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Astron. Astrophys. 348, 795-799 (1999)

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Variable stars in the open cluster Mel 71

S.-L. Kim, B.-G. Park and M.-Y. Chun

Korea Astronomy Observatory, Taejon, 305-348, Korea (slkim@boao.re.kr)

Received 4 March 1999 / Accepted 22 June 1999


The UBVI and time-series CCD photometric observations of the intermediate-age open cluster Mel 71 were carried out to search for variable stars and obtain their physical parameters. By fitting the ZAMS to the observed color-color and color-magnitude diagrams, we estimated a reddening value of the cluster E(B-V) = 0.20 [FORMULA] 0.05 and a distance modulus (V-MV)[FORMULA] = 11.6 [FORMULA] 0.2. We also found its age of about log t = 9.0 from an isochrone fitting method for Z = 0.008.

Using the observed time-series data, we carefully examined light variations of 358 stars, fainter than [FORMULA]. Four [FORMULA] Sct stars and one eclipsing binary were discovered. They are located in the [FORMULA] Sct instability strip of the color-magnitude diagram. Incidence of variability within the instability strip is about 7%. Newly found [FORMULA] Sct stars show complex light variations, implying that they have multiple pulsation frequencies. The period of the binary star is estimated to be about [FORMULA].

Key words: Galaxy: open clusters and associations: individual: Mel 71 – stars: variables: ffi Sct – stars: binaries: eclipsing

Send offprint requests to: S.-L. Kim

© European Southern Observatory (ESO) 1999

Online publication: August 13, 199