First period investigation and light-curve study of the eclipsing contact binary V776 Cas

CCD photometry of the eclipsing binary system V776 Cas was carried out through Johnson-Cousins UBVR filters in Dr. Mojtahedi observatory of Birjand University during August and September 2014. The physical and geometrical parameters of the system were obtained by analyzing the light curves. Radial velocity data were used to determine the absolute parameters. Five new times of minimum light were found. The O-C diagram was plotted relying on these times and the previously reported times of minimum. New ephemeris of the system, the rate of orbital period variations and the mass transfer rate of the system were derived from the O-C diagram analysis. A periodic variation of about 8 years was found from the O-C diagram analysis. At first light-time effect was considered. Although the results confirmed the probability of the presence of third body, Applegate mechanism was checked as the reason for this periodic variation and this mechanism is also in agreement with the observations.