CXOGBS J174444.7-260330: a new long orbital period cataclysmic variable in a low state
Abstract
We present phase-resolved spectroscopy and photometry of a source discovered with the Chandra Galactic Bulge Survey (GBS), CXOGBS J174444.7-260330 (aka CX93 and CX153 in the previously published GBS list). We find two possible values for the orbital period P, differing from each other by ∼13 s. The most likely solution is P = 5.690 14(6) h. The optical lightcurves show ellipsoidal modulations, whose modelling provides an inclination of 32±1° for the most likely P. The spectra are dominated by a K5 V companion star (the disc veiling is ≲5 per cent). Broad and structured emission from the Balmer lines is also detected, as well as fainter emission from He i. From the absorption lines we measure K2 = 117 ± 8 km s- 1 and v sin i = 69 ± 7 km s- 1. By solving the system mass function we find M1 = 0.8 ± 0.2 M⊙ for the favoured P and i, consistent with a white dwarf accretor, and M2 = 0.6 ± 0.2 M⊙. We estimate a distance in the range 400-700 pc. Although in a low accretion state, both spectroscopy and photometry provide evidence of variability on a time-scale of months or faster. Besides finding a new, long orbital period cataclysmic variable (CV) in a low accretion state, this work shows that the design of the GBS works efficiently to find accreting X-ray binaries in quiescence, highlighting that the spectra of CVs in a low accretion state can at times appear suggestive of a quiescent neutron star or a black hole system.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2013
- DOI:
- 10.1093/mnras/sts292
- arXiv:
- arXiv:1211.1194
- Bibcode:
- 2013MNRAS.428.3543R
- Keywords:
-
- accretion: accretion discs;
- stars: dwarf novae;
- stars: individual: CXOGBS J174444.7-260330;
- novae;
- cataclysmic variables;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 9 pages, 5 figures. Accepted for publication in MNRAS