A Period Change Study of the Contact Binary System YY Eri

The W UMa type of the eclipsing binary system YY Eri was observed by using a 0.7-meter telescope with a CCD photometric system in B, V, and R filters at the Regional Observatory for the Public, Chachoengsao, Thailand, on 5 December 2018, from 12:30 PM to 10:00 PM, UT. The obtained data were calculated using the photometry method to construct the light curve of each wavelength band and determine the minimum time. HJD 2458458.306 and HJD 2458458.144 are the minimum time of the primary and secondary eclipse, respectively. The data were used to plot the O-C curve. The upward parabolic curve means the period increases at the rate of 4.57× 10-3 seconds/year. The sinusoidal curve suggests that YY Eri might have a third body which is located at a distance of about 3.45 AU from the center of mass with an orbital period of 68.6 years.