A Deep Wide-Field Variable Star Catalog of Omega Centauri

Abstract

We present a variable star catalog of an extensive ground-based wide-field variability survey in the globular cluster omega Centauri. Using the ANU 40-inch (1m) telescope at Siding Spring Observatory, the cluster was observed with a 52'x52' (0.75 deg^2) field for 25 nights. A total of 187 variable stars were identified in the field, 81 of which are new discoveries. This work comprises the widest field variability survey yet undertaken for this cluster. Here we present the V+R lightcurves and preliminary analysis of the detected variable stars, comprising 58 eclipsing binaries, 69 RR Lyrae stars, 36 long period variables (P>=2d) and 24 miscellaneous pulsators including 15 SX Phoenicis stars and two Type II Cepheids. Analysis of the eclipsing binary radial distribution has revealed an apparent lack of binaries in the 8'-15' range, perhaps indicating two separate binary populations. Four detached binaries have short periods (<2.5d) and are likely composed of low-mass M-dwarf components, useful for testing stellar evolution models. One further detached system has a period of 0.8 days and due to the blueness of the system could be composed of white dwarf stars. Analysis of the RR Lyrae sample has produced a reddening corrected distance modulus (also accounting for metallicity spread) for the cluster of 13.68+-0.27, a result consistent with previously published values. This paper also presents a total stellar database comprising V and I photometry (with astrometry better than 0.25'') for 203,892 stars with 12.0<V<21.0 and 25-night V+R lightcurves for 109,726 stars (14.0<V<22.0) for both the cluster and the field.

33 pages, 20 figures, accepted for publication in AJ. Full resolution version (pdf) can be found at http://www.mpia.de/homes/weldrake/weldrake.pdf

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