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FSR 1716: A New Milky Way Globular Cluster Confirmed Using VVV RR Lyrae Stars

Minniti, Dante, Palma, Tali, Dékány, István, Hempel, Maren, Rejkuba, Marina, Pullen, Joyce, Alonso-Garcia, Javier, Barbá, Rodolfo, Barbuy, Béatriz, Bica, Eduardo, and others. (2017) FSR 1716: A New Milky Way Globular Cluster Confirmed Using VVV RR Lyrae Stars. The Astrophysical Journal Letters, 838 (1). ISSN 2041-8205. E-ISSN 2041-8213. (doi:10.3847/2041-8213/838/1/L14)

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https://doi.org/10.3847/2041-8213/838/1/L14

Abstract

We use deep multi-epoch near-IR images of the VISTA Variables in the Vía Láctea (VVV) Survey to search for RR Lyrae stars toward the Southern Galactic plane. Here, we report the discovery of a group of RR Lyrae stars close together in VVV tile d025. Inspection of the VVV images and PSF photometry reveals that most of these stars are likely to belong to a globular cluster that matches the position of the previously known star cluster FSR 1716. The stellar density map of the field yields a >100? detection for this candidate globular cluster that is centered at equatorial coordinates R.A. J2000 = 16:10:30.0, decl. J2000 = ?53:44:56 and galactic coordinates l = 329.77812, b = ?1.59227. The color–magnitude diagram of this object reveals a well-populated red giant branch, with a prominent red clump at K s = 13.35 ± 0.05, and J ? K s = 1.30 ± 0.05. We present the cluster RR Lyrae positions, magnitudes, colors, periods, and amplitudes. The presence of RR Lyrae indicates an old globular cluster, with an age >10 Gyr. We classify this object as an Oosterhoff type I globular cluster, based on the mean period of its RR Lyrae type ab, $\langle P\rangle =0.540$ days, and argue that this is a relatively metal-poor cluster with [Fe/H] = ?1.5 ± 0.4 dex. The mean extinction and reddening for this cluster are ${A}_{{K}_{s}}=0.38\pm 0.02$ and E(J ? K s ) = 0.72 ± 0.02 mag, respectively, as measured from the RR Lyrae colors and the near-IR color–magnitude diagram. We also measure the cluster distance using the RR Lyrae type ab stars. The cluster mean distance modulus is (m ? M)0 = 14.38 ± 0.03 mag, implying a distance D = 7.5 ± 0.2 kpc and a Galactocentric distance R G = 4.3 kpc.

Item Type: Article
DOI/Identification number: 10.3847/2041-8213/838/1/L14
Uncontrolled keywords: Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Dirk Froebrich
Date Deposited: 10 Mar 2017 09:54 UTC
Last Modified: 29 May 2019 18:48 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/60835 (The current URI for this page, for reference purposes)
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