The variable stars in the compact halo globular cluster NGC 5634 visited again

Abstract

We present new time-series CCD \emph{VR} photometry of the globular cluster NGC 5634. We aim to use the known RR Lyrae stars, members of the cluster, as indicators of mean metallicity and distance. Accurate coordinates, periods and an identification chart of the variables in the field of our images are provided. A membership analysis was performed, based on $Gaia$-DR3 proper motions, for 3525 point sources within 15 arcmin from the cluster center. The membership status for each known variable was established and it was found that V10, V11 and V16 are most likely field stars. The variability of the RRab star V7, considered non-variable for a number of years, is demonstrated. Via the Fourier decomposition of the light curves of cluster member RR Lyrae, the mean metallicity and distance were calculated independently from RRab and RRc stars to find [Fe/H]$_{\rm ZW}= -1.67 \pm 0.11$ y $D=23.9 \pm 0.8$ kpc, and [Fe/H]$_{\rm ZW}= -1.69 \pm 0.22$ y $D=22.9 \pm 1.0$ kpc respectively.