Sample of optically unidentified X-ray binaries in the Galactic bulge. Constraints on the physical nature from infrared photometric surveys

TL;DR

This study uses infrared surveys to identify and analyze the nature of seven persistent X-ray sources in the Galactic bulge, revealing insights into their accretion mechanisms and classifying a subset as wind-fed low-mass X-ray binaries.

Contribution

It provides new infrared observations and constraints on the physical nature of previously unidentified X-ray binaries in the Galactic bulge, including evidence for wind-fed accretion.

Findings

Identified or constrained flux limits for 7 X-ray sources.

Suggested IGR J17597-2201 is a wind-fed low-mass X-ray binary.

Probed the properties of systems at luminosities of 10^{34-35} erg s^{-1}.

Abstract

We report on the archival near-infrared and mid-infrared observations of 7 persistent X-ray sources situated in the Galactic bulge using data from the UKIRT Infrared Deep Sky Survey (UKIDSS), 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, 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 $10^{34-35}$ erg s$^{-1}$, we are probing the poorly known class of wind-fed low-mass X-ray binaries (LMXBs).