We present modelling of the long-term optical light and radial velocity curves of the binary stellar system CXOGBS J175553.2-281633, first detected in X-rays in the Chandra Galactic Bulge Survey. We analysed 7 yr of optical I-band photometry from Optical Gravitational Lensing Experiment and found long-term variations from year to year. These long-term variations can most likely be explained with by either variations in the luminosity of the accretion disc or a spotted secondary star. The phased light curve has a sinusoidal shape, which we interpret as being due to ellipsoidal modulations. We improve the orbital period to be P = 10.34488 +/- 0.00006 h with a time of inferior conjunction of the secondary star T-0 = HJD2455260.8204 +/- 0.0008. Moreover, we collected 37 spectra over 6 non-consecutive nights. The spectra show evidence for an evolved K7 secondary donor star, from which we obtain a semi-amplitude for the radial velocity curve of K-2 = 161 +/- 6 km s(-1). Using the light-curve synthesis code xrbinary, we derive the most likely orbital inclination for the binary of i = 63.0 +/- 0.7 deg, a primary mass of M-1 = 0.83 +/- 0.06 M-circle dot, consistent with a white dwarf accretor, and a secondary donor mass of M-2 = 0.65 +/- 0.07 M-circle dot, consistent with the spectral classification. Therefore, we identify the source as a long orbital period cataclysmic variable star.
Publication Source (Journal or Book title)
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Gomez, S., Torres, M. A., Jonker, P. G., Kostrzewa-Rutkowska, Z., van Grunsven, T. F., Udalski, A., Hynes, R. I., Heinke, C. O., Maccarone, T. J., Salinas, R., & Strader, J. (2021). Dynamical modelling of CXOGBS J175553.2-281633: a 10 h long orbital period cataclysmic variable. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 502 (1), 48-59. https://doi.org/10.1093/mnras/stab026