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

## TL;DR

This study presents optical and infrared observations of CXOGBS J174623.5-310550, constraining its nature as a potential low-mass X-ray binary or cataclysmic variable with an M-type star, but without clear evidence of the donor star.

## Contribution

The paper provides detailed spectroscopic and photometric analysis to constrain the binary's orbital period and nature, suggesting it is either a short-period eclipsing CV or a foreground LMXB.

## Key findings

- No radial velocity variations detected, indicating the M-type star is not the donor.
- Estimated distance of 1.3-1.8 kpc for the system.
- Possible orbital period less than 2.2 hours, consistent with a CV or foreground LMXB.

## Abstract

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 Halpha emission line. The analysis of X-shooter spectroscopy covering 3 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% 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 hr orbital period eclipsing cataclysmic variable or a low-mass X-ray binary lying in the foreground of the Galactic Bulge.