Variable stars in the VVV globular clusters. I. 2MASS-GC02 and Terzan10

Abstract

The VISTA Variables in the Via Lactea (VVV) ESO Public Survey is opening a new window to study the inner Galactic globular clusters using their variable stars. These globular clusters have been neglected in the past due to the difficulties caused by the presence of an elevated extinction and high field stellar densities in their lines of sight. However, the discovery and study of any present variables in these clusters, especially RRLyrae stars, can help to greatly improve the accuracy of their physical parameters. It can also help to shed some light on the interrogations brought by the intriguing Oosterhoff dichotomy in the Galactic globular cluster system. In a series of papers we plan to explore the variable stars in the globular clusters falling inside the field of the VVV survey. In this first paper we search and study the variables present in two highly-reddened, moderately metal-poor, faint, inner Galactic globular clusters: 2MASS-GC02 and Terzan10. We report the discovery of sizable populations of RR Lyrae stars in both globular clusters. We use near-infrared period-luminosity relations to determine the color excess of each RR Lyrae star, from which we obtain both accurate distances to the globular clusters and the ratios of the selective to total extinction in their directions. We find the extinction towards both clusters to be elevated, non-standard, and highly differential. We also find both clusters to be closer to the Galactic center than previously thought, with Terzan10 being on the far side of the Galactic bulge. Finally, we discuss their Oosterhoff properties, and conclude that both clusters stand out from the dichotomy followed by most Galactic globular clusters.

arXiv commentAccepted for publication in AJ

References in corpus (31)

• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way
• Variable Stars in Galactic Globular Clusters
• VVV DR1: The First Data Release of the Milky Way Bulge and Southern Plane from the Near-Infrared ESO Public Survey VISTA Variables in the Via Lactea
• Interstellar Extinction Law toward the Galactic Center III: J, H, Ks bands in the 2MASS and the MKO systems, and 3.6, 4.5, 5.8, 8.0 micron in the Spitzer/IRAC system
• Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
• A Trend Filtering Algorithm for wide field variability surveys
• A Comparison of Elemental Abundance Ratios in Globular Clusters, Field Stars, and Dwarf Spheroidal Galaxies
• The RR Lyrae Period-Luminosity Relation. I. Theoretical Calibration
• Interstellar Extinction Law in the J, H, and Ks Bands toward the Galactic Center
• Near-IR properties of 24 Globular Clusters in the Galactic Bulge
• VVV Survey Near-Infrared Photometry of Known Bulge RR Lyrae stars: the Distance to the Galactic Center and Absence of a Barred Distribution of the Metal-Poor Population
• NGC 6441: another indication for a very high helium content in Globular Cluster stars
• The Luminosities and Distance Scales of Type II Cepheid and RR Lyrae variables
• Uncloaking globular clusters in the inner Galaxy
• Variable Stars in the Unusual, Metal-Rich Globular Cluster NGC 6388
• Theoretical insights into the RR Lyrae K-band Period-Luminosity relation
• HST Snaphot Study of Variable Stars in Globular Clusters: Inner Region of NGC 6441
• RR Lyrae Stars in NGC 6388 and NGC 6441: A New Oosterhoff Group?
• Discovery of VVV CL001. A Low-Mass Globular Cluster Next to UKS~1 in the Direction of the Galactic Bulge
• Variable Stars in the Unusual, Metal-Rich Globular Cluster NGC 6441
• Discovery of New Milky Way Star Clusters Candidates in the 2MASS Point Source Catalog
• Cepheids and other short-period variables near the Galactic Centre
• RR Lyrae variables in Galactic globular clusters: IV. Synthetic HB and RR Lyrae predictions
• Serendipitous 2MASS Discoveries Near the Galactic Plane: A Spiral Galaxy and Two Globular Clusters
• An Aligned Stream of Low-Metallicity Clusters in the Halo of the Milky Way
• On the Origin of Bimodal Horizontal-Branches in Massive Globular Clusters: The Case of NGC 6388 and NGC 6441
• The Extinction Toward the Galactic Bulge from RR Lyrae Stars
• Image-Subtraction Photometry of Variable Stars in the Globular Clusters NGC 6388 and NGC 6441
• The VVV Templates Project. Towards an Automated Classification of VVV Light-Curves. I. Building a database of stellar variability in the near-infrared

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