Physical parameters of RR Lyrae stars in NGC 6171

Abstract

We present an analysis of VI CCD time-series photometry of the globular cluster NGC 6171. The main goal is to determine individual physical parameters for single-mode RR Lyrae stars present in the field of view of our images, by means of light curve Fourier decomposition and well-established calibrations and zero-points. This leads to the estimation of the mean values of the metallicity and distance for the parental cluster. From the RRab stars we find [Fe/H]ZW = -1.33 +- 0.12 and a distance d = 5.3 +- 0.3 kpc and from the RRc stars we find [Fe/H]ZW = -1.02 +- 0.19 and a distance d = 5.3 +- 0.2 kpc. Independent methods, such as the P-L relations for RRab and SX Phe stars enable the estimation of a weighted average distance to the cluster of 5.4 +- 0.1 kpc. We confirm the amplitude modulations of the Blazhko type of five RRab and the non-membership of V21 to the cluster. The colour-magnitude diagram is consistent with an age of 11 Gyrs. The distribution of RRab and RRc stars seems well segregated around the first overtone red edge of the instability strip. This positions NGC 6171 among OoI type clusters where the pulsating modes are neatly separated in the HB. We report two new irregular variables of the Lb type.

arXiv comment13 pages, 8 figures, accepted on October 4, 2018

References in corpus (23)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Intrinsic iron spread and a new metallicity scale for Globular Clusters
• Homogeneous Photometry for Star Clusters and Resolved Galaxies. II. Photometric Standard Stars
• Variable Stars in Galactic Globular Clusters
• The RR Lyrae Period-Luminosity Relation. I. Theoretical Calibration
• Galactic Globular Cluster Relative Ages. II
• A multi-color and Fourier study of RR Lyrae variables in the globular cluster NGC 5272 (M3)
• Light and Motion in SDSS Stripe 82: The Catalogues
• The "Tip" of the Red Giant Branch as a distance indicator: results from evolutionary models
• Difference Image Analysis: Extension to a Spatially Varying Photometric Scale Factor and Other Considerations
• Isochrones for Old (> 5 Gyr) Stars and Stellar Populations. I. Models for $-2.4\le$ [Fe/H] $\le +0.6$, $0.25\le Y\le 0.33$, and $-0.4\le$ [$\alpha$\Fe] $\le +0.4$
• Particle-physics constraints from the globular cluster M5: Neutrino Dipole Moments
• The RR Lyrae variables and Horizontal Branch of NGC6656 (M22)
• [Fe/H] relations for c-type RR Lyrae Variables based upon Fourier Coefficients
• Exploring the variable stars in the globular cluster NGC5024 (M53): New RR Lyrae and SX Phoenicis stars
• Systematic Trends In Sloan Digital Sky Survey Photometric Data
• Chemical Abundances of the Leo II Dwarf Galaxy
• The metal abundance distribution of the oldest stellar component in the Sculptor dwarf spheroidal galaxy
• Variable stars in the Globular Cluster NGC 2808
• RR Lyrae stars and the horizontal branch of NGC 5904 (M5)
• A detailed census of variable stars in the globular cluster NGC 6333 (M9) from CCD differential photometry
• Revisiting the variable star population in NGC~6229 and the structure of the Horizontal Branch
• Chemical Abundances of Red Giant Stars in the Globular Cluster M107 (NGC 6171)

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• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
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