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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 720070.0, MPI für Astronomie / Publikationen_mpia
Updated census of RR Lyrae stars in the globular cluster ω Centauri (NGC 5139)
Authors:Navarrete, C.; Contreras Ramos, R.; Catelan, M.; Clement, C. M.; Gran, F.; Alonso-García, J.; Angeloni, R.; Hempel, M.; Dékány, I.; Minniti, D.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:Astronomy and Astrophysics
Volume:577
Start Page:id. A99 (13 pp)
Audience:Not Specified
Abstract / Description:<BR /> Aims: ω Centauri (NGC 5139) contains many variable stars of different types and, in particular, more than one hundred RR Lyrae stars. This enabled gathering a homogeneous sample (in terms of instrument, image quality, and time coverage) of high-quality near-infrared (NIR) RR Lyrae light curves by performing an extensive time-series campaign aimed at this object. We have conducted a variability survey of ω Cen in the NIR, using ESO's 4.1 m Visible and Infrared Survey Telescope for Astronomy (VISTA). This is the first paper of a series describing our results. <BR /> Methods: ω Cen was observed using VIRCAM mounted on VISTA. A total of 42 epochs in J and 100 epochs in KS were obtained, distributed over a total timespan of 352 days. Point-spread function photometry was performed using DAOPHOT in the inner and DoPhot in the outer regions of the cluster. Periods of the known variable stars were improved when necessary using an ANOVA analysis. <BR /> Results: We collected an unprecedented homogeneous and complete NIR catalog of RR Lyrae stars in the field of ω Cen, allowing us to study for the first time all the RR Lyrae stars associated with the cluster, except for four stars that are located far away from the cluster center. We derived membership status, subclassifications between RRab and RRc subtypes, periods, amplitudes, and mean magnitudes for all the stars in our sample. Additionally, four new RR Lyrae stars were discovered, two of which are very likely cluster members. We also discuss here the distribution of ω Cen stars in the Bailey (period-amplitude) diagram. We provide reference lines in this plane for both Oosterhoff Type I (OoI) and Oosterhoff Type II (OoII) components in J and KS. <BR /> Conclusions: We clarify the status of many (candidate) RR Lyrae stars that have been reported as 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 ω Cen hosts a total of 88 RRab and 101 RRc stars, which makes for a grand total of 189 probable members. We confirm that most RRab stars in the cluster appear to belong to an OoII component, as previously found using visual data. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, with the VISTA telescope (project ID 087.D-0472, P.I. R. Angeloni).Appendices are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201424838/olm">http://www.aanda.org</A>
Free Keywords:stars: variables: RR Lyrae; stars: variables: general; globular clusters: individual: ωCentauri; infrared: stars; surveys; stars: horizontal-branch
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-6361
URL:http://cdsads.u-strasbg.fr/abs/2015A%26A...577A..9...
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