New Faint Variable Stars in the Outer Regions of the Metal-rich Globular Cluster M71

Abstract

Sixteen photometric variable stars with mean V magnitudes between 15.2 and 20.3 have been discovered in a 167 × 167 field centered on the metal-rich globular cluster M71. The identifications are the result of a systematic time-series CCD imaging survey of the cluster using the Dominion Astrophysical Observatory 1.8 m telescope. Light curves and finding charts are presented for the newly identified stars (eight of which are definite variables, three probable, and five possible). These 16 stars, when combined with the seven faint variable stars discovered recently by Hodder et al. and Yan & Mateo, bring to 23 the number of faint variables now known in M71. The variable stars are of two basic types: W UMa– or Algol-like eclipsing binaries and SX Phoenicis radially pulsating variable blue straggler stars. Additional photometry is required to confirm the nature of the variability of several of the stars.