An Updated Census of RR~Lyrae Stars in the Globular Cluster $\omega$~Centauri (NGC\,5139)

Abstract

[ABRIDGED] $\omega$ Centauri (NGC 5139) contains large numbers of variable stars of different types and, in particular, more than a hundred RR Lyrae stars. We have conducted a variability survey of $\omega$ Cen in the NIR, using ESO's 4.1m Visible and Infrared Survey Telescope for Astronomy (VISTA). This is the first paper of a series describing our results. $\omega$ Cen was observed using VIRCAM mounted on VISTA. A total of 42 and 100 epochs in $J$ and $K_{\mathrm{S}}$, respectively, were obtained, distributed over a total timespan of 352 days. PSF photometry was performed, and periods of the known variable stars were improved when necessary using an ANOVA analysis. An unprecedented homogeneous and complete NIR catalogue of RR Lyrae stars in the field of $\omega$ Cen was collected, allowing us to study, for the first time, all the RR Lyrae stars associated to the cluster, except 4 located far away from the cluster center. Membership status, subclassifications between RRab and RRc subtypes, periods, amplitudes, and mean magnitudes were derived for all the stars in our sample. Additionally, 4 new RR Lyrae stars were discovered, 2 of them with high probability of being cluster members. The distribution of $\omega$ Cen stars in the Bailey (period-amplitude) diagram is also discussed. Reference lines in this plane, for both Oosterhoff type I (OoI) and II (OoII) components, are provided. In the present paper, we clarify the status of many (candidate) RR Lyrae stars that had been unclear in previous studies. This includes stars with anomalous positions in the color-magnitude diagram, uncertain periods or/and variability types, and possible field interlopers. We conclude that $\omega$ Cen hosts a total of 88 RRab and 101 RRc stars, for a grand total of 189 likely members. We confirm that most RRab stars in the cluster belong to an OoII component, as previously found using visual data.

A\&A, in press

References in corpus (10)

• The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
• The Luminosities and Distance Scales of Type II Cepheid and RR Lyrae variables
• The period-luminosity relation for type II Cepheids in globular clusters
• New Metallicities of RR Lyrae Stars in omega Centauri: Evidence for a Non He-Enhanced Metal-Intermediate Population
• The infrared JHK light curves of RR Lyr
• A Deep Wide-Field Variable Star Catalog of Omega Centauri
• The VVV Templates Project. Towards an Automated Classification of VVV Light-Curves. I. Building a database of stellar variability in the near-infrared
• A Spectroscopic Survey for Omega Centauri Members at and beyond the Cluster Tidal Radius
• Searching for tidal tails around $\omega$ Centauri using RR Lyrae Stars
• The anomalous Cepheid XZ Ceti

Cited by in corpus (13)

• On the RR Lyrae stars in globulars: IV. $\omega$ Centauri Optical UBVRI Photometry
• TESS observations of Cepheid stars: first light results
• High-precision distance measurements with classical pulsating stars
• Near-Infrared Variability Study of the Central 2.3 arcmin x 2.3 arcmin of the Galactic Centre II. Identification of RR Lyrae Stars in the Milky Way Nuclear Star Cluster
• On the separation between RR Lyrae and Type II Cepheids and their importance for distance determination: the case of $\omega$ Cen
• Blazhko modulation in the infrared
• New type II Cepheids from VVV data towards the Galactic center
• Near-infrared Census of RR Lyrae variables in the Messier 3 globular cluster and the Period--Luminosity Relations
• APOGEE view of the globular cluster NGC 6544
• VVV catalog of ab-type RR Lyrae in the inner Galactic bulge
• The first Baade-Wesselink analysis of Blazhko RR Lyrae stars: discrepancies between photometrically and spectroscopically determined radius variations
• The VMC Survey -- LIV. Anomalous Cepheids in the Magellanic Clouds Period-Luminosity relations in the near-infrared bands
• Pulsating stars in $\omega$ Centauri: Near-IR properties and period-luminosity relations