Physical parameters and orbital period variation of a newly discovered cataclysmic variable GSC 4560-02157

Abstract

GSC 4560-02157 is a new eclipsing cataclysmic variable with an orbital period of $0.265359$ days. By using the published $V-$ and $R-$band data together with our observations, we discovered that the $O-C$ curve of GSC 4560-02157 may shows a cyclic variation with the period of $3.51$ years and an amplitude of $1.40$ min. If this variation is caused by a light travel-time effect via the existence of a third body, its mass can be derived as $M_{3}sin{i}^{\prime }\approx 91.08M_{Jup}$, it should be a low-mass star. In addition, several physical parameters were measured. The colour of the secondary star was determined as $V-R=0.77(\pm 0.03)$ which corresponds to a spectral type of K2-3. The secondary star's mass was estimated as $M_2=0.73(\pm 0.02)M_{\odot }$ by combing the derived $V-R$ value around phase 0 with the assumption that it obeys the mass-luminosity relation of the main sequence stars. This mass is consistent with the mass$-$period relation of CV donor stars. For the white dwarf, the eclipse durations and contacts of the white dwarf yield an upper limit of the white dwarf's radius corresponding to a lower limit mass of $M_1\approx 0.501M_{\odot }$. The overestimated radius and previously published spectral data indicate that the boundary layer may has a very high temperature.

10 pages, 7 figures