A Comprehensive Catalog of Variable Stars in the Field of 47 Tucanae

Abstract

We present the results of a comprehensive search for stellar variability in the globular cluster 47 Tucanae. Using the Mount Stromlo 40 inch (1 m) telescope at Siding Spring Observatory and a combined V + R filter, we have detected 100 variable stars across a 52′ × 52′ field centered on the cluster. The main aim of this project is to search for transiting "hot Jupiter" planets in this cluster, the results of which shall be discussed in a separate paper. Here we present the V + R light curves and preliminary investigations of the detected variable stars, which comprise 28 eclipsing binaries (21 contact binaries and 7 detached systems), 45 RR Lyrae stars (41 of which belong to the Small Magellanic Cloud and 4 seemingly to the Galactic halo), and 20 K-giant long-period variables (LPVs). We also detected four δ Scuti stars, one type I Cepheid, and one type II Cepheid. One variable appears to be a possible dust-enshrouded SMC star with a short-period pulsation. Of these 100 variables, 69 are new discoveries. Our eclipsing binary sample indicates a clear radial segregation in period and includes two binaries that are seemingly orbited by low-luminosity stellar companions. One RR Lyrae star shows a Blazhko effect with remarkable regularity. Those variables previously known are cross-identified with a study by Kaluzny and coworkers. In agreement with previous studies, this work shows that the relative frequency of detectable variable stars (particularly contact binaries) in 47 Tuc is very low compared to other studied regions. Distance moduli of 18.93 ± 0.24 for the Small Magellanic Cloud and 13.14 ± 0.25 for 47 Tuc have been estimated from our sample and are in agreement with values previously published. The total database presented here contains V and / photometry for 43,067 47 Tuc field stars (13.0 ≤ V ≤ 21.0), along with 33 night V + R light curves and astrometry for 109,866 stars (14.5 ≤ V ≤ 22.5).