Astron. Astrophys. Suppl. Ser. 144, 457-461

CCD photometric study of the contact binary FG Hydrae

Y. Yang - Q. Liu

Send offprint request: Y. Yang

Yunnan Observatory, Chinese Academy of Sciences, Kunming, Yunnan Province, 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 October 21, 1999; accepted March 21, 2000

Abstract:

A new light curve of the contact binary FG Hya is presented in this paper. The new light curve and those obtained by other authors from 1955 to 1985 show the change in the shape of the light curves of the system. The difference in the depths between the primary and secondary eclipses increased yearly from 1955 to 1985, but the present light curve seems to exhibit the same shape as the light curve of Smith in 1955. The long-term decrease of the orbital period of the system may be clear if Mahdy et al.'s (1985) timings in question were counted out. The present light curve and those obtained by Binnendijk in 1962 and Yang et al. in 1982 are all analyzed by means of the latest version of the WD program. The results show that FG Hya is an over-contact binary with a small mass ratio. Although the light curves of the system changed considerably, the solutions of the light curves obtained in 1955, 1982 and 1999 are in agreement.

Key words: star -- binary -- light curve change -- period change -- photometric solutions