Sample of optically unidentified x-ray binaries in the galactic bulge: Constraints on the physical nature from infrared photometric surveys

Abstract

We report on archival near-infrared and mid-infrared observations of seven persistent Xray sources situated in the Galactic bulge, using data from the UK Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS), the Spitzer Galactic Legacy Infrared Mid- Plane Survey Extraordinaire (GLIMPSE) and the Wide-field Infrared Survey Explorer (WISE) all-sky survey. We were able to successfully identify or provide upper flux limits for the systems SAX J1747.0-2853, IGR J17464-2811, AX J1754.2-2754, IGR J17597-2201, IGR J18134-1636, IGR J18256-1035 and Ser X-1 and constrain the nature of these systems. In the case of IGR J17597-2201, we present arguments that the source accretes matter from the stellar wind rather than via Roche-lobe overflow of the secondary. We suggest that, at its X-ray luminosity of 1034-35 erg s-1, we are probing the poorly known class of wind-fed low-mass X-ray binaries (LMXBs).