.handle.net/2381/31945 2015-03-31T02:00:22Z 2015-03-30T11:29:00Z Title: DORIS_Net: enhancing the regional impact of COPERNICUS program by setting up the European Network of Regional Contact Offices Authors: Gil, A.; Bosc, C.; Basoni, A.; Clavée, M.; Bacai, Hina; Pergola, N.; Monbet, P.; Zolotikova, Svetlana; Zepeda-Juarez, J.; Antoninetti, M.; Tramutoli, V.; Wells, Alan; Carrara, P. Abstract: Despite successful technological developments, COPERNICUS, the European Earth Observation flagship program, has been showing a weak regional involvement with regards to the wide capacities and benefits it provides for the Environment and Security domains at public and private level. During the DORIS_Net project, a methodology was successfully implemented to raise regional awareness on COPERNICUS potential with the concept of a Regional Contact Offices (RCO) Network. This paper aims to describe the process of RCO's creation and certification. It also presents both benefits and challenges of management and sustainability faced by RCO in order to reach their operational goals. Finally, the paper explores the potential regional impact of RCO. 2015-03-30T11:29:00Z The substellar companion in the eclipsing white dwarf binary SDSS J141126.20+200911.1 Littlefair, S. P. Casewell, Sarah L. Parsons, S. G. Dhillon, V. S. Marsh, T. R. Gaensicke, B. T. Bloemen, S. Catalan, S. Irawati, P. Hardy, L. K. Mcallister, M. Bours, M. C. P. Richichi, A. Burleigh, Matthew R. Burningham, B. Breedt, E. Kerry, P. http://hdl.handle.net/2381/31925 2015-03-28T03:00:15Z 2015-03-27T11:25:24Z Title: The substellar companion in the eclipsing white dwarf binary SDSS J141126.20+200911.1 Authors: Littlefair, S. P.; Casewell, Sarah L.; Parsons, S. G.; Dhillon, V. S.; Marsh, T. R.; Gaensicke, B. T.; Bloemen, S.; Catalan, S.; Irawati, P.; Hardy, L. K.; Mcallister, M.; Bours, M. C. P.; Richichi, A.; Burleigh, Matthew R.; Burningham, B.; Breedt, E.; Kerry, P. Abstract: We present high time resolution SDSS-g′ and SDSS-z′ light curves of the primary eclipse in SDSS J141126.20+200911.1, together with time-resolved X-Shooter spectroscopy and near-infrared (NIR) JHKs photometry. Our observations confirm the substellar nature of the companion, making SDSS J141126.20+200911.1 the first eclipsing white dwarf/brown dwarf binary known. We measure a (white dwarf model dependent) mass and radius for the brown dwarf companion of M2 = 0.050 ± 0.002 M⊙ and R2 = 0.072 ± 0.004 M⊙, respectively. The lack of a robust detection of the companion light in the z′-band eclipse constrains the spectral type of the companion to be later than L5. Comparing the NIR photometry to the expected white dwarf flux reveals a clear Ks-band excess, suggesting a spectral type in the range L7–T1. The radius measurement is consistent with the predictions of evolutionary models, and suggests a system age in excess of 3 Gyr. The low companion mass is inconsistent with the inferred spectral type of L7–T1, instead predicting a spectral type nearer T5. This indicates that irradiation of the companion in SDSS J141126.20+200911.1 could be causing a significant temperature increase, at least on one hemisphere. Description: This article has been accepted for publication in MNRAS ©: 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. 2015-03-27T11:25:24Z Black hole feedback in the luminous quasar PDS 456 Nardini, E. Reeves, J. N. Gofford, J. Harrison, F. A. Risaliti, G. Braito, V. Costa, M. T. Matzeu, G. A. Walton, D. J. Behar, E. Boggs, S. E. Christensen, F. E. Craig, W. W. Hailey, C. J. Matt, G. Miller, J. M. O'Brien, Paul T. Stern, D. Turner, T. J. Ward, M. J. http://hdl.handle.net/2381/31921 2015-03-25T03:00:15Z 2015-03-24T15:39:54Z Title: Black hole feedback in the luminous quasar PDS 456 Authors: Nardini, E.; Reeves, J. N.; Gofford, J.; Harrison, F. A.; Risaliti, G.; Braito, V.; Costa, M. T.; Matzeu, G. A.; Walton, D. J.; Behar, E.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Hailey, C. J.; Matt, G.; Miller, J. M.; O'Brien, Paul T.; Stern, D.; Turner, T. J.; Ward, M. J. Abstract: The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband X-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10^39 W is enough to provide the feedback required by models of black hole and host galaxy co-evolution. Description: SUPPLEMENTARY MATERIALS www.sciencemag.org/content/347/6224/860/suppl/DC1 2015-03-24T15:39:54Z Multi-instrument observations of the electric and magnetic field structure of omega bands Wild, J. A. Yeoman, T. K. Eglitis, P. Opgenoorth, H. J. http://hdl.handle.net/2381/31903 2015-03-20T03:00:18Z 2015-03-19T15:19:00Z Title: Multi-instrument observations of the electric and magnetic field structure of omega bands Authors: Wild, J. A.; Yeoman, T. K.; Eglitis, P.; Opgenoorth, H. J. Abstract: High time resolution data from the CUTLASS Finland radar during the interval 01:30-03:30 UT on 11 May, 1998, are employed to characterise the ionospheric electric field due to a series of omega bands extending ~5° in latitude at a resolution of 45 km in the meridional direction and 50 km in the azimuthal direction. E-region observations from the STARE Norway VHF radar operating at a resolution of 15 km over a comparable region are also incorporated. These data are combined with ground magnetometer observations from several stations. This allows the study of the ionospheric equivalent current signatures and height integrated ionospheric conductances associated with omega bands as they propagate through the field-of-view of the CUTLASS and STARE radars. The high-time resolution and multi-point nature of the observations leads to a refinement of the previous models of omega band structure. The omega bands observed during this interval have scale sizes ~500 km and an eastward propagation velocity ~0.75 km s-1. They occur in the morning sector (~05 MLT), simultaneously with the onset/intensification of a substorm to the west during the recovery phase of a previous substorm in the Scandinavian sector. A possible mechanism for omega band formation and their relationship to the substorm phase is discussed.. 2015-03-19T15:19:00Z ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes McCrea, I. W. Lockwood, M. Moen, J. Pitout, F. Eglitis, P. Aylward, A. D. Cerisier, J. C. Thorolfssen, A. Milan, S. E. http://hdl.handle.net/2381/31902 2015-03-20T03:00:18Z 2015-03-19T14:28:27Z Title: ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes Authors: McCrea, I. W.; Lockwood, M.; Moen, J.; Pitout, F.; Eglitis, P.; Aylward, A. D.; Cerisier, J. C.; Thorolfssen, A.; Milan, S. E. Abstract: We report observations of the cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) VHF radar at Tromsø and the EISCAT Svalbard radar (ESR). We compare them with observations of the dayside auroral luminosity, as seen by meridian scanning photometers at Ny Ålesund and of HF radar backscatter, as observed by the CUTLASS radar. We study the response to an interval of about one hour when the interplanetary magnetic field (IMF), monitored by the WIND and ACE spacecraft, was southward. The cusp/cleft aurora is shown to correspond to a spatially extended region of elevated electron temperatures in the VHF radar data. Initial conditions were characterised by a northward-directed IMF and cusp/cleft aurora poleward of the ESR. A strong southward turning then occurred, causing an equatorward motion of the cusp/cleft aurora. Within the equatorward expanding, southward-IMF cusp/cleft, the ESR observed structured and elevated plasma densities and ion and electron temperatures. Cleft ion fountain upflows were seen in association with elevated ion temperatures and rapid eastward convection, consistent with the magnetic curvature force on newly opened field lines for the observed negative IMF By. Subsequently, the ESR beam remained immediately poleward of the main cusp/cleft and a sequence of poleward-moving auroral transients passed over it. After the last of these, the ESR was in the polar cap and the radar observations were characterised by extremely low ionospheric densities and downward field-aligned flows. The IMF then turned northward again and the auroral oval contracted such that the ESR moved back into the cusp/cleft region. For the poleward-retreating, northward-IMF cusp/cleft, the convection flows were slower, upflows were weaker and the electron density and temperature enhancements were less structured. Following the northward turning, the bands of high electron temperature and cusp/cleft aurora bifurcated, consistent with both subsolar and lobe reconnection taking place simultaneously. The present paper describes the large-scale behaviour of the ionosphere during this interval, as observed by a powerful combination of instruments. Two companion papers, by Lockwood et al. (2000) and Thorolfsson et al. (2000), both in this issue, describe the detailed behaviour of the poleward-moving transients observed during the interval of southward Bz, and explain their morphology in the context of previous theoretical work. 2015-03-19T14:28:27Z Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events Lockwood, M. McCrea, I. W. Milan, Stephen E. Moen, J. Cerisier, J. C. Thorolfsson, A. http://hdl.handle.net/2381/31901 2015-03-19T13:56:12Z 2015-03-19T13:55:33Z Title: Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events Authors: Lockwood, M.; McCrea, I. W.; Milan, Stephen E.; Moen, J.; Cerisier, J. C.; Thorolfsson, A. Abstract: We report high-resolution observations of the southward-IMF cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) Svalbard radar (ESR), and compare them with observations of dayside auroral luminosity, as seen at a wavelength of 630 nm by a meridian scanning photometer at Ny Ålesund, and of plasma flows, as seen by the CUTLASS (co-operative UK twin location auroral sounding system) Finland HF radar. The optical data reveal a series of poleward-moving transient red-line (630 nm) enhancements, events that have been associated with bursts in the rate of magnetopause reconnection generating new open flux. The combined observations at this time have strong similarities to predictions of the effects of soft electron precipitation modulated by pulsed reconnection, as made by Davis and Lockwood (1996); however, the effects of rapid zonal flow in the ionosphere, caused by the magnetic curvature force on the newly opened field lines, are found to be a significant additional factor. In particular, it is shown how enhanced plasma loss rates induced by the rapid convection can explain two outstanding anomalies of the 630 nm transients, namely how minima in luminosity form between the poleward-moving events and how events can re-brighten as they move poleward. The observations show how cusp/cleft aurora and transient poleward-moving auroral forms appear in the ESR data and the conditions which cause enhanced 630 nm emission in the transients: they are an important first step in enabling the ESR to identify these features away from the winter solstice when supporting auroral observations are not available. 