CCD photometric study of the contact binary FG Hydrae^*

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

Send offprint request to: Y. Yang

Received: 21 October 1999
Accepted: 21 March 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.