Search for variable stars in the open cluster NGC 2539

¹ Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701, Korea
² Korea Astronomy Observatory, Daejeon 305-348, Korea
³ Department of Astronomy and Space Science, Sejong University, Seoul 143-747, Korea
⁴ Department of Earth Science, Pusan National University, Busan 609-735, Korea
⁵ Astronomy Program, SEES, Seoul National University, Seoul 151-742, Korea

Corresponding author: K. J. Choo, kjchoo@knu.ac.kr

Received: 17 July 2002
Accepted: 7 November 2002

Abstract

We present UBVI absolute and V-band time-series CCD photometric results for the intermediate-age open cluster NGC 2539. From the empirical zero-age main sequence and theoretical isochrone fitting in color-color and color-magnitude diagrams, we estimated the physical parameters of this cluster as follows: the color excess of , the distance modulus of and the age of (~630 Myr). By carefully examining the time-series images, we discovered seven new variable stars in the observed cluster field. Considering the light curves, periods and positions on the color-magnitude diagram, we classified them as five eclipsing binary stars, one δ Scuti star and one γ Doradus candidate. The γ Doradus candidate might not be a cluster member because it is located redder by about than the cool edge of γ Doradus instability strip.