2015-03-19T13:55:33Z Simultaneous optical and radar signatures of poleward-moving auroral forms Thorolfsson, A. Cerisier, J. C. Lockwood, M. Sandholt, P. E. Senior, C. Lester, Mark http://hdl.handle.net/2381/31900 2015-03-20T03:00:19Z 2015-03-19T13:50:18Z Title: Simultaneous optical and radar signatures of poleward-moving auroral forms Authors: Thorolfsson, A.; Cerisier, J. C.; Lockwood, M.; Sandholt, P. E.; Senior, C.; Lester, Mark Abstract: Dayside poleward moving auroral forms (PMAFs) were detected between 06:30 and 07:00 UT on December 16, 1998, by the meridian scanning photometer and the all-sky camera at Ny Ålesund, Svalbard. Simultaneous SuperDARN HF radar measurements permitted the study of the associated ionospheric velocity pattern. A good general agreement is observed between the location and movement of velocity enhancements (flow channels) and the PMAFs. Clear signatures of equatorward flow were detected in the vicinity of PMAFs. This flow is believed to be the signature of a return flow outside the reconnected flux tube, as predicted by the Southwood model. The simulated signatures of this model reproduce globally the measured signatures, and differences with the experimental data can be explained by the simplifications of the model. Proposed schemes of the flow modification due to the presence of several flow channels and the modification of cusp and region 1 field-aligned currents at the time of sporadic reconnection events are shown to fit well with the observations. 2015-03-19T13:50:18Z Combined CUTLASS, EISCAT and ESR observations of ionospheric plasma flows at the onset of an isolated substorm Yeoman, T. K. Davies, J. A. Wade, N. M. Provan, G. Milan, Stephen E. http://hdl.handle.net/2381/31899 2015-03-20T03:00:19Z 2015-03-19T13:45:09Z Title: Combined CUTLASS, EISCAT and ESR observations of ionospheric plasma flows at the onset of an isolated substorm Authors: Yeoman, T. K.; Davies, J. A.; Wade, N. M.; Provan, G.; Milan, Stephen E. Abstract: On August 21st 1998, a sharp southward turning of the IMF, following on from a 20 h period of northward directed magnetic field, resulted in an isolated substorm over northern Scandinavia and Svalbard. A combination of high time resolution and large spatial scale measurements from an array of coherent scatter and incoherent scatter ionospheric radars, ground magnetometers and the Polar UVI imager has allowed the electrodynamics of the impulsive substorm electrojet region during its first few minutes of evolution at the expansion phase onset to be studied in great detail. At the expansion phase onset the substorm onset region is characterised by a strong enhancement of the electron temperature and UV aurora. This poleward expanding auroral structure moves initially at 0.9 km s-1 poleward, finally reaching a latitude of 72.5°. The optical signature expands rapidly westwards at ~6 km s-1, whilst the eastward edge also expands eastward at ~0.6 km s-1. Typical flows of 600 m s-1 and conductances of 2 S were measured before the auroral activation, which rapidly changed to ~100 m s-1 and 10-20 S respectively at activation. The initial flow response to the substorm expansion phase onset is a flow suppression, observed up to some 300 km poleward of the initial region of auroral luminosity, imposed over a time scale of less than 10 s. The high conductivity region of the electrojet acts as an obstacle to the flow, resulting in a region of low-electric field, but also low conductivity poleward of the high-conductivity region. Rapid flows are observed at the edge of the high-conductivity region, and subsequently the high flow region develops, flowing around the expanding auroral feature in a direction determined by the flow pattern prevailing before the substorm intensification. The enhanced electron temperatures associated with the substorm-disturbed region extended some 2° further poleward than the UV auroral signature associated with it. 2015-03-19T13:45:09Z Subhaloes gone Notts: subhaloes as tracers of the dark matter halo shape Hoffmann, K. Planelles, S. Gaztañaga, E. Knebe, A. Pearce, F. R. Lux, H. Onions, J. Muldrew, Stuart I. Elahi, P. Behroozi, P. Ascasibar, Y. Han, J. Maciejewski, M. Merchan, M. E. Neyrinck, M. Ruiz, A. N. Sgro, M. A. http://hdl.handle.net/2381/31890 2015-03-19T03:00:16Z 2015-03-18T15:42:39Z Title: Subhaloes gone Notts: subhaloes as tracers of the dark matter halo shape Authors: Hoffmann, K.; Planelles, S.; Gaztañaga, E.; Knebe, A.; Pearce, F. R.; Lux, H.; Onions, J.; Muldrew, Stuart I.; Elahi, P.; Behroozi, P.; Ascasibar, Y.; Han, J.; Maciejewski, M.; Merchan, M. E.; Neyrinck, M.; Ruiz, A. N.; Sgro, M. A. Abstract: We study the shapes of subhalo distributions from four dark-matter-only simulations of Milky Way-type haloes. Comparing the shapes derived from the subhalo distributions at high resolution to those of the underlying dark matter fields, we find the former to be more triaxial if the analysis is restricted to massive subhaloes. For three of the four analysed haloes, the increased triaxiality of the distributions of massive subhaloes can be explained by a systematic effect caused by the low number of objects. Subhaloes of the fourth halo show indications for anisotropic accretion via their strong triaxial distribution and orbit alignment with respect to the dark matter field. These results are independent of the employed subhalo finder. Comparing the shape of the observed Milky Way satellite distribution to those of high-resolution subhalo samples from simulations, we find agreement for samples of bright satellites, but significant deviations if faint satellites are included in the analysis. These deviations might result from observational incompleteness. 2015-03-18T15:42:39Z Simultaneous observations at different altitudes of ionospheric backscatter in the eastward electrojet Milan, Stephen E. Lester, Mark http://hdl.handle.net/2381/31888 2015-03-19T03:00:21Z 2015-03-18T11:49:45Z Title: Simultaneous observations at different altitudes of ionospheric backscatter in the eastward electrojet Authors: Milan, Stephen E.; Lester, Mark Abstract: A common feature of evening near-range ionospheric backscatter in the CUTLASS Iceland radar field of view is two parallel, approximately L-shell-aligned regions of westward flow which are attributed to irregularities in the auroral eastward electrojet region of the ionosphere. These backscatter channels are separated by approximately 100–200 km in range. The orientation of the CUTLASS Iceland radar beams and the zonally aligned nature of the flow allows an approximate determination of flow angle to be made without the necessity of bistatic measurements. The two flow channels have different azimuthal variations in flow velocity and spectral width. The nearer of the two regions has two distinct spectral signatures. The eastern beams detect spectra with velocities which saturate at or near the ion-acoustic speed, and have low spectral widths (less than 100 m s–1), while the western beams detect lower velocities and higher spectral widths (above 200 m s–1). The more distant of the two channels has only one spectral signature with velocities above the ion-acoustic speed and high spectral widths. The spectral characteristics of the backscatter are consistent with E-region scatter in the nearer channel and upper-E-region or F-region scatter in the further channel. Temporal variations in the characteristics of both channels support current theories of E-region turbulent heating and previous observations of velocity-dependent backscatter cross-section. In future, observations of this nature will provide a powerful tool for the investigation of simultaneous E- and F-region irregularity generation under similar (nearly co-located or magnetically conjugate) electric field conditions. 2015-03-18T11:49:45Z Solar cycle changes to planetary wave propagation and their influence on the middle atmosphere circulation Arnold, Neil F. Robinson, Terry R. http://hdl.handle.net/2381/31887 2015-03-19T03:00:16Z 2015-03-18T11:44:21Z Title: Solar cycle changes to planetary wave propagation and their influence on the middle atmosphere circulation Authors: Arnold, Neil F.; Robinson, Terry R. Abstract: Recent observations suggest that there may be a causal relationship between solar activity and the strength of the winter Northern Hemisphere circulation in the stratosphere. A three-dimensional model of the atmosphere between 10–140 km was developed to assess the influence of solar minimum and solar maximum conditions on the propagation of planetary waves and the subsequent changes to the circulation of the stratosphere. Ultraviolet heating in the middle atmosphere was kept constant in order to emphasise the importance of non-linear dynamical coupling. A realistic thermosphere was achieved by relaxing the upper layers to the MSIS-90 empirical temperature model. In the summer hemisphere, strong radiative damping prevents significant dynamical coupling from taking place. Within the dynamically controlled winter hemisphere, small perturbations are reinforced over long periods of time, resulting in systematic changes to the stratospheric circulation. The winter vortex was significantly weakened during solar maximum and western phase of the quasi-biennial oscillation, in accordance with reported 30 mb geopotential height and total ozone measurements. 2015-03-18T11:44:21Z Misaligned gas discs around eccentric black hole binaries and implications for the final-parsec problem Aly, Hossam Dehnen, Walter Nixon, Chris King, Andrew http://hdl.handle.net/2381/31886 2015-03-19T03:00:15Z 2015-03-18T11:32:52Z Title: Misaligned gas discs around eccentric black hole binaries and implications for the final-parsec problem Authors: Aly, Hossam; Dehnen, Walter; Nixon, Chris; King, Andrew Abstract: We investigate the evolution of low mass (Md/Mb = 0.005) misaligned gaseous discs around eccentric supermassive black hole (SMBH) binaries. These are expected to form from randomly oriented accretion events on to a SMBH binary formed in a galaxy merger. When expanding the interaction terms between the binary and a circular ring to quadrupole order and averaging over the binary orbit, we expect four non-precessing disc orientations: aligned or counter-aligned with the binary, or polar orbits around the binary eccentricity vector with either sense of rotation. All other orientations precess around either of these, with the polar precession dominating for high eccentricity. These expectations are borne out by smoothed particle hydrodynamics simulations of initially misaligned viscous circumbinary discs, resulting in the formation of polar rings around highly eccentric binaries in contrast to the coplanar discs around circular binaries. Moreover, we observe disc tearing and violent interactions between differentially precessing rings in the disc significantly disrupting the disc structure and causing gas to fall on to the binary with little angular momentum. While accretion from a polar disc may not promote SMBH binary coalescence (solving the 'final-parsec problem'), ejection of this infalling low-angular momentum material via gravitational slingshot is a possible mechanism to reduce the binary separation. Moreover, this process acts on dynamical rather than viscous time-scales, and so is much faster. 2015-03-18T11:32:52Z A statistical study of diurnal, seasonal and solar cycle variations of F-region and topside auroral upflows observed by EISCAT between 1984 and 1996 Foster, C. Lester, Mark Davies, J. A. http://hdl.handle.net/2381/31885 2015-03-19T03:00:23Z 2015-03-18T11:26:39Z Title: A statistical study of diurnal, seasonal and solar cycle variations of F-region and topside auroral upflows observed by EISCAT between 1984 and 1996 Authors: Foster, C.; Lester, Mark; Davies, J. A. Abstract: A statistical analysis of F-region and topside auroral ion upflow events is presented. The study is based on observations from EISCAT Common Programmes (CP) 1 and 2 made between 1984 and 1996, and Common Programme 7 observations taken between 1990 and 1995. The occurrence frequency of ion upflow events (IUEs) is examined over the altitude range 200 to 500 km, using field-aligned observations from CP-1 and CP-2. The study is extended in altitude with vertical measurements from CP-7. Ion upflow events were identified by consideration of both velocity and flux, with threshold values of 100 m s–1 and 1013 m–2 s–1, respectively. The frequency of occurrence of IUEs is seen to increase with increasing altitude. Further analysis of the field-aligned observations reveals that the number and nature of ion upflow events vary diurnally and with season and solar activity. In particular, the diurnal distribution of upflows is strongly dependent on solar cycle. Furthermore, events identified by the velocity selection criterion dominate at solar minimum, whilst events identified by the upward field-aligned flux criterion dominated at solar maximum. The study also provides a quantitative estimate of the proportion of upflows that are associated with enhanced plasma temperature. Between 50 and 60% of upflows are simultaneous with enhanced ion temperature, and approximately 80% of events are associated with either increased F-region ion or electron temperatures. 