A&A Supplement series, Vol. 122, May I 1997, 471-481
Received April 11; accepted July 23, 1996
J. Kaluzny - M. Kubiak - M. Szymanski - A. Udalski - W. Krzeminski - M. Mateo - K. Stanek
Send offprint request: J. Kaluzny
Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena, Chile
Department of Astronomy, University of Michigan, 821 Dennison Bldg., Ann Arbor, MI 48109-1090, U.S.A.
Princeton University Observatory, Peyton Hall, Princeton NJ 08544, U.S.A.
Three fields located close to the center of the globular cluster Cen were surveyed in a search for variable stars. We present V-band light curves for 32 periodic variables. This sample includes 10 SX Phe stars, 19 eclipsing binaries, and three likely spotted variables (FK Com or RS CVn type stars). Only 5 of these variables were previously known (including two objects reported in Paper I). All SX Phe stars and 8 eclipsing binaries from our sample belong to blue stragglers. Five binaries occupy positions on the upper main-sequence of the cluster and another four are located at the base of the subgiant branch. Of particular interest is detection of a detached binary system with a period P=4.64 day. Further study of this star can provide direct information about properties of turnoff stars in Cen. All SX Phe stars and most of eclipsing binaries discovered in our survey are likely cluster members. We present V vs. V-I color-magnitude diagrams for the monitored fields. A populous group of likely hot subdwarfs as well as numerous candidates for blue stragglers can be noted in these diagrams. Our data indicate that Cen possesses the largest number of blue stragglers among all galactic globulars.
keywords: globular clusters: individual: Cen -- star: variables: other -- blue stragglers -- binaries: eclipsing -- HR diagram