The variations in light and color curves and possible short period oscillations of the binary AU Serpentis ^*

¹ Department of Astronomy, Nanjing University, Nanjing 210093, China
² Yunnan Observatory, Kunming 650011, China

Send offprint request to: Zong-yun Li, e-mail: zyli@nju.edu.cn

Received: 11 August 1997
Accepted: 26 January 1998

Abstract

We have photometrically monitored AU Ser for five years. It is considered to be a binary in poor thermal contact (Kaluzny 1986) or in detachment (Djurasevic 1993). The addition of new minimum times slightly modified the light ephemeris of Binnendijk (1972). The value and sign of the O'Connell effect have been changing with time. A remarkable variation of the difference between minimum depths in light curves has taken place in the period from 1991 to 1995. These variations in light curves are not expected by TRO theory but reminiscent of the situation in VW Cep. Our data, along with Binnendijk's, show a variation in color curves especially for 1995 observations. The variations in light and color curves might be straightforwardly explained by the distortion of starspot(s). Possible oscillations with short periods and shortly coherent times have been detected, which is unusual for such a binary.