2015-03-18T11:26:39Z A comparison of EISCAT and HF Doppler observations of a ULF wave Wright, D. M. Yeoman, Tim K. Davies, J. A. http://hdl.handle.net/2381/31884 2015-03-19T03:00:23Z 2015-03-18T11:20:23Z Title: A comparison of EISCAT and HF Doppler observations of a ULF wave Authors: Wright, D. M.; Yeoman, Tim K.; Davies, J. A. Abstract: Since the middle of 1995, an HF Doppler sounder has been running almost continuously in northern Norway, with the receiver at Ramfjordmoen and the transmitter at Seljelvnes. Concurrent operation of the EISCAT UHF radar in common programme (CP-1) mode has made it possible to study the ionospheric signature of a magnetospheric ULF wave. These are the first results of such wave signatures observed simultaneously in both instruments. It has been demonstrated that the observed Doppler signature was mainly due to the vertical bulk motion of the ionosphere caused by the electric field perturbation of the ULF wave and the first direct observational confirmation of a numerical simulation has been achieved. The wave, which was Alfvénic nature, was detected by the instruments 8° equatorward of the broad resonance region. The implications for the deduced wave modes in the ionosphere and the mechanism producing the HF Doppler variations are discussed. 2015-03-18T11:20:23Z Solving the Puzzle of Subhalo Spins Wang, Y. Lin, W. Pearce, F. Lux, H. Muldrew, Stuart I. Onions, J. http://hdl.handle.net/2381/31882 2015-03-18T03:00:13Z 2015-03-17T14:53:42Z Title: Solving the Puzzle of Subhalo Spins Authors: Wang, Y.; Lin, W.; Pearce, F.; Lux, H.; Muldrew, Stuart I.; Onions, J. Abstract: Investigating the spin parameter distribution of subhalos in two high-resolution isolated halo simulations, recent work by Onions et al. suggested that typical subhalo spins are consistently lower than the spin distribution found for field halos. To further examine this puzzle, we have analyzed simulations of a cosmological volume with sufficient resolution to resolve a significant subhalo population. We confirm the result of Onions et al. and show that the typical spin of a subhalo decreases with decreasing mass and increasing proximity to the host halo center. We interpret this as the growing influence of tidal stripping in removing the outer layers, and hence the higher angular momentum particles, of the subhalos as they move within the host potential. Investigating the redshift dependence of this effect, we find that the typical subhalo spin is smaller with decreasing redshift. This indicates a temporal evolution, as expected in the tidal stripping scenario. 2015-03-17T14:53:42Z Interpreting broad emission-line variations - I. Factors influencing the emission-line response Goad, Michael R. Korista, K. T. http://hdl.handle.net/2381/31867 2015-03-14T02:02:46Z 2015-03-13T16:53:01Z Title: Interpreting broad emission-line variations - I. Factors influencing the emission-line response Authors: Goad, Michael R.; Korista, K. T. Abstract: We investigate the sensitivity of the measured broad emission-line responsivity dlog fline/dlog fcont to continuum variations in the context of straw-man broad emission-line region (BLR) geometries of varying size with fixed BLR boundaries, and for which the intrinsic emission-line responsivity is known a priori. We find for a generic emission line that the measured responsivity ηeff, delay and maximum of the cross-correlation function are correlated for characteristic continuum variability time-scales Tchar less than the maximum delay for that line τmax(line) for a particular choice of BLR geometry and observer orientation. The above correlations are manifestations of geometric dilution arising from reverberation effects within the spatially extended BLR. When present, geometric dilution reduces the measured responsivity, delay and maximum of the cross-correlation function. Conversely, geometric dilution is minimized if Tchar ≥ τmax(line). We also find that the measured responsivity and delay show a strong dependence on light-curve duration, with shorter campaigns resulting in smaller than expected values, and only a weak dependence on sampling rate (for irregularly sampled data). The observed strong negative correlation between continuum level and line responsivity found in previous studies cannot be explained by differences in the sampling pattern, light-curve duration or in terms of purely geometrical effects. To explain this and to satisfy the observed positive correlation between continuum luminosity and BLR size in an individual source, the responsivity-weighted radius must increase with increasing continuum luminosity. For a BLR with fixed inner and outer boundaries this requires radial surface emissivity distributions which deviate significantly from a simple power law, and in such a way that the intrinsic emission-line responsivity increases towards larger BLR radii, in line with photoionization calculations. Description: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014, The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. 2015-03-13T16:53:01Z Dayside reconnection under IMF By dominated conditions: the formation and movement of bending arcs Carter, J. A. Milan, S. E. Fear, R. C. Kullen, A. Hairston, M. R. http://hdl.handle.net/2381/31835 2015-03-11T02:02:03Z 2015-03-10T14:21:28Z Title: Dayside reconnection under IMF By dominated conditions: the formation and movement of bending arcs Authors: Carter, J. A.; Milan, S. E.; Fear, R. C.; Kullen, A.; Hairston, M. R. Editors: Kepko, L. Abstract: Based upon a survey of global auroral images collected by the Polar UVI instrument, Kullen et al. [2002] subdivided polar cap auroral arcs into a number of categories, including that of 'bending' arcs. We are concerned with those bending arcs that appear as a bifurcation of the dayside auroral oval, and which subsequently form a spur intruding into the polar cap. Once formed the spur moves polewards and antisunwards over the lifetime of the arc. We propose that dayside bending arcs are ionospheric signatures of pulses of dayside reconnection, and are therefore part of a group of transient phenomena associated with flux transfer events. We observe the formation and subsequent motion of a bending arc across the polar cap during a 30 minute interval on 8 January 1999, and we show that this example is consistent with the proposed model. We quantify the motion of the arc, and find it to be commensurate with the convection flows observed by both ground-based radar observations and space-based particle flow measurements. In addition, precipitating particles coincident with the arc appear to occur along open field lines, lending further support to the model. Description: AGU allows authors to deposit their journal articles if the version is the final published citable version of record, the AGU copyright statement is clearly visible on the posting, and the posting is made 6 months after official publication by the AGU. http://publications.agu.org/author-resource-center/usage-permissions/#repository American Geophysical Union 2015-03-10T14:21:28Z Total Electron Content in the martian atmosphere: a critical assessment of the Mars Express MARSIS datasets Sánchez-Cano, B. Morgan, D. D. Witasse, O. Radicella, S. M. Herraiz, M. Orosei, R. Cartacci, M. Cicchetti, A. Noschese, R. Kofman, W. Grima, C. Mouginot, J. Gurnett, D. A. Lester, M. Blelly, P-L. Opgenoorth, H. Quinsac, G. http://hdl.handle.net/2381/31761 2015-03-05T02:02:28Z 2015-03-04T15:43:09Z Title: Total Electron Content in the martian atmosphere: a critical assessment of the Mars Express MARSIS datasets Authors: Sánchez-Cano, B.; Morgan, D. D.; Witasse, O.; Radicella, S. M.; Herraiz, M.; Orosei, R.; Cartacci, M.; Cicchetti, A.; Noschese, R.; Kofman, W.; Grima, C.; Mouginot, J.; Gurnett, D. A.; Lester, M.; Blelly, P-L.; Opgenoorth, H.; Quinsac, G. Editors: Liemohn, M Abstract: The total electron content (TEC) is one of the most useful parameters to evaluate the behavior of the martian ionosphere because it contains information on the total amount of free electrons, the main component of the martian ionospheric plasma. The Mars Express MARSIS radar is able to derive TEC from both of its operations modes: (1) the active ionospheric sounding (AIS) mode, and (2) the subsurface mode. TEC estimates from the subsurface sounding mode can be computed from the same raw data independently using different algorithms, which should yield similar results. Significant differences on the dayside, however, have been found from two of the algorithms. Moreover, both algorithms seem also to disagree with the TEC results from the AIS mode. This paper gives a critical, quantitative and independent assessment of these discrepancies, and indicates the possible uncertainty of these databases. In addition, a comparison between the results given by the empirical model of the martian ionosphere developed by Sánchez-Cano et al. (2013) and the different datasets has been performed. The main result is that for solar zenith angles higher than 75 degrees, where the maximum plasma frequency is typically small compared with the radar frequencies, the two subsurface algorithms can be confidently used. For solar zenith angles less than 75 degrees, where the maximum plasma frequency is very close to the radar frequencies, both algorithms suffer limitations. Nevertheless, despite the solar zenith angle restrictions, the dayside TEC of one of the two algorithms is consistent with the modelled TEC. Description: Publisher's version/PDF must be used in Institutional Repository 6 months after publication. 2015-03-04T15:43:09Z Extracting organic matter on Mars: A comparison of methods involving subcritical water, surfactant solutions and organic solvents Luong, D. Court, R. W. Sephton, M. A. Sims, Mark R. Cullen, D. C. http://hdl.handle.net/2381/31743 2015-02-25T02:02:15Z 2015-02-24T15:57:28Z Title: Extracting organic matter on Mars: A comparison of methods involving subcritical water, surfactant solutions and organic solvents Authors: Luong, D.; Court, R. W.; Sephton, M. A.; Sims, Mark R.; Cullen, D. C. Abstract: The first step in many life detection protocols on Mars involves attempts to extract or isolate organic matter from its mineral matrix. A number of extraction options are available and include heat and solvent assisted methods. Recent operations on Mars indicate that heating samples can cause the loss or obfuscation of organic signals from target materials, raising the importance of solvent-based systems for future missions. Several solvent types are available (e.g. organic solvents, surfactant based solvents and subcritical water extraction) but a comparison of their efficiencies in Mars relevant materials is missing. We have spiked the well characterised Mars analogue material JSC Mars-1 with a number of representative organic standards. Extraction of the spiked JSC Mars-1 with the three solvent methods provides insights into the relative efficiency of these methods and indicates how they may be used on future Mars missions. 