A Phenomenological Model for the Light Curve of Three Quiescent Low-inclination Dwarf Novae and One Pre-cataclysmic Variable

Abstract

Abstract We used the light curve code XRBinary to model the quiescent K2 light curves of three low-inclination cataclysmic variables (CVs): 1RXS J0632+2536 (J0632+2536), RZ Leo, TW Vir and the pre-CV WD 1144+011. Optimized light curve models were obtained using a nonlinear fitting code NMfit and visualized by Phoebe 2.0. The disk model of J0632+2536 shows that one hotspot at the edge of the disk is enough to describe its light curve, while the other two dwarf nova (DN): RZ Leo and TW Vir require two hotspots. A typical pre-CV model with a weak irradiation effect for WD 1144+011 can explain its single-hump modulation and the newly observed spectrum confirms its previous classification. The synthetic analyses for the DN clearly indicate that phase zero of the double-hump modulations occurs around the secondary minimum and the primary hump is mainly caused by the hotspot at the edge of the disk. The quiescent disk has a flat temperature distribution with a power index of ∼0.11. The disk model of RZ Leo implies a truncated disk, supporting its previously speculated classification as an intermediate polar (IP). Except for the IP model of RZ Leo, which lacks a component related to the inferred accretion curtain, the models of J0632+2536, TW Vir and WD 1144+011 are consistent with results from the Gaia mission. The derived masses and radii of the secondaries of the three DN are consistent with the semi-empirical relations for CV donor stars, while their effective temperatures are higher than the predictions. Irradiation of the donor stars is investigated to explain this discrepancy.