RR Lyrae stars in the globular cluster Palomar 2

TL;DR

This study uses 11-year CCD imaging to identify and analyze RR Lyrae stars in Palomar 2, determining cluster membership, distance, metallicity, and confirming its Oosterhoff type.

Contribution

It provides new variable star identifications, refined cluster parameters, and confirms the Oosterhoff classification using Fourier analysis.

Findings

Identified 21 new RR Lyrae variables in Palomar 2.

Estimated cluster distance as 27.2 ± 1.8 kpc.

Determined metallicity as [Fe/H] = -1.39 ± 0.55.

Abstract

A CCD VI imaging time-series over 11-year is employed to explore the light curves of stars in the field of Palomar 2. We discovered 20 RRab and 1 RRc variables. A revision of Gaia-DR3 data enabled us to identify 10 more variables and confirm the RRab nature of 6 of them and one RGB. The cluster membership is discussed and 18 variables are most likely cluster members. The Fourier light curve decomposition for the 11 best quality light curves of cluster member stars leads to independent estimates of the cluster distance 27.2 +- 1.8 kpc and [Fe/H]ZW=-1.39 +- 0.55. We confirm the cluster as of the Oo I type.