2015-02-24T15:57:28Z Searching for life on mars: Degradation of surfactant solutions used in organic extraction experiments Court, R. W. Sephton, M. A. Sims, Mark R. Cullen, D. C. http://hdl.handle.net/2381/31725 2015-02-21T02:03:57Z 2015-02-20T10:22:58Z Title: Searching for life on mars: Degradation of surfactant solutions used in organic extraction experiments Authors: Court, R. W.; Sephton, M. A.; Sims, Mark R.; Cullen, D. C. Abstract: Life-detection instruments on future Mars missions may use surfactant solutions to extract organic matter from samples of martian rocks. The thermal and radiation environments of space and Mars are capable of degrading these solutions, thereby reducing their ability to dissolve organic species. Successful extraction and detection of biosignatures on Mars requires an understanding of how degradation in extraterrestrial environments can affect surfactant performance. We exposed solutions of the surfactants polysorbate 80 (PS80), Zonyl FS-300, and poly[dimethylsiloxane-co-[3-(2-(2-hydroxyethoxy)ethoxy)propyl]methylsiloxane] (PDMSHEPMS) to elevated radiation and heat levels, combined with prolonged storage. Degradation was investigated by measuring changes in pH and electrical conductivity and by using the degraded solutions to extract a suite of organic compounds spiked onto grains of the martian soil simulant JSC Mars-1. Results indicate that the proton fluences expected during a mission to Mars do not cause significant degradation of surfactant compounds. Solutions of PS80 or PDMSHEPMS stored at-20°C are able to extract the spiked standards with acceptable recovery efficiencies. Extraction efficiencies for spiked standards decrease progressively with increasing temperature, and prolonged storage at 60°C renders the surfactant solutions ineffective. Neither the presence of ascorbic acid nor the choice of solvent unequivocally alters the efficiency of extraction of the spiked standards. Since degradation of polysorbates has the potential to produce organic compounds that could be mistaken for indigenous martian organic matter, the polysiloxane PDMSHEPMS may be a superior choice of surfactant for the exploration of Mars. 2015-02-20T10:22:58Z Diagenesis and Clay Mineral Formation at Gale Crater, Mars Bridges, JC Schwenzer, S. P. Leveille, R. Westall, F. Wiens, R. C. Mangold, N. Bristow, T. Edwards, P. Berger, G. http://hdl.handle.net/2381/31724 2015-02-21T02:03:56Z 2015-02-20T09:59:48Z Title: Diagenesis and Clay Mineral Formation at Gale Crater, Mars Authors: Bridges, JC; Schwenzer, S. P.; Leveille, R.; Westall, F.; Wiens, R. C.; Mangold, N.; Bristow, T.; Edwards, P.; Berger, G. Abstract: The Mars Science Laboratory rover Curiosity found host rocks of basaltic composition and alteration assemblages containing clay minerals at Yellowknife Bay, Gale Crater. On the basis of the observed host rock and alteration minerals, we present results of equilibrium thermochemical modeling of the Sheepbed mudstones of Yellowknife Bay in order to constrain the formation conditions of its secondary mineral assemblage. Building on conclusions from sedimentary observations by the Mars Science Laboratory team, we assume diagenetic, in situ alteration. The modeling shows that the mineral assemblage formed by the reaction of a CO2-poor and oxidizing, dilute aqueous solution (Gale Portage Water) in an open system with the Fe-rich basaltic-composition sedimentary rocks at 10–50°C and water/rock ratio (mass of rock reacted with the starting fluid) of 100–1000, pH of ~7.5–12. Model alteration assemblages predominantly contain phyllosilicates (Fe-smectite, chlorite), the bulk composition of a mixture of which is close to that of saponite inferred from Chemistry and Mineralogy data and to that of saponite observed in the nakhlite Martian meteorites and terrestrial analogues. To match the observed clay mineral chemistry, inhomogeneous dissolution dominated by the amorphous phase and olivine is required. We therefore deduce a dissolving composition of approximately 70% amorphous material, with 20% olivine, and 10% whole rock component. 2015-02-20T09:59:48Z GRB 130925A: an ultralong gamma ray burst with a dust-echo afterglow, and implications for the origin of the ultralong GRBs Evans, P. A. Willingale, R. Osborne, J. P. O'Brien, P. T. Tanvir, N. R. Frederiks, D. D. Pal'shin, V. D. Svinkin, D. S. Lien, A. Cummings, J. Xiong, S. Zhang, B-B. Goetz, D. Savchenko, V. Negoro, H. Nakahira, S. Suzuki, K. Wiersema, K. Starling, R. L. C. Castro-Tirado, A. J. Beardmore, A. P. Sanchez-Ramirez, R. Gorosabel, J. Jeong, S. Kennea, J. A. Burrows, D. N. Gehrels, N. http://hdl.handle.net/2381/31723 2015-02-20T02:01:55Z 2015-02-19T16:23:30Z Title: GRB 130925A: an ultralong gamma ray burst with a dust-echo afterglow, and implications for the origin of the ultralong GRBs Authors: Evans, P. A.; Willingale, R.; Osborne, J. P.; O'Brien, P. T.; Tanvir, N. R.; Frederiks, D. D.; Pal'shin, V. D.; Svinkin, D. S.; Lien, A.; Cummings, J.; Xiong, S.; Zhang, B-B.; Goetz, D.; Savchenko, V.; Negoro, H.; Nakahira, S.; Suzuki, K.; Wiersema, K.; Starling, R. L. C.; Castro-Tirado, A. J.; Beardmore, A. P.; Sanchez-Ramirez, R.; Gorosabel, J.; Jeong, S.; Kennea, J. A.; Burrows, D. N.; Gehrels, N. Abstract: GRB 130925A was an unusual gamma ray burst (GRB), consisting of three distinct episodes of high-energy emission spanning ∼20 ks, making it a member of the proposed category of 'ultralong' bursts. It was also unusual in that its late-time X-ray emission observed by Swift was very soft, and showed a strong hard-to-soft spectral evolution with time. This evolution, rarely seen in GRB afterglows, can be well modelled as the dust-scattered echo of the prompt emission, with stringent limits on the contribution from the normal afterglow (i.e. external shock) emission. We consider and reject the possibility that GRB 130925A was some form of tidal disruption event, and instead show that if the circumburst density around GRB 130925A is low, the long duration of the burst and faint external shock emission are naturally explained. Indeed, we suggest that the ultralong GRBs as a class can be explained as those with low circumburst densities, such that the deceleration time (at which point the material ejected from the nascent black hole is decelerated by the circumburst medium) is ∼20 ks, as opposed to a few hundred seconds for the normal long GRBs. The increased deceleration radius means that more of the ejected shells can interact before reaching the external shock, naturally explaining both the increased duration of GRB 130925A, the duration of its prompt pulses, and the fainter-than-normal afterglow. 2015-02-19T16:23:30Z Remote Sensing Education for Life Long Learning across the East Midlands Region Archibald, Alexandra Balzter, Heiko Monks, Paul S. Remedios, John J. Roth, Roman Smith, Teresa http://hdl.handle.net/2381/31680 2015-02-17T10:35:08Z 2015-02-17T10:34:04Z Title: Remote Sensing Education for Life Long Learning across the East Midlands Region Authors: Archibald, Alexandra; Balzter, Heiko; Monks, Paul S.; Remedios, John J.; Roth, Roman; Smith, Teresa Abstract: Over the last decade, remote sensing technologies have provided useful tools for a diverse range of sectors. G-STEP (GMES—space technology exchange partnership) is the University of Leicester's flagship project for innovation, training and education in GMES (global monitoring for environment and security) and GIS (geographical information systems) based technologies. G-STEP (part funded by the ERDF) is the first GMES accelerator initiative in the UK and is breaking new ground in the application of GMES and GIS. The core G-STEP team initiates and develops Knowledge Exchange Practices between the University and Life Long Learning partners in the East Midlands Region, through training packages and collaborative research projects. The programme integrates innovative research, to direct downstream applied training, supported by analytical processing of attendee assessment data. Collated information derived from these sources presents a unique opportunity to incorporate a statistically viable feedback cycle, making G-STEP the interface between pure and applied research, thus initiating downstream dissemination to groups and small business. In this paper, we outline the GMES and GIS training packages, and the route to market to increase uptake of underused data streams via university and regional entrepreneurs (start-ups) and established small business with a core interest in utilisation and dissemination of novel technologies in sustainable lifelong learning. 2015-02-17T10:34:04Z The tidal downsizing hypothesis for planet formation and the composition of Solar system comets Nayakshin, S. Cha, S-H. Bridges, JC http://hdl.handle.net/2381/31610 2015-02-06T02:01:52Z 2015-02-05T12:31:11Z Title: The tidal downsizing hypothesis for planet formation and the composition of Solar system comets Authors: Nayakshin, S.; Cha, S-H.; Bridges, JC Abstract: Comets are believed to be born in the outer Solar system where the temperature is assumed to have never exceeded T ∼ 100 K. Surprisingly, observations and samples of cometary dust particles returned to Earth showed that they are in fact made of a mix of ices, as expected, but also of materials forged at high temperatures (T ∼ 1500 K). We propose a radically new view regarding the origin of the high-temperature processed materials in comets, based on the recent 'tidal downsizing' hypothesis for planet formation. In the latter, the outer protoplanetary disc is gravitationally unstable and forms massive giant planet embryos (GEs). These hot (T ∼ 100–2000 K) and dense regions, immersed in the background cold and low-density disc, are eventually disrupted. We propose that both planets and the high-temperature materials in comets are synthesized inside the GEs. Disruption of GEs separates planets and small solids as the latter are 'frozen-in' into gas and are peeled off together with it. These small solids are then mixed with the ambient cold disc containing ices before being incorporated into comets. Several predictions of this picture may be testable with future observations of the exoplanets. 2015-02-05T12:31:11Z Structure and magnetic properties of Fe nanoparticles embedded in a Cr matrix Qureshi, M. T. Baker, S. H. Binns, C. Roy, Mervyn Laureti, S. Fiorani, D. Peddis, D. http://hdl.handle.net/2381/31587 2015-02-05T02:01:55Z 2015-02-04T15:23:17Z Title: Structure and magnetic properties of Fe nanoparticles embedded in a Cr matrix Authors: Qureshi, M. T.; Baker, S. H.; Binns, C.; Roy, Mervyn; Laureti, S.; Fiorani, D.; Peddis, D. Abstract: The structure of 2 nm diameter (340 atoms) Fe nanoparticles embedded in a Cr matrix was determined using X-ray Absorption Fine Structure (EXAFS) and the magnetic properties studied by Superconducting Quantum Interference Device (SQUID) magnetometry. The thin films were produced by the co-deposition of pre-formed gas-phase Fe clusters synthesised by a gas aggregation source with an atomic vapour of Cr produced by an MBE source. The behaviour was studied as a function of Fe nanoparticle volume fraction in the range 5-20% and was compared to previous results on ferromagnetic nanoparticles in antiferromagnetic matrices. EXAFS showed that the atomic structure in the Cr-embedded Fe nanoparticles is the same as the bulk bcc structure. Whereas alloying between the nanoparticles and matrix material has previously been shown to be very pronounced for Co nanoparticles in antiferromagnetic Mn, it was found that any alloying between Fe nanoparticles and Cr matrix material is limited. For dilute samples of Fe nanoparticles in Cr the measured saturation magnetisation (M) was 1μ/Fe atom, which is significantly less than the bulk M value of 2.22μ/Fe atom indicating that the surface of Fe nanoparticles is either antiferromagnetic or non-magnetic. An increase in the volume fraction produces an increase in the value of M and at a volume fraction of 20%, M exceeds the value of bulk Fe showing that some Cr spins provide a ferromagnetic contribution. After field cooling below 30 K, all films show Exchange Bias (EB) and an increase of coercivity, which are both much larger for the most concentrated sample. The Cr spins at the surface of the Fe particles play a key role in determining the overall magnetic behaviour. 