Bulut, A.Bulut, I.Cicek, C.Erdem, A.2025-01-272025-01-272016978-0-7354-1369-60094-243Xhttps://doi.org/10.1063/1.4944135https://hdl.handle.net/20.500.12428/242319th International Physics Conference of the Balkan-Physical-Union (BPU) -- AUG 24-27, 2015 -- Istanbul Univ, Beyazit Campus, Istanbul, TURKEYIn 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.eninfo:eu-repo/semantics/closedAccessbinarieseclipsinglight-time effectstars: individual: V700 Cyg and PY LyrConference Object172210.1063/1.4944135N/AWOS:0003759233000162-s2.0-84984533440Q4