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Astron. Astrophys. 350, 469-475 (1999)

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A photometric survey for variable stars in the globular cluster M5

J. Kaluzny 1,2, I. Thompson 3, W. Krzeminski 1,3 and W. Pych 2

1 Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
2 Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
3 Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA

Received 1 April 1999 / Accepted 20 July 1999


We present the results of a photometric survey for variable stars in the nearby globular cluster M5. A [FORMULA] arcmin field centered on the cluster was monitored for a total of 37 hours with a CCD camera mounted on the 1.0-m Swope telescope. Five new variables were identified: four blue stragglers which are SX Phe pulsating variables, and an eclipsing binary with an orbital period of 0.466 d. The eclipsing binary lies near the main-sequence turnoff on the cluster color-magnitude diagram. We do not confirm the variability of any of the 10 eclipsing binaries identified in the cluster field by Reid (1996) and Yan & Reid (1996). The dwarf nova M5-V101 exhibited two outbursts with full amplitudes of about 2.7 mag during our observations. A [FORMULA] color-magnitude diagram of the surveyed field was obtained, and a possible extreme HB star located 2 mag below cutoff of the blue HB was identified.

Key words: stars: Hertzsprung – Russel (HR) and C-M diagrams – Galaxy: globular clusters: individual: M5 – stars: variables: general – stars: blue stragglers – stars: binaries: eclipsing

Send offprint requests to: J. Kaluzny (jka@sirius.astrouw.edu.pl)

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© European Southern Observatory (ESO) 1999

Online publication: October 4, 1999