2015-02-04T15:23:17Z The suppression of fluorescence peaks in energy-dispersive X-ray diffraction Hansford, Graeme M. Turner, S. M. R. Staab, D. Vernon, D. http://hdl.handle.net/2381/31580 2015-02-05T02:01:51Z 2015-02-04T12:01:48Z Title: The suppression of fluorescence peaks in energy-dispersive X-ray diffraction Authors: Hansford, Graeme M.; Turner, S. M. R.; Staab, D.; Vernon, D. Abstract: A novel method to separate diffraction and fluorescence peaks in energydispersive X-ray diffraction (EDXRD) is described. By tuning the excitation energy of an X-ray tube source to just below an elemental absorption edge, the corresponding fluorescence peaks of that element are completely suppressed in the resulting spectrum. Since Bremsstrahlung photons are present in the source spectrum up to the excitation energy, any diffraction peaks that lie at similar energies to the suppressed fluorescence peaks are uncovered. This technique is an alternative to the more usual method in EDXRD of altering the scattering angle in order to shift the energies of the diffraction peaks. However, in the back-reflection EDXRD technique [Hansford (2011). J. Appl. Cryst. 44, 514– 525] changing the scattering angle would lose the unique property of insensitivity to sample morphology and is therefore an unattractive option. The use of fluorescence suppression to reveal diffraction peaks is demonstrated experimentally by suppressing the Ca K fluorescence peaks in the backreflection EDXRD spectra of several limestones and dolomites. Three substantial benefits are derived: uncovering of diffraction peak(s) that are otherwise obscured by fluorescence; suppression of the Ca K escape peaks; and an increase in the signal-to-background ratio. The improvement in the quality of the EDXRD spectrum allows the identification of a secondary mineral in the samples, where present. The results for a pressed-powder pellet of the geological standard JDo-1 (dolomite) show the presence of crystallite preferred orientation in this prepared sample. Preferred orientation is absent in several unprepared limestone and dolomite rock specimens, illustrating an advantage of the observation of rocks in their natural state enabled by back-reflection EDXRD. 2015-02-04T12:01:48Z Mineralogy of four Itokawa particles collected from the first touchdown site Noguchi, T Bridges, JC Hicks, Leon J. Gurman, Steven J. Kimura, M Hashimoto, T Konno, M Bradley, JP Okazaki, R Uesugi, M Yada, T Karouji, Y Abe, M Okada, T Mitsunari, T Nakamura, T Kagi, H http://hdl.handle.net/2381/31555 2015-02-03T02:01:48Z 2015-02-02T16:21:37Z Title: Mineralogy of four Itokawa particles collected from the first touchdown site Authors: Noguchi, T; Bridges, JC; Hicks, Leon J.; Gurman, Steven J.; Kimura, M; Hashimoto, T; Konno, M; Bradley, JP; Okazaki, R; Uesugi, M; Yada, T; Karouji, Y; Abe, M; Okada, T; Mitsunari, T; Nakamura, T; Kagi, H Abstract: Four Itokawa particles collected from the first touchdown site were mineralogically investigated by optical microscopy, micro-Raman (μ-Raman) spectrometry, scanning electron microscopy (SEM), electron microprobe analysis (EPMA), X-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). Their mineralogy has an affinity to that of LL6 chondrites based on micro-Raman spectroscopy, EPMA, and XAS analyses. However, the space weathering rims on them are less developed than those observed on the Itokawa particles collected from the second touchdown site. Solar flare tracks are rarely observed in the four particles, whose number densities were lower than those observed in the Itokawa particles from the second touchdown site. 2015-02-02T16:21:37Z Mars Methane Detection and Variability at Gale Crater Webster, CR Mahaffy, P Atreya, SK Flesch, GJ Mischna, MA Meslin, P-Y Farley, KA Conrad, PG Christensen, LE Pavlov, AA Martin-Torres, J Zorzano, M-P McConnochie, TH Owen, T Eigenbrode, JE Glavin, DP Steele, A Malespin, A Archer, DP Sutter, B Coll, P Freissinet, P McKay, CP Moores, JE Schwenzer, SP Bridges, JC Navarro-Gonzalez, R Gellert, R Lemmon, MT http://hdl.handle.net/2381/31537 2015-02-03T02:01:49Z 2015-02-02T10:29:37Z Title: Mars Methane Detection and Variability at Gale Crater Authors: Webster, CR; Mahaffy, P; Atreya, SK; Flesch, GJ; Mischna, MA; Meslin, P-Y; Farley, KA; Conrad, PG; Christensen, LE; Pavlov, AA; Martin-Torres, J; Zorzano, M-P; McConnochie, TH; Owen, T; Eigenbrode, JE; Glavin, DP; Steele, A; Malespin, A; Archer, DP; Sutter, B; Coll, P; Freissinet, P; McKay, CP; Moores, JE; Schwenzer, SP; Bridges, JC; Navarro-Gonzalez, R; Gellert, R; Lemmon, MT Abstract: Reports of plumes or patches of methane in the Martian atmosphere that vary over monthly timescales have defied explanation to date. From in situ measurements made over a 20-month period by the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars (SAM) instrument suite on Curiosity at Gale Crater, we report detection of background levels of atmospheric methane of mean value 0.69 ±0.21 ppbv at the 95% confidence interval (CI). This abundance is lower than model estimates of ultraviolet (UV) degradation of accreted interplanetary dust particles (IDP's) or carbonaceous chondrite material. Additionally, in four sequential measurements spanning a 60-sol period, we observed elevated levels of methane of 7.19 ±1.99 (95% CI) ppbv implying that Mars is episodically producing methane from an additional unknown source. Description: Supplementary materials http://www.sciencemag.org/content/347/6220/415/suppl/DC1 2015-02-02T10:29:37Z Correction of the Photoelectron Heating Efficiency Within the Global Ionosphere-Thermosphere Model Using Retrospective Cost Model Refinement Burrell, Angeline G. Goel, A. Ridley, A. J. Bernstein, D. S. http://hdl.handle.net/2381/31515 2015-01-28T16:03:11Z 2015-01-28T16:02:16Z Title: Correction of the Photoelectron Heating Efficiency Within the Global Ionosphere-Thermosphere Model Using Retrospective Cost Model Refinement Authors: Burrell, Angeline G.; Goel, A.; Ridley, A. J.; Bernstein, D. S. Abstract: Many physics-based models are used to study and monitor the terrestrial upper atmosphere. Each of these models have internal parameterizations that introduce bias if they are not tuned for a specific set of run conditions. This study uses Retrospective Cost Model Refinement (RCMR) to remove internal model bias in the Global Ionosphere Thermosphere Model (GITM) through parameter estimation. RCMR is a low-cost method that uses the error between truth data and a biased estimate to improve the biased model. Neutral mass density measurements are used to estimate an appropriate photoelectron heating efficiency, which is shown to drive the modeled thermosphere closer to the real thermosphere. Observations from the Challenging Mini-Payload (CHAMP) satellite taken under active and quiet solar conditions show that RCMR successfully drives the GITM thermospheric mass density to the observed values, removing model bias and appropriately accounting for missing physical processes in the thermospheric heating through the photoelectron heating efficiency. Description: PII: S1364-6826(15)00006-1 2015-01-28T16:02:16Z SDSS J1138+3517: A quasar showing remarkably variable broad absorption lines Wildy, Conor Goad, Michael R. Allen, J. T. http://hdl.handle.net/2381/31468 2015-03-04T02:02:01Z 2015-01-21T16:53:02Z Title: SDSS J1138+3517: A quasar showing remarkably variable broad absorption lines Authors: Wildy, Conor; Goad, Michael R.; Allen, J. T. Abstract: We report on the highly variable Si iv and C iv broad absorption lines in SDSS J113831.4+351725.2 across four observational epochs. Using the Si iv doublet components, we find that the blue component is usually saturated and non-black, with the ratio of optical depths between the two components rarely being 2:1. This indicates that these absorbers do not fully cover the line-of-sight and thus a simple apparent optical depth model is insufficient when measuring the true opacity of the absorbers. Tests with inhomogeneous (power-law) and pure-partial coverage (step-function) models of the absorbing Si iv optical depth predict the most un-blended doublet's component profiles equally well. However, when testing with Gaussian-fitted doublet components to all Si iv absorbers and averaging the total absorption predicted in each doublet, the upper limit of the power law index is mostly unconstrained. This leads us to favour pure partial coverage as a more accurate measure of the true optical depth than the inhomogeneous power law model. The pure-partial coverage model indicates no significant change in covering fraction across the epochs, with changes in the incident ionizing flux on the absorbing gas instead being favoured as the variability mechanism. This is supported by (a) the coordinated behaviour of the absorption troughs, (b) the behaviour of the continuum at the blue end of the spectrum and (c) the consistency of photoionization simulations of ionic column density dependencies on ionization parameter with the observed variations. Evidence from the simulations together with the C iv absorption profile indicates that the absorber lies outside the broad line region, though the precise distance and kinetic luminosity are not well constrained. 2015-01-21T16:53:02Z Probing the structure and dynamics of molecular clusters using rotational wavepackets Galinis, Gediminas Cacho, C Chapman, R. T. Ellis, A. M. Lewerenz, M Mendoza Luna, Luis G. Minns, R. S. Mladenovic, M Rouzee, A Springate, E Turcu, I. C. E. Watkins, Mark J. von Haeften, Klaus http://hdl.handle.net/2381/31382 2015-01-09T02:01:40Z 2015-01-08T11:53:25Z Title: Probing the structure and dynamics of molecular clusters using rotational wavepackets Authors: Galinis, Gediminas; Cacho, C; Chapman, R. T.; Ellis, A. M.; Lewerenz, M; Mendoza Luna, Luis G.; Minns, R. S.; Mladenovic, M; Rouzee, A; Springate, E; Turcu, I. C. E.; Watkins, Mark J.; von Haeften, Klaus Abstract: Rotational wave packets of the weakly bound C2H2-He complex have been created using impulsive alignment. The coherent rotational dynamics were monitored for 600 ps enabling extraction of a frequency spectrum showing multiple rotational energy levels up to J = 4. spectrum has been combined with ab initio calculations to show that the complex has a highly delocalized structure and is bound only by ca. 7 cm−1. The experiments demonstrate how highly featured rotational spectra can be obtained from an extremely cold environment where only the lowest rotational energy states are initially populated. 