4 Summary

By performing the UBVI CCD photometry of the open cluster NGC 2539, we derived a reddening value $E(B-V)=0.06 \pm 0.03$, a distance modulus $(V-M_{V})_{0}=10.2 \pm 0.1$ and an age $\log t = 8.8$ ($\sim$630 Myr). Seven new variable stars were discovered from the time-series observations in V-band. We classify five of them as eclipsing binary stars, one as a $\delta$ Scuti star and one as a possible field $\gamma$ Doradus star.

At present, it might be difficult to make clear what physical parameters such as age (Krisciunas & Patten 1999) or metallicity (Handler 1999) control $\gamma$ Doradus type variability. A Further photometric survey to search for $\gamma$ Doradus stars in open clusters with various physical parameters would be needed.

Acknowledgements

We appreciate the referee Dr. M. Geffert's valuable comments. We also thank Dr. Y.-J. Moon for his careful reading. This work was partially supported by the Ministry of Science and Technology Research Fund.