Near-infrared counterparts to the Galactic Bulge Survey X-ray source population
Greiss, S × Steeghs, D Jonker, P. G Torres, M. A. P Maccarone, T. J Hynes, R. I Britt, C. T Nelemans, Gijs Gaensicke, B. T #
Priestley and Weale
Monthly Notices of the Royal Astronomical Society vol:438 issue:4 pages:2839-2852
We report on the near-infrared matches, drawn from three surveys, to the 1640 unique X-ray sources detected by Chandra in the Galactic Bulge Survey (GBS). This survey targets faint X-ray sources in the bulge, with a particular focus on accreting compact objects. We present all viable counterpart candidates and associate a false alarm probability (FAP) to each near-infrared match in order to identify the most likely counterparts. The FAP takes into account a statistical study involving a chance alignment test, as well as considering the positional accuracy of the individual X-ray sources. We find that although the star density in the bulge is very high, ˜90 per cent of our sources have an FAP <10 per cent, indicating that for most X-ray sources, viable near-infrared counterparts candidates can be identified. In addition to the FAP, we provide positional and photometric information for candidate counterparts to ˜95 per cent of the GBS X-ray sources. This information in combination with optical photometry, spectroscopy and variability constraints will be crucial to characterize and classify secure counterparts.