6 Summary

From our observations along with Binnendijk's (1972), we come to the following conclusions:

1.

The light curves of AU Ser show the VW Cep or SW Lac type variation in the following aspects: i) The variation and reversion of O'Connell effect. It is positive in 1969 and 1970, negative in 1991 and 1992, and positive again in 1995. and ii) The variation of difference between minimum depths. The difference is the smallest in 1992, while the largest in 1995.

2.

The color curves show variable dips around phases 0 and 0.5. The variation in light is accompanied by the variation in color. In 1995 observation these variations are particularly significant, where remarkable dimming and severe reddening simultaneously take place around primary minimum.

3.

The possible short period oscillations have been definitely detected in AU Ser on May 22 and marginally on May 23, 1995, which is unusual for such a binary.

The results reported reveal AU Ser to be a puzzling system.

Acknowledgements

We would like to thank our referee Dr. Kaluzny for his comments and helpful suggestions. Many thanks should be given to Optical Astronomy Lab., Chinese Academy of Science for scheduling the observations and providing travel grant. This work is supported by the grant 19733001 from the National Science Foundation of P.R. China.