Constraining the nature of the accreting binary in CXOGBS J174623.5-310550

Torres, M. A. P.; Repetto, S.; Wevers, T.; Heida, M.; Jonker, P. G.; Hynes, R. I.; Nelemans, G.; Kostrzewa-Rutkowska, Z.; Wyrzykowski, L.; Britt, C. T.; Heinke, C. O.; Casares, J.; Johnson, C. B.; Maccarone, T. J.; Steeghs, D. T. H.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society, Volume 487, Issue 2, p.2296-2306

Advertised on:
8
2019
Number of authors
15
IAC number of authors
2
Citations
6
Refereed citations
4
Description
We report optical and infrared observations of the X-ray source CXOGBS J174623.5-310550. This Galactic object was identified as a potential quiescent low-mass X-ray binary accreting from an M-type donor on the basis of optical spectroscopy and the broad H α emission line. The analysis of X-shooter spectroscopy covering three consecutive nights supports an M2/3-type spectral classification. Neither radial velocity variations nor rotational broadening is detected in the photospheric lines. No periodic variability is found in I- and r'-band light curves. We derive r' = 20.8, I = 19.2, and Ks ≈ 16.6 for the optical and infrared counterparts with the M-type star contributing {≈ }90{{ per cent}} to the I-band light. We estimate its distance to be 1.3-1.8 kpc. The lack of radial velocity variations implies that the M-type star is not the donor star in the X-ray binary. This could be an interloper or the outer body in a hierarchical triple. We constrain the accreting binary to be a ≲2.2 h orbital period eclipsing cataclysmic variable or a low-mass X-ray binary lying in the foreground of the Galactic bulge.
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