The variable star population in the globular cluster NGC 6934

TL;DR

This study analyzes the variable star population in NGC 6934 using CCD photometry, estimating metallicity and distance, identifying new variables, and discussing pulsation modes and stellar properties.

Contribution

It provides new variable star identifications, detailed physical parameters, and insights into pulsation modes and stellar evolution in NGC 6934.

Findings

Estimated [Fe/H] around -1.45 for the cluster.

Distance of approximately 16 kpc from Earth.

Discovered 12 new variable stars of various types.

Abstract

We report an analysis of new $V$ and $I$ CCD time-series photometry of the globular cluster NGC 6934. Through the Fourier decomposition of the RR Lyrae light curves, the mean values of [Fe/H] and the distance of the cluster were estimated, we found; [Fe/H]$_{UVES}$=-1.48$\pm$0.14 and $d$=16.03$\pm$0.42 kpc, and [Fe/H]$_{UVES}$=-1.43$\pm$0.11 and $d$=15.91$\pm$0.39 kpc, from the calibrations of RRab and RRc stars respectively. Independent distance estimations from SX Phe and SR stars are also discussed. Individual absolute magnitudes, radii and masses are also reported for RR Lyrae stars. We found 12 new variables: 4 RRab, 3 SX Phe, 2 W Virginis (CW)and 3 semi-regular (SR). The inter-mode or "either-or" region in the instability strip is shared by the RRab and RRc stars. This characteristic, observed only in some OoI clusters and never seen in an OoII, is discussed in terms of mass distribution in the ZAHB.