The Variable Star Population of the Globular Cluster B514 in the Andromeda Galaxy

Abstract

A rich harvest of RR Lyrae stars has been identified for the first time in B514, a metal-poor ([Fe/H] = 1.95 +/- 0.10 dex) globular cluster of the Andromeda galaxy (M31), based on Hubble Space Telescope Wide Field Planetary Camera 2 and Advanced Camera for Surveys time-series observations. We have detected and derived periods for 89 RR Lyrae stars (82 fundamental-mode -RRab- and 7 first-overtone -RRc- pulsators, respectively) among 161 candidate variables identified in the cluster. The average period of the RR Lyrae variables (<Pab> = 0.58 days and <Pc> = 0.35 days, for RRab and RRc pulsators, respectively) and the position in the period-amplitude diagram both suggest that B514 is likely an Oosterhoff type I cluster. This appears to be in disagreement with the general behaviour of the metal-poor globular clusters in the Milky Way, which show instead Oosterhoff type II pulsation properties. The average apparent magnitude of the RR Lyrae stars sets the mean level of the cluster horizontal branch at <V(RR)> = 25.18 +/- 0.02 (sigma=0.16 mag, on 81 stars). By adopting a reddening E(B-V) = 0.07 +/- 0.02 mag, the above metallicity and M_V=0.44 +/- 0.05 mag for the RR Lyrae variables of this metallicity, we derive a distance modulus of mu_0=24.52 +/- 0.08 mag, corresponding to a distance of about 800 +/- 30 kpc, based on a value of M_V that sets mu_0(LMC)=18.52.

ApJ Letters, in press

References in corpus (2)

• ACS photometry of newly-discovered globular clusters in the outer halo of M31
• The extended structure of the remote cluster B514 in M31. Detection of extra-tidal stars

Cited by in corpus (10)

• RR Lyrae variables: visual and infrared luminosities, intrinsic colours, and kinematics
• Clustering of Local Group distances: publication bias or correlated measurements? II. M31 and beyond
• RR Lyrae variables in M32 and the disk of M31
• Time-Series Photometry of Globular Clusters: M62 (NGC 6266), the Most RR Lyrae-Rich Globular Cluster in the Galaxy?
• The ancient stellar population of M32: RR Lyr Variable stars confirmed
• Dwarf spheroidal satellites of M31: I. Variable stars and stellar populations in Andromeda XIX
• Age and structure parameters of a remote M31 globular cluster B514 based on HST, 2MASS, GALEX and BATC observations
• Hide and seek between Andromeda's halo, disk, and giant stream
• Does the Oosterhoff Dichotomy Exist in The Andromeda Galaxy? I. The case of G11
• Variability search in M 31 using Principal Component Analysis and the Hubble Source Catalog