ИСТИНА

GY Cnc is one of a few deeply eclipsing long-period dwarf nova. CCD observations of GY Cnc were carried out during three observational seasons, i.e. autumn 2013, spring 2014 and 2015, with 50 and 60 cm telescopes in Crimea. The search of periodicities was carried out with Lafler-Kinman method which supplied us with value Porb = 0d.1754420. This period is in good agreement with the previous estimations and places GY Cnc longward of the 2-3 h gap on the distribution of CVs periods. During photometric monitoring of this dwarf nova, we discovered that it was undergoing an outburst in April 2014. The light curve in Rc band obtained on April 10, 2014 reveals that it becomes brighter on 3.5 mag. The system declined to quiescence a few days later, on April 20. During the outburst, the light curve showed a reflection effect and a possible shallow secondary eclipse around phase 0.5. Brightness changes were found during quiescence that can be interpreted as a variable mass transfer and mass accretion. In frames of combined model Khruzina (2011) worked out for eclipsing CV-s, observational light curves of GY Cnc were fitted with theoretical ones, parameters of the system components and their contribution to the total brightness were estimated.