A New Census of the variable star population in the Globular Cluster NGC 2419

TL;DR

This study provides a comprehensive catalog of 101 variable stars in NGC 2419, including new discoveries, analyzes their pulsation properties, and estimates the cluster's distance and metallicity.

Contribution

It presents the first extensive CCD light curves for a large sample of variables in NGC 2419, including 60 new discoveries, and derives key cluster parameters.

Findings

RR Lyrae properties suggest Oosterhoff type II classification

Distance to NGC 2419 estimated at 87.5 kpc

Cluster metallicity determined as [Fe/H] = -2.1

Abstract

We present B, V and I CCD light curves for 101 variable stars belonging to the globular cluster NGC2419, 60 of which are new discoveries, based on datasets obtained at the TNG, SUBARU and HST telescopes. The sample includes 75 RR Lyrae stars (of which 38 RRab, 36 RRc and one RRd), one Population II Cepheid, 12 SX Phoenicis variables, 2 DeltaScuti stars, 3 binary systems, 5 long-period variables, and 3 variables of uncertain classification. The pulsation properties of the RR Lyrae variables are close to those of Oosterhoff type II clusters, consistent with the low metal abundance and the cluster horizontal branch morphology,disfavoring (but not totally ruling out) an extragalactic hypotesis for the origin of NGC2419. The observed properties of RR Lyrae and SX Phoenicis stars are used to estimate the cluster reddening and distance, using a number of different methods. Our final value is mo(NGC2419)=19.71+/-0.08mag (D= 87.5+/-3.3kpc), with E(B-V)=0.08+/-0.01mag, [Fe/H]=-2.1dex in the Zinn & West metallicity scale, and a value of Mv that sets mo(LMC)=18.52mag. This value is in good agreement with most recent literature estimates of the distance to NGC 2419.