9th International Physics Conference of the Balkan-Physical-Union (BPU), İstanbul, Turkey, 24 - 27 August 2015, vol.1722
In this paper, orbital period variations of these two contact binaries (V700 Cyg and PY Lyr) were studied. O-C diagrams of these binaries were analyzed with the least-squares method by using all available times of minima. Apparent period changes of these two contact binaries were explained in terms of light-time effect due to a third body. Masses of third bodies were found to be 0.014 +/- 0.001 M-circle dot and 0.130 +/- 0.006 M-circle dot for V700 Cyg and PY Lyr, respectively.