2015-01-08T11:53:25Z Broadband modelling of short gamma-ray bursts with energy injection from magnetar spin-down and its implications for radio detectability Gompertz, Ben P. van der Horst, A. J. O'Brien, Paul T. Wynn, Graham A. Wiersema, Klaas http://hdl.handle.net/2381/31372 2015-01-08T02:01:40Z 2015-01-07T10:11:11Z Title: Broadband modelling of short gamma-ray bursts with energy injection from magnetar spin-down and its implications for radio detectability Authors: Gompertz, Ben P.; van der Horst, A. J.; O'Brien, Paul T.; Wynn, Graham A.; Wiersema, Klaas Abstract: The magnetar model has been proposed to explain the apparent energy injection in the X-ray light curves of short gamma-ray bursts (SGRBs), but its implications across the full broadband spectrum are not well explored. We investigate the broadband modelling of four SGRBs with evidence for energy injection in their X-ray light curves, applying a physically motivated model in which a newly-formed magnetar injects energy into a forward shock as it loses angular momentum along open field lines. By performing an order of magnitude search for the underlying physical parameters in the blast wave, we constrain the characteristic break frequencies of the synchrotron spectrum against their manifestations in the available multi-wavelength observations for each burst. The application of the magnetar energy injection profile restricts the successful matches to a limited family of models that are self-consistent within the magnetic dipole spin-down framework.We produce synthetic light curves that describe how the radio signatures of these SGRBs ought to have looked given the restrictions imposed by the available data, and discuss the detectability of these signatures with present day and near future radio telescopes. Our results show that both ALMA and the upgraded VLA are now sensitive enough to detect the radio signature within two weeks of trigger in most SGRBs, assuming our sample is representative of the population as a whole. We also find that the upcoming Square Kilometer Array will be sensitive to depths greater than those of our lower limit predictions. 2015-01-07T10:11:11Z Cassini nightside observations of the oscillatory motion of Saturn's northern auroral oval Bunce, Emma J. Grodent, D. C. Jinks, S. L. Andrews, D. J. Badman, S. V. Coates, A. J. Cowley, S. W. H. Dougherty, M. K. Kurth, W. S. Mitchell, D. G. Provan, G. http://hdl.handle.net/2381/29290 2014-11-25T02:01:39Z 2014-11-24T16:46:13Z Title: Cassini nightside observations of the oscillatory motion of Saturn's northern auroral oval Authors: Bunce, Emma J.; Grodent, D. C.; Jinks, S. L.; Andrews, D. J.; Badman, S. V.; Coates, A. J.; Cowley, S. W. H.; Dougherty, M. K.; Kurth, W. S.; Mitchell, D. G.; Provan, G. Abstract: In recent years we have benefitted greatly from the first in-orbit multi-wavelength images of Saturn's polar atmosphere from the Cassini spacecraft. Specifically, images obtained from the Cassini UltraViolet Imaging Spectrograph (UVIS) provide an excellent view of the planet's auroral emissions, which in turn give an account of the large-scale magnetosphere-ionosphere coupling and dynamics within the system. However, obtaining near-simultaneous views of the auroral regions with in situ measurements of magnetic field and plasma populations at high latitudes is more difficult to routinely achieve. Here we present an unusual case, during Revolution 99 in January 2009, where UVIS observes the entire northern UV auroral oval during a 2 h interval while Cassini traverses the magnetic flux tubes connecting to the auroral regions near 21 LT, sampling the related magnetic field, particle, and radio and plasma wave signatures. The motion of the auroral oval evident from the UVIS images requires a careful interpretation of the associated latitudinally "oscillating" magnetic field and auroral field-aligned current signatures, whereas previous interpretations have assumed a static current system. Concurrent observations of the auroral hiss (typically generated in regions of downward directed field-aligned current) support this revised interpretation of an oscillating current system. The nature of the motion of the auroral oval evident in the UVIS image sequence, and the simultaneous measured motion of the field-aligned currents (and related plasma boundary) in this interval, is shown to be related to the northern hemisphere magnetosphere oscillation phase. This is in agreement with previous observations of the auroral oval oscillatory motion. 2014-11-24T16:46:13Z Does ultraviolet astronomy have a future? Barstow, Martin A. http://hdl.handle.net/2381/29045 2014-08-20T01:01:31Z 2014-08-19T11:24:27Z Title: Does ultraviolet astronomy have a future? Authors: Barstow, Martin A. Abstract: Recent news of the cancellation of further servicing missions for HST and the recent failure of its prime UV spectrograph has brought into focus the limited future for UV astronomy, without rapid action. If this situation does not change, the routine access to the far-UV that we have enjoyed for more than 25 years, since the launch of IUE, will end by around 2008. Although the James Webb Space Telescope is planned to replace HST in the next decade, it is infrared-optimized and has no UV capability. Indeed, not one future UV/optical mission is currently approved by any space agency. This article reviews the status and likely future of the current UV missions, addresses the scientific importance of UV observations and presents a way forward that could fill the "UV-gap" in the decade beyond HST. 2014-08-19T11:24:27Z The pulsation modes of the pre-white dwarf PG 1159-035 Costa, J. E. S. Kepler, S. O. Winget, D. E. O'Brien, M. S. Kawaler, S. D. Costa, A. F. M. Giovannini, O. Kanaan, A. Mukadam, A. S. Mullally, F. Nitta, A. Provencal, J. L. Shipman, H. Wood, M. A. Ahrens, T. J. Grauer, A. Kilic, M. Bradley, P. A. Sekiguchi, K. Crowe, R. Jiang, X. J. Sullivan, D. Sullivan, T. Rosen, R. Clemens, J. C. Janulis, R. O'Donoghue, D. Ogloza, W. Baran, A. Silvotti, R. Marinoni, S. Vauclair, G. Dolez, N. Chevreton, M. Dreizler, S. Schuh, S. Deetjen, J. Nagel, T. Solheim, J-E. Gonzalez Perez, J. M. Ulla, A. Barstow, Martin A. Burleigh, Matthew R. Good, S. Metcalfe, T. S. Kim, S-L. Lee, H. Sergeev, A. Akan, M. C. Cakirli, O. Paparo, M. Viraghalmy, G. Ashoka, B. N. Handler, G. Huerkal, O. Johannessen, F. Kleinman, S. J. Kalytis, R. Krzesinski, J. Klumpe, E. Larrison, J. Lawrence, T. Meistas, E. Martinez, P. Nather, R. E. Fu, J-N. Pakstiene, E. Rosen, R. Romero-Colmenero, E. Riddle, R. Seetha, S. Silvestri, N. M. Vuckovic, M. Warner, B. Zolao, S. Althaus, L. G. Corsico, A. H. Montgomery, M. H. http://hdl.handle.net/2381/29044 2014-08-20T01:01:30Z 2014-08-19T11:03:36Z Title: The pulsation modes of the pre-white dwarf PG 1159-035 Authors: Costa, J. E. S.; Kepler, S. O.; Winget, D. E.; O'Brien, M. S.; Kawaler, S. D.; Costa, A. F. M.; Giovannini, O.; Kanaan, A.; Mukadam, A. S.; Mullally, F.; Nitta, A.; Provencal, J. L.; Shipman, H.; Wood, M. A.; Ahrens, T. J.; Grauer, A.; Kilic, M.; Bradley, P. A.; Sekiguchi, K.; Crowe, R.; Jiang, X. J.; Sullivan, D.; Sullivan, T.; Rosen, R.; Clemens, J. C.; Janulis, R.; O'Donoghue, D.; Ogloza, W.; Baran, A.; Silvotti, R.; Marinoni, S.; Vauclair, G.; Dolez, N.; Chevreton, M.; Dreizler, S.; Schuh, S.; Deetjen, J.; Nagel, T.; Solheim, J-E.; Gonzalez Perez, J. M.; Ulla, A.; Barstow, Martin A.; Burleigh, Matthew R.; Good, S.; Metcalfe, T. S.; Kim, S-L.; Lee, H.; Sergeev, A.; Akan, M. C.; Cakirli, O.; Paparo, M.; Viraghalmy, G.; Ashoka, B. N.; Handler, G.; Huerkal, O.; Johannessen, F.; Kleinman, S. J.; Kalytis, R.; Krzesinski, J.; Klumpe, E.; Larrison, J.; Lawrence, T.; Meistas, E.; Martinez, P.; Nather, R. E.; Fu, J-N.; Pakstiene, E.; Rosen, R.; Romero-Colmenero, E.; Riddle, R.; Seetha, S.; Silvestri, N. M.; Vuckovic, M.; Warner, B.; Zolao, S.; Althaus, L. G.; Corsico, A. H.; Montgomery, M. H. Abstract: Context. PG 1159-035, a pre-white dwarf with T[subscript eff] ≃ 140 000 K, is the prototype of both two classes: the PG 1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035 photometric data obtained with the Whole Earth Telescope (WET) showed a rich frequency spectrum allowing the identification of 122 pulsation modes. Analyzing the periods of pulsation, it is possible to measure the stellar mass, the rotational period and the inclination of the rotation axis, to estimate an upper limit for the magnetic field, and even to obtain information about the inner stratification of the star. Aims. We have three principal aims: to increase the number of detected and identified pulsation modes in PG 1159-035, study trapping of the star's pulsation modes, and to improve or constrain the determination of stellar parameters. Methods. We used all available WET photometric data from 1983, 1985, 1989, 1993 and 2002 to identify the pulsation periods. Results. We identified 76 additional pulsation modes, increasing to 198 the number of known pulsation modes in PG 1159-035, the largest number of modes detected in any star besides the Sun. From the period spacing we estimated a mass M/M☉ = 0.59 ± 0.02 for PG 1159-035, with the uncertainty dominated by the models, not the observation. Deviations in the regular period spacing suggest that some of the pulsation modes are trapped, even though the star is a pre-white dwarf and the gravitational settling is ongoing. The position of the transition zone that causes the mode trapping was calculated at r[subscript c]/R [subscript *] = 0.83 ± 0.05. From the multiplet splitting, we calculated the rotational period P[subscript rot] = 1.3920 ± 0.0008 days and an upper limit for the magnetic field, B < 2000 G. The total power of the pulsation modes at the stellar surface changed less than 30% for ℓ = 1 modes and less than 50% for ℓ = 2 modes. We find no evidence of linear combinations between the 198 pulsation mode frequencies. PG 1159-035 models have not significative convection zones, supporting the hypothesis that nonlinearity arises in the convection zones in cooler pulsating white dwarf stars. 2014-08-19T11:03:36Z Ferric saponite and serpentine in the nakhlite martian meteorites Hicks, Leon J. Bridges, JC Gurman, S. J. http://hdl.handle.net/2381/28993 2015-02-02T10:10:06Z 2014-07-18T15:35:07Z Title: Ferric saponite and serpentine in the nakhlite martian meteorites Authors: Hicks, Leon J.; Bridges, JC; Gurman, S. J. Abstract: Transmission electron microscopy and Fe-K X-ray absorption spectroscopy have been used to determine structure and ferric content of the secondary phase mineral assemblages in the nakhlite martian meteorites, NWA 998, Lafayette, Nakhla, GV, Y 000593, Y 000749, MIL 03346, NWA 817, and NWA 5790. The secondary phases are a rapidly cooled, metastable assemblage that has preserved Mg# and Ca fractionation related to distance from the fluid source, for most of the nakhlites, though one, NWA 5790, appears not to have experienced a fluid pathway. All nine nakhlite samples have also been analysed with scanning electron microscopy, electron probe micro analysis, Bright Field high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction. By measuring the energy position of the Fe-K XANES 1s → 3d pre-edge transition centroid we calculate the ferric content of the minerals within the nakhlite meteorites. The crystalline phyllosilicates and amorphous silicate of the hydrothermal deposits filling the olivine fractures are found to have variable Fe[superscript 3+]/ΣFe values ranging from 0.4 to 0.9. In Lafayette, the central silicate gel parts of the veins are more ferric than the phyllosilicates around it, showing that the fluid became increasingly oxidised. The mesostasis of Lafayette and NWA 817 also have phyllosilicate, which have a higher ferric content than the olivine fracture deposits, with Fe[superscript 3+]/ΣFe values of up to 1.0. Further study, via TEM analyses, reveal the Lafayette and NWA 817 olivine phyllosilicates to have 2:1 T–O–T lattice structure with a the d[subscript 001]-spacing of 0.96 nm, whereas the Lafayette mesostasis phyllosilicates have 1:1 T–O structure with d[subscript 001]-spacings of 0.7 nm. Based on our analyses, the phyllosilicate found within the Lafayette olivine fractures is trioctahedral ferric saponite (Ca[subscript 0.2]K[subscript 0.1])[subscript ∑0.3](Mg[subscript 2.6]Fe[superscript 2+, subscript 1.3]Fe[superscript 3+, subscript 1.7]Mn[subscript 0.1])[subscript ∑5.7][(Si[subscript 6.7] Al[superscript IV, subscript 0.9] Fe[superscript 3+, subscript 0.4])[subscript ∑8.0]O[subscript 20]](OH)[subscript 4]·nH[subscript 2]O, and that found in the mesostasis fractures is an Fe-serpentine (Ca[subscript 0.1]Mg[subscript 0.7]Fe[superscript 3+, subscript 1.0]Al[superscript VI, subscript 0.4])[subscript ∑2.2][Si[subscript 2]O[subscript 5]]OH[subscript 4], with a ferric gel of similar composition in Lafayette and found as fracture fills throughout the other nakhlites. 