An orbital period investigation of the WUMa-type binary Y Sextantis

Four charge-coupled device (CCD) photometric times of light minimum of the overcontact binary Y Sex obtained from 2004 to 2007 are presented. It has been discovered that the light curve of Y Sex is variational. Combining the present times of light minimum with values collected from the literature, we investigated the orbital period changes of the system. It has been found that there may exist two cyclic period oscillations in the O-C diagram of Y Sex. One oscillates at a period of 51.22 yr with an amplitude of 0.0218 d, and the other changes at a period of 32.10 yr with an amplitude of 0.0100d. The period oscillations can be explained either by the light-time effect via the presence of an unseen third body and an unseen fourth body or by magnetic-activity cycles of the components.