A Photometric Study of the Eclipsing Dwarf Nova GY Cnc in Quiescence and During an Outburst

The results of photometric observations of the dwarf nova GY Cnc in the Rc filter acquired in 2013-2015 (similar to 3900 orbital cycles, 19 nights in total) are presented, including observations during its outburst in April 2014. The binary's orbital elements have been refined. The orbital period has changed only insignificantly during the similar to 30 000P (orb) since the earlier observations; no systematic O-C variations were detected, only fluctuations within 0.004(d) on time scales of 1500-2000P (orb). A "combined" model is used to solve for the parameters of GY Cnc during two states of the system. The flux from the white dwarf is negligible due to the star's small size. The temperature of the donor star, T (2) similar to 3667 K (Sp M0.2 V), varies between 3440 and 3900 K (Sp K8.8-M1.7 V). The semi-major axis of the disk is a similar to 0.22a(0), on average. In quiescence, a varies within similar to 40%. The disk has a considerable eccentricity (e similar to 0.2-0.3) for a < 0.2a(0). The disk shape becomes more circular (e < 0.1) with increasing a. The outburst of GY Cnc was associated with increased luminosity of the disk due to the parameter alpha (g) (related to the viscosity of the disk material) decreasing to 0.1-0.2 and the temperature in the inner parts of the disk increasing twofold, to T (in) similar to 95 000 K. These changes were apparently due to the infall of matter onto the surface of the white dwarf as the outburst developed. All parameters of the accretion disk in quiescence display considerable variations about their mean values.