Astron. Astrophys. Suppl. Ser. 142, 31-34

A period study of the W UMa type contact binary V 781 Tauri

Qingyao Liu and Yulan Yang

Send offprint request: Qingyao Liu

Yunnan Observatory, Chinese Academy of Sciences, Kunming, Yunnan, China
United Laboratory of Optical Astronomy, Chinese Academy of Sciences, China
National Astronomical Observatories, Chinese Academy of Sciences, China
e-mail: bily@public.km.yn.cn

Received May 25; accepted November 2, 1999

Abstract:

New times of minimum light determined from the observations of the W UMa type contact binary V 781 Tau are presented. According to these times of minima and those collected from the references, the change in the orbital period of the system is analyzed. The result reveals that the orbital period of V 781 Tau decreased continually from 1949 to 1998 and the change rate in the period is $\delta{p}/p=-5.0~{10^{-11}}$. The decrease in the period of the binary is explained by a model of the contracting secondary component of the system. The shrinking velocity of 6.77 10^-5 cm s^-1 as responsible for the change in the orbital period of the system is obtained, which is in agreement with the results shown in the study of the thermal relaxation oscillation of contact binaries by Wang (1994).

Key words: stars: binaries: close -- stars: binaries: general -- stars: kinematics