2014-07-18T15:35:07Z Disentangling Mie and attenuation effects in rain using a K[subscript a]-W dual-wavelength Doppler spectral ratio technique Tridon, Frédéric Battaglia, Alessandro Kollias, Pavlos http://hdl.handle.net/2381/28991 2014-07-18T14:39:59Z 2014-07-18T14:39:15Z Title: Disentangling Mie and attenuation effects in rain using a K[subscript a]-W dual-wavelength Doppler spectral ratio technique Authors: Tridon, Frédéric; Battaglia, Alessandro; Kollias, Pavlos Abstract: A novel technique that enables to disentangle Mie and attenuation effects in coincident, beam-matched K[subscript a]- and W-band radar observations is presented here. The ratio of the measured radar Doppler spectra at the two frequencies is estimated, and the Doppler velocity regime that corresponds to Rayleigh scatterers is determined. The range variation of the Rayleigh regime "plateau" is directly linked to the differential attenuation between the two wavelengths and does represent the attenuation component of the dual-wavelength ratio. The retrieval technique is applied to a light stratiform rain event and provides plausible results. The proposed Doppler spectral ratio methodology has potential for applications in precipitating snow, liquid and ice clouds and can be extended to other wavelength pairs. 2014-07-18T14:39:15Z Assessing the effect of spacecraft motion on single-spacecraft solar wind tracking techniques Conlon, Thomas M. Milan, Stephen E. Davies, J. A. http://hdl.handle.net/2381/28987 2014-07-18T10:34:50Z 2014-07-18T10:34:02Z Title: Assessing the effect of spacecraft motion on single-spacecraft solar wind tracking techniques Authors: Conlon, Thomas M.; Milan, Stephen E.; Davies, J. A. Abstract: Recent advances in wide-angle imaging by the Solar Mass Ejection Imager (SMEI) on board the Coriolis spacecraft and more recently by the Heliospheric Imagers (HI) aboard NASA's Solar TErrestrial RElations Observatory (STEREO), have enabled solar wind transients to be imaged and tracked from the Sun to 1 AU and beyond. In this paper we consider two of the techniques that have been used to determine the propagation characteristics of solar wind transients based on single-spacecraft observations, in particular propagation direction and radial speed. These techniques usually assume that the observing spacecraft remains stationary for the duration of observation of the solar wind transient. We determine the inaccuracy introduced by this assumption for the two STEREO spacecraft and find that it can be significant, and it can lead to an overestimation of the transient velocity as seen from STEREO-A and an underestimation as seen by STEREO-B. This has implications for the prediction or solar wind transients at 1 AU and hence is important for the study of space weather. 2014-07-18T10:34:02Z LDA DFT simulations of an isolated silicon donor on the (110) surface of GaAs Tilley, F. J. Roy, Mervyn Maksym, P. A. http://hdl.handle.net/2381/28942 2014-06-24T01:01:26Z 2014-06-23T13:36:37Z Title: LDA DFT simulations of an isolated silicon donor on the (110) surface of GaAs Authors: Tilley, F. J.; Roy, Mervyn; Maksym, P. A. Abstract: The convergence of the band gap state of a single silicon dopant on the (110) surface of GaAs was investigated. By simulating different sized super-cells we were able to show that a 3x4 super-cell provides a well converged calculation for modelling an isolated dopant, with the total energy being converged to 1 part in 1000. The local density of the silicon band gap state was then checked against a number of more intensive calculations and was found to be well converged, with an eigenvalue accurate to within 3 meV. 2014-06-23T13:36:37Z Generalised effective mass theory of sub-surface scanning tunnelling microscopy : application to weakly bound impurity states Roy, Mervyn Maksym, P. A. http://hdl.handle.net/2381/28941 2014-06-24T01:01:25Z 2014-06-23T13:27:14Z Title: Generalised effective mass theory of sub-surface scanning tunnelling microscopy : application to weakly bound impurity states Authors: Roy, Mervyn; Maksym, P. A. Abstract: We apply our generalised effective mass theory of sub-surface scanning tunnelling microscopy (STM) (Phys. Rev. B 19, 195304 (2010)) to simulate STM images of electronic states localised around sub-surface Si dopant atoms in GaAs. In the case of these shallow impurity-states, we demonstrate that electrostatic effects from image-charges and from the STM tip have a strong influence on the sub-surface state and hence the simulated image. 2014-06-23T13:27:14Z The distribution of metals in hot DA white dwarfs Dickinson, Nathan J. Barstow, Martin A. Hubeny, I. http://hdl.handle.net/2381/28776 2014-04-25T01:01:25Z 2014-04-24T10:53:56Z Title: The distribution of metals in hot DA white dwarfs Authors: Dickinson, Nathan J.; Barstow, Martin A.; Hubeny, I. Abstract: The importance to stellar evolution of understanding the metal abundances in hot white dwarfs is well known. Previous work has found the hot DA white dwarfs REJ 1032+532, REJ 1614-085 and GD 659 to have highly abundant, stratified photospheric nitrogen, due to the narrow absorption-line profiles of the far-ultraviolet (FUV) Nv doublet and the lack of extreme-ultraviolet (EUV) continuum absorption. A preliminary analysis of the extremely narrow, deep line profiles of the photospheric metal absorption features of PG 0948+534 suggested a similar photospheric metal configuration. However, other studies have found that REJ 1032+532, REJ 1614-085 and GD 659 can be well described by homogeneous models, with nitrogen abundances more in keeping with those of white dwarfs with higher effective temperatures. Here, a re-analysis of the nitrogen absorption features seen in REJ 1032+532, REJ 1614-085 and GD 659 is presented, with the aim of better understanding the structure of these stars, to test which models better represent the observed data and apply the results to the line profiles seen in PG 0948+534. A degeneracy is seen in the modelling of the nitrogen absorption-line profiles of REJ 1032+532, REJ 1614-085 and GD 659, with low-abundance, homogeneously distributed nitrogen models most likely being a better representation of the observed data. In PG 0948+534, no such degeneracy is seen, and the enigmatically deep line profiles could not be modelled satisfactorily. 2014-04-24T10:53:56Z Orbital and evolutionary constraints on the planet hosting binary GJ 86 from the Hubble Space Telescope Farihi, Jay Bond, H. E. Dufour, P. Haghighipour, N. Schaefer, G. H. Holberg, J. B. Barstow, Martin A. Burleigh, Matthew R. http://hdl.handle.net/2381/28775 2014-04-25T01:01:25Z 2014-04-24T10:38:37Z Title: Orbital and evolutionary constraints on the planet hosting binary GJ 86 from the Hubble Space Telescope Authors: Farihi, Jay; Bond, H. E.; Dufour, P.; Haghighipour, N.; Schaefer, G. H.; Holberg, J. B.; Barstow, Martin A.; Burleigh, Matthew R. Abstract: This paper presents new observations of the planet-hosting, visual binary GJ 86 (HR 637) using the Hubble Space Telescope. Ultraviolet and optical imaging with WFC3 confirms the stellar companion is a degenerate star and indicates the binary semimajor axis is larger than previous estimates, with a ≳ 28 au. Optical STIS spectroscopy of the secondary reveals a helium-rich white dwarf with C2 absorption bands and Teff = 8180 K, thus making the binary system rather similar to Procyon. Based on the 10.8 pc distance, the companion has 0.59 M⊙ and descended from a main-sequence A star of 1.9 M⊙ with an original orbital separation a ≳ 14 au. If the giant planet is coplanar with the binary, the mass of GJ 86Ab is between 4.4 and 4.7 MJup. The similarity of GJ 86 and Procyon prompted a re-analysis of the white dwarf in the latter system, with the tentative conclusion that Procyon hosts a planetesimal population. The periastron distance in Procyon is 20 per cent smaller than in α Cen AB, but the metal-enriched atmosphere of Procyon B indicates that the planet formation process minimally attained 25 km bodies, if not small planets as in α Cen. 2014-04-24T10:38:37Z A photospheric metal line profile analysis of hot DA white dwarfs with circumstellar material Dickinson, Nathan J. Barstow, Martin A. Welsh, B. Y. http://hdl.handle.net/2381/28774 2014-04-25T01:01:25Z 2014-04-24T10:27:39Z Title: A photospheric metal line profile analysis of hot DA white dwarfs with circumstellar material Authors: Dickinson, Nathan J.; Barstow, Martin A.; Welsh, B. Y. Abstract: Some hot DA white dwarfs have circumstellar high ion absorption features in their spectra, in addition to those originating in the photosphere. In many cases, the line profiles of these absorbing components are unresolved. Given the importance of the atmospheric composition of white dwarfs to studies of stellar evolution, extra-solar planetary systems and the interstellar medium, we examine the effect of including circumstellar line profiles in the abundance estimates of photospheric metals in six DA stars. The photospheric C and Si abundances are reduced in five cases where the circumstellar contamination is strong, though the relative weakness of the circumstellar Si IV absorption introduces minimal contamination, resulting in a small change in abundance. The inability of previous, approximate models to reproduce the photospheric line profiles here demonstrates the need for a technique that accounts for the physical line profiles of both the circumstellar and photospheric lines when modelling these blended absorption features. 2014-04-24T10:27:39Z The origin of hot white dwarf circumstellar features Dickinson, Nathan J. Barstow, Martin A. Burleigh, Matthew R. Farihi, Jay Welsh, B. Y. Redfield, S. Unglaub, K. http://hdl.handle.net/2381/28772 2014-04-24T10:15:34Z 2014-04-23T16:01:38Z Title: The origin of hot white dwarf circumstellar features Authors: Dickinson, Nathan J.; Barstow, Martin A.; Burleigh, Matthew R.; Farihi, Jay; Welsh, B. Y.; Redfield, S.; Unglaub, K. Abstract: We have analysed a sample of 23 hot DAs to better understand the source of the circumstellar features reported in previous work. Unambiguous detections of circumstellar material are again made at eight stars. The velocities of the circumstellar material at three of the white dwarfs are coincident with the radial velocities of interstellar medium (ISM) along the sight-line to the stars, suggesting that the objects may be ionizing the ISM in their locality. In three further cases, the circumstellar velocities are close to the ISM velocities, indicating that these objects are ionizing either the ISM or evaporated planetesimals/material in a circumstellar disc. The circumstellar velocity at WD 1614-084 lies far from the ISM velocities, indicating the ionization of either an undetected ISM component or circumstellar material. The material seen at WD0232+035 can be attributed to the photoionization of material lost from its M dwarf companion. The measured column densities of the circumstellar material lie within the ionized ISM column density ranges predicted to exist in hot DA Strömgren spheres.. 