Title: Candidate Hα emission and absorption line sources in the Galactic Bulge Survey,
Abstract: We present a catalogue of candidate H{\alpha} emission and absorption line
sources and blue objects in the Galactic Bulge Survey (GBS) region. We use a
point source catalogue of the GBS fields (two strips of (l x b) = (6 x 1)
degrees centred at b = 1.5 above and below the Galactic centre), covering the
magnitude range 16 < r' < 22.5. We utilize (r'-i', r'-H{\alpha}) colour-colour
diagrams to select H{\alpha} emission and absorption line candidates, and also
identify blue objects (compared to field stars) using the r'-i' colour index.
We identify 1337 H{\alpha} emission line candidates and 336 H{\alpha}
absorption line candidates. These catalogues likely contain a plethora of
sources, ranging from active (binary) stars, early-type emission line objects,
cataclysmic variables (CVs) and low-mass X-ray binaries (LMXBs) to background
active galactic nuclei (AGN). The 389 blue objects we identify are likely
systems containing a compact object, such as CVs, planetary nebulae and LMXBs.
Hot subluminous dwarfs (sdO/B stars) are also expected to be found as blue
outliers. Crossmatching our outliers with the GBS X-ray catalogue yields
sixteen sources, including seven (magnetic) CVs and one qLMXB candidate among
the emission line candidates, and one background AGN for the absorption line
candidates. One of the blue outliers is a high state AM CVn system.
Spectroscopic observations combined with the multi-wavelength coverage of this
area, including X-ray, ultraviolet and (time-resolved) optical and infrared
observations, can be used to further constrain the nature of individual
sources.