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Issue A&A
Volume 390, Number 2, August I 2002
Page(s) 555 - 559
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020753



A&A 390, 555-559 (2002)
DOI: 10.1051/0004-6361:20020753

Research Note

Period behavior of the W Ursae Majoris contact binary AH Tauri

Yulan Yang and Qingyao Liu

National Astronomical Observatories, Chinese Academy of Sciences, China Yunnan Observatory, Chinese Academy of Sciences, Kunming, Yunnan Province, China United Laboratory of Optical Astronomy, Chinese Academy of Sciences, China

(Received 11 December 2001 / Accepted 29 April 2002 )

Abstract
New timing of minimum light determined from CCD observations of the W UMa type contact binary AH Tau is presented. From the present time of minimum light and those collected from the literature, the changes in the orbital period of the system are analyzed. The result reveals that the orbital period of AH Tau continuously decreased at a rate of $\frac{\Delta{p}}{p}=-1.4\times10^{-11}$ from 1944 to 1976 and suddenly and sharply decreased by about 0.33 s around 1976. After 1976 the orbital period of the system continually increased at a change rate of $\frac{\Delta {p}}{p}=1.5\times10^{-10}$ . A possible explanation of the changes in the orbital period of AH Tau is discussed. They may be the result of compound action of three mechanisms: the cyclical magnetic activity, the mass loss and the radius swelling of the two components of the system.


Key words: star: individual: AH Tau -- stars: binary: eclipsing

Offprint request: Yulan Yang, bily@public.km.yn.cn

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