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Astron. Astrophys. 348, 789-794 (1999)


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Search for variable stars in the open cluster NGC 7654

H.S. Choi 1,2, S.-L. Kim 2, Y.H. Kang 3 and B.-G. Park 1,2

1 Department of Astronomy and Atmospheric Sciences, Kyungpook National University Taegu, 702-701, Korea
2 Korea Astronomy Observatory, Taejon, 305-348, Korea (slkim@boao.re.kr)
3 Department of Earth Science Education, Kyungpook National University, Taegu, 702-701, Korea

Received 14 April 1999 / Accepted 25 June 1999

Abstract

Time-series CCD photometry of the open cluster NGC 7654 was performed over five nights from October 2nd to 18th, 1997 U.T., in order to search for new variable stars. We also carried out UBV photometric observations to obtain physical parameters of variable stars in the cluster.

We have derived the distance modulus of [FORMULA] = 10.9 [FORMULA] 0.2 and the interstellar reddening of [FORMULA] = 0.62 [FORMULA] 0.05 by fitting the ZAMS to the observed color-color and color-magnitude diagrams of the cluster. Using the theoretical isochrones with solar metal abundance by Bertelli et al. (1994), an age of the cluster, [FORMULA] = 8.0, was estimated.

Applying the ensemble normalization technique to the observed 1215 time-series data, light variations of 284 stars, fainter than [FORMULA] in the observed field, were carefully examined. As a result, three slowly pulsating B stars and one eclipsing binary were discovered in the cluster. We also confirmed the light variation of a low amplitude [FORMULA] Sct star which has been recently discovered by Viskum et al. (1997).

Key words: Galaxy: open clusters and associations: individual: NGC 7654 – stars: variables: general – stars: binaries: eclipsing

Send offprint requests to: S.-L. Kim

© European Southern Observatory (ESO) 1999

Online publication: August 13, 199

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