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 show a cyclic variation with a 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, then its mass can be derived as M3 sin i' ≈ 91.08 MJup, and it should be a low-mass star. In addition, several physical parameters were measured. The color of the secondary star was determined to be V − R = 0.77(±0.03) which corresponds to a spectral type of K2–3. The secondary star's mass was estimated as M2 = 0.73(±0.02) M⊙ by combing the derived V − R value around phase 0 with the assumption that it obeys the mass-luminosity relation for main sequence stars. This mass is consistent with the mass—period relation for CV donor stars. For the white dwarf, the eclipse durations and contacts of the white dwarf yield an upper limit on the white dwarf's radius corresponding to a lower limit on mass of M1 ≈ 0.501 M⊙. The overestimated radius and previously published spectral data indicate that the boundary layer may have a very high temperature.