Near-infrared counterparts of three transient very faint neutron star X-ray binaries

Abstract

We present near-infrared (NIR) imaging observations of three transient neutron star X-ray binaries, SAX J1753.5-2349, SAX J1806.5-2215 and AX J1754.2-2754. All three sources are members of the class of `very faint' X-ray transients which exhibit X-ray luminosities $L_X\lesssim 10^{36}$ erg s${}^{-1}$. The nature of this class of sources is still poorly understood. We detect NIR counterparts for all three systems and perform multi-band photometry for both SAX J1753.5-2349 and SAX J1806.5-2215, including narrow-band Br${}_{\gamma }$ photometry for SAX J1806.5-2215. We find that SAX J1753.5-2349 is significantly redder than the field population, indicating that there may be absorption intrinsic to the system, or perhaps a jet is contributing to the infrared emission. SAX J1806.5-2215 appears to exhibit absorption in Br${}_{\gamma }$, providing evidence for hydrogen in the system. Our observations of AX J1754.2--2754 represent the first detection of a NIR counterpart for this system. We find that none of the measured magnitudes are consistent with the expected quiescent magnitudes of these systems. Assuming that the infrared radiation is dominated by either the disc or the companion star, the observed magnitudes argue against an ultracompact nature for all three systems.

10 pages, 10 figures, accepted for publication in MNRAS

References in corpus (13)

• The UKIDSS Galactic Plane Survey
• Six new candidate ultracompact X-ray binaries
• A Black Hole Nova Obscured by an Inner Disk Torus
• Sedimentation and Type I X-ray Bursts at Low Accretion Rates
• The behavior of subluminous X-ray transients near the Galactic center as observed using the X-ray telescope aboard Swift
• The nature of very faint X-ray binaries; hints from light curves
• Novel modelling of ultra-compact X-ray binary evolution - stable mass transfer from white dwarfs to neutron stars
• Near-Infrared Counterparts to Chandra X-ray Sources toward the Galactic Center. I. Statistics and a Catalog of Candidates
• Registration of the First Thermonuclear X-ray Burst from AX J1754.2-2754
• Optical and near-infrared spectroscopy of the black hole GX 339-4 II. The spectrocopic content in the low/hard and high/soft states
• ALMA observations of 4U 1728-34 and 4U 1820-30: first detection of neutron star X-ray binaries at 300 GHz
• Outbursts in ultracompact X-ray binaries
• Sample of optically unidentified X-ray binaries in the Galactic bulge. Constraints on the physical nature from infrared photometric surveys