2014-04-23T16:01:38Z Sir Patrick Moore, 'The Sky at Night' and modern astronomy in the UK Abel, Paul Lintott, C Barstow, Martin A. http://hdl.handle.net/2381/28771 2014-04-24T01:01:17Z 2014-04-23T15:28:38Z Title: Sir Patrick Moore, 'The Sky at Night' and modern astronomy in the UK Authors: Abel, Paul; Lintott, C; Barstow, Martin A. Abstract: Paul Abel, Chris Lintott and Martin Barstow remember Patrick Moore and the part he played in shaping today's vibrant astronomical community. 2014-04-23T15:28:38Z Limits on the Dependence of the Fine-Structure Constant on Gravitational Potential from White-Dwarf Spectra Berengut, J. C. Flambaum, V. V. Ong, A. Webb, J. K. Barrow, J. D. Barstow, Martin A. Preval, Simon P. Holberg, J. B. http://hdl.handle.net/2381/28770 2014-04-24T01:01:17Z 2014-04-23T14:58:41Z Title: Limits on the Dependence of the Fine-Structure Constant on Gravitational Potential from White-Dwarf Spectra Authors: Berengut, J. C.; Flambaum, V. V.; Ong, A.; Webb, J. K.; Barrow, J. D.; Barstow, Martin A.; Preval, Simon P.; Holberg, J. B. Abstract: We propose a new probe of the dependence of the fine-structure constant α on a strong gravitational field using metal lines in the spectra of white-dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white-dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits of Δα/α=(4.2±1.6)×10−5 and (−6.1±5.8)×10−5 from FeV and NiV spectra, respectively, at a dimensionless gravitational potential relative to Earth of Δϕ≈5×10−5. With better determinations of the laboratory wavelengths of the lines employed these results could be improved by up to 2 orders of magnitude. 2014-04-23T14:58:41Z Where are all the Sirius-like binary systems? Holberg, J. B. Oswalt, T. D. Sion, E. M. Barstow, Martin A. Burleigh, Matthew R. http://hdl.handle.net/2381/28767 2014-04-24T01:01:23Z 2014-04-23T10:46:17Z Title: Where are all the Sirius-like binary systems? Authors: Holberg, J. B.; Oswalt, T. D.; Sion, E. M.; Barstow, Martin A.; Burleigh, Matthew R. Abstract: Approximately 70 per cent of the nearby white dwarfs appear to be single stars, with the remainder being members of binary or multiple star systems. The most numerous and most easily identifiable systems are those in which the main-sequence companion is an M star, since even if the systems are unresolved the white dwarf either dominates or is at least competitive with the luminosity of the companion at optical wavelengths. Harder to identify are systems where the non-degenerate component has a spectral type earlier than M0 and the white dwarf becomes the less luminous component. Taking Sirius as the prototype, these latter systems are referred to here as 'Sirius like'. There are currently 98 known Sirius-like systems. Studies of the local white dwarf population within 20 pc indicate that approximately 8 per cent of all white dwarfs are members of Sirius-like systems, yet beyond 20 pc the frequency of known Sirius-like systems declines to between 1 and 2 per cent, indicating that many more of these systems remain to be found. Estimates are provided for the local space density of Sirius-like systems and their relative frequency among both the local white dwarf population and the local population of A to K main-sequence stars. The great majority of currently unidentified Sirius-like systems will likely turn out to be closely separated and unresolved binaries. Ways to observationally detect and study these systems are discussed. 2014-04-23T10:46:17Z A comprehensive near- and far-ultraviolet spectroscopic study of the hot DA white dwarf G191-B2B Preval, Simon P. Barstow, Martin A. Holberg, J. B. Dickinson, Nathan J. http://hdl.handle.net/2381/28764 2014-04-24T01:01:23Z 2014-04-23T09:49:37Z Title: A comprehensive near- and far-ultraviolet spectroscopic study of the hot DA white dwarf G191-B2B Authors: Preval, Simon P.; Barstow, Martin A.; Holberg, J. B.; Dickinson, Nathan J. Abstract: We present a detailed spectroscopic analysis of the hot DA white dwarf G191-B2B, using the best signal-to-noise ratio, high-resolution near- and far-UV spectrum obtained to date. This is constructed from co-added Hubble Space Telescope (HST) Space Telescope Imaging Spectrometer (STIS) E140H, E230H and FUSE observations, covering the spectral ranges of 1150–3145 Å and 910–1185 Å, respectively. With the aid of recently published atomic data, we have been able to identify previously undetected absorption features down to equivalent widths of only a few mÅ. In total, 976 absorption features have been detected to 3σ confidence or greater, with 947 of these lines now possessing an identification, the majority of which are attributed to Fe and Ni transitions. In our survey, we have also potentially identified an additional source of circumstellar material originating from Si III. While we confirm the presence of Ge detected by Vennes et al., we do not detect any other species. Furthermore, we have calculated updated abundances for C, N, O, Si, P, S, Fe and Ni, while also calculating, for the first time, a non-local thermodynamic equilibrium abundance for Al, deriving Al III/H=1.60+0.07−0.08×10−7. Our analysis constitutes what is the most complete spectroscopic survey of any white dwarf. All observed absorption features in the FUSE spectrum have now been identified, and relatively few remain elusive in the STIS spectrum. 2014-04-23T09:49:37Z Longitudinal variations of plasmapause radius and the propagation of VLF noise within small (ΔL ∼ 0.5) extensions of the plasmasphere Smith, A. J. Carpenter, D. L. Lester, Mark http://hdl.handle.net/2381/28758 2014-04-15T01:01:20Z 2014-04-14T11:14:44Z Title: Longitudinal variations of plasmapause radius and the propagation of VLF noise within small (ΔL ∼ 0.5) extensions of the plasmasphere Authors: Smith, A. J.; Carpenter, D. L.; Lester, Mark Abstract: Simultaneous broadband whistler recordings made during the International Magnetospheric Study (IMS) at the two Antarctic stations Halley and Siple have been used to study longitudinal variations in the radius of the plasmapause observed during local afternoon. In both of the two periods studied thus far, whistler-derived equatorial electron density profiles imply an increase in plasmapause radius between the longitudes of Siple and Halley (Δϕ ∼ 30°) of ΔL ∼ 0.5. Intense VLF noise (∼2.5 kHz) was observed at Halley but not at Siple, and by echo analysis its propagation path was identified with that of a whistler component travelling close to the plasmapause within the region of larger radius. This leads to the conclusion that the noise was generated by a gyroresonance instability when energetic electrons (typically 10 keV), drifting eastwards in the plasmatrough, encountered enhanced plasma density in the small extension of the plasmasphere. 2014-04-14T11:14:44Z Large flow shears around auroral beads at substorm onset Hosokawa, K Milan, Steve E. Lester, Mark Kadokura, A Sato, N Bjornsson, G http://hdl.handle.net/2381/28757 2014-04-15T01:01:19Z 2014-04-14T10:59:07Z Title: Large flow shears around auroral beads at substorm onset Authors: Hosokawa, K; Milan, Steve E.; Lester, Mark; Kadokura, A; Sato, N; Bjornsson, G Abstract: We present a fine-scale electrodynamic structure behind the auroral beads observed immediately before substorm onset, as inferred from high spatial and temporal resolution measurements of substorm with an all-sky TV camera (ATV) and a coherent high frequency radar of Super Dual Auroral Radar Network in Iceland. On the night of 24 September 2006, the ATV observed eastward propagating auroral beads in the initial brightening arc of a substorm just prior to the poleward expansion. During the sequential passage of the beads across the radar beams, the radar detected large velocity flow shears whose magnitude was in excess of 0.27 s[superscript −1]. The observations suggest that flow shears were located very close to the center of the beads; thus, they corresponded to electric fields converging toward the beads, which is consistent with the existence of upward field-aligned currents (FACs) flowing out of the beads. The temporal and spatial resolutions of the current radar measurement were still insufficient for fully resolving the detailed electrodynamic structure behind the fast moving auroral beads. At least, however, we can suggest the existence of highly localized filamentary FAC structures behind the beads, which would be an important consequence of possible plasma instabilities operating in the M-I coupling region or near the equatorial plane of the magnetosphere. 2014-04-14T10:59:07Z


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Some of our lambs for 2014.
Denise Biggs shared this photo in the Women in Ag Facebook group.
Reader Anna Clark shared this photo with the Women in Ag Facebook group. It's the first baby yak of the year on her farm. She says, "Yaks are raised for meat, fiber, milk, packing, protection…
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Slashdot videos: Now with more Slashdot!
We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).
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toruonu (1696670) writes "How do you keep track of what's in your datacenter, where it is, what it's connected to and what is it doing right now? I mean I have built a datacenter from scratch over the years and I have machines from Sun, IBM, HP, Supermicro. I have machines that are simple workernodes and machines that are heavy grade storage consolidation machines. Then there are tens of switches, some for interconnect, some for management and don't get me started on the UPS-s etc. So how does one keep any kind of decent track of such a system as the current form of twiki pages with various tables just doesn't cut it anymore and I'm looking for a freeware solution that could actually show me a visual representation of the various nodes in the racks, their connections and dependencies. Just to give a simple example, if I'm going to disconnect UPS #3 right now and swap switch #5, which machines should I even consider taking offline?"


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Written on: 08/08/2013 by cardinal007 (1 review written)
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It is that magical time every week when a few of our favorite staff
loudmouths pundits get together to argue constructively talk about gaming news. Ross, Keri and Blake are back once again to pick away at every boring bit captivating morsel of news that was worth discussing. Some of the stories that were shouted about incessantly quietly discussed like mature adults were games coming to Google Plus, GameFly's upcoming unlimited play PC plan, and the validity of Diablo III's cash auction house
Ross decided that this week he didn't want to whip up a new Top 5, so he instead decided to read a passage from a gamer's guide that he one day wishes to write about how to win at life. Give it a listen. I may damn well change your life…
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Links to Topics Discussed:
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2. New PSN update is primarily PlayStation Plus focused
3. GameFly soon will offer PC gamers an "Unlimited" package
4. Cash auction houses to debut in Diablo III
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- Two hardcore and a casual gamer:Keri Honea, Ross Polly and Blake Grundman
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Officials search for poachers who killed deer, removed antlers near Killdeer
Wildlife officials are looking for the person or persons responsible for killing several deer and leaving them to rot northwest of Killdeer, according to the North Dakota Game and Fish Department.
Bucks, both mule deer and whitetail, were shot Friday night and the antlers were removed with the meat left. Hunters in the area discovered the deer Saturday morning.
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