Ultraviolet Imaging Telescope (UVIT) observation of the Galactic Globular Cluster NGC 7492

Abstract

We present detailed photometric observations of the Galactic globular cluster NGC 7492 using the data obtained with two far-ultraviolet (FUV: 1300 - 1800 Å) and three near-ultraviolet (NUV: 2000 - 3000 Å) filters of Ultraviolet Imaging Telescope (UVIT) on-board the \textit{AstroSat} satellite. We confirmed the cluster membership of the extracted sources using GAIA data release 2 (Gaia DR2) proper motion data. We have used color-magnitude diagrams (CMDs) using UVIT and GAIA filters to separate out different evolutionary stages of the stars present in the cluster. We have identified a new extreme horizontal branch (EHB) star at the core of the cluster using UV and UV-optical CMDs. The estimated distance-modulus of the cluster is $16.95\pm 0.05$ obtained by fitting BaSTI isochrones with cluster parameters, $[Fe/H]=-1.8$ dex and age $=12.0$ Gyr on the V $-$ I vs V CMD. Interestingly, only the EHB star and blue horizontal branch stars (BHBs) among the UV-bright hot sources are detected in FUV filters of UVIT. We have derived the effective temperature of BHBs using color-temperature relation and spectral energy distributions (SEDs) of multi-band filters, which are in the range from 8,000 K to 10,500 K. We find a variation of He abundance of BHBs by fitting the BaSTI ZAHB. The range in the He abundance of the BHBs corresponding to the best fit isochrones is 0.247 to 0.350. We have estimated various physical parameters of the newly identified EHB star in the cluster using SED fit and post-HB evolutionary tracks. We have studied the radial distribution of all the sources of the cluster detected in UVIT. The sources detected in FUV filters extend beyond the half light radius (1.15${}^{\prime }$) of the cluster, whereas the sources detected in NUV filters extend beyond the tidal radius (9.2${}^{\prime }$) of the cluster.

arXiv commentAccepted for publication in MNRAS main journal

References in corpus (56)

• Gaia Data Release 2. Summary of the contents and survey properties
• A 3D Dust Map Based on Gaia, Pan-STARRS 1 and 2MASS
• The Pan-STARRS1 Surveys
• Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• New Grids of ATLAS9 Model Atmospheres
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• Mean proper motions, space orbits and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data
• Origin of the system of globular clusters in the Milky Way
• Variable Stars in Galactic Globular Clusters
• Ultraviolet Radiation from Evolved Stellar Populations -- I. Models
• The formation and assembly history of the Milky Way revealed by its globular cluster population
• The Updated BaSTI Stellar Evolution Models and Isochrones: I. Solar Scaled Calculations
• Proper motions and dynamics of the Milky Way globular cluster system from Gaia DR2
• In-orbit Calibrations of the Ultra-Violet Imaging Telescope
• Mass and shape of the Milky Way's dark matter halo with globular clusters from Gaia and Hubble
• Accreted versus In Situ Milky Way Globular Clusters
• Chemical Abundances and Rotation Velocities of Blue Horizontal-Branch Stars in Six Globular Clusters
• Helium enhanced stars and multiple populations along the horizontal branch of NGC2808: direct spectroscopic measurements
• Additional Calibration of the Ultra-Violet Imaging Telescope on board AstroSat
• Homogeneous photometry VII. Globular clusters in the Gaia era
• The peculiar Horizontal Branch of NGC 2808
• Ultra Violet Imaging Telescope (UVIT) on ASTROSAT
• The Horizontal Branch in the UV Colour Magnitude Diagrams. II. The case of M3, M13 and M79
• Outer density profiles of 19 Galactic globular clusters from deep and wide-field imaging
• The helium content of globular clusters: NGC6121 (M4)
• A search for stellar tidal debris of defunct dwarf galaxies around globular clusters in the inner Galactic halo
• UV Properties of Galactic Globular Clusters with GALEX II. Integrated colors
• UV Properties of Galactic Globular Clusters with GALEX I. The Color-Magnitude Diagrams
• Outer Versus Inner Halo Globular Clusters: NGC 7492 Abundances
• The globular cluster system of the Milky Way: accretion in a cosmological context
• In-orbit Performance of UVIT on ASTROSAT
• The discovery of tidal tails around the globular cluster NGC 7492 with Pan-STARRS1
• Variable stars in the globular cluster NGC 7492. New discoveries and physical parameters determination
• Hot UV-bright stars of galactic globular clusters
• Near-infrared integrated spectra of Galactic globular clusters: testing simple stellar population models
• Mass Segregation and Tidal Tails of the Globular Cluster NGC 7492
• A MegaCam Survey of Outer Halo Satellites. I. Description of the Survey
• The stellar content of the Hamburg/ESO survey. III. Field horizontal-branch stars in the Galaxy
• Photometric Selection of QSO Candidates From GALEX Sources
• Investigating the In-Flight Performance of the UVIT Payload on ASTROSAT
• The Horizontal Branch population of NGC 1851 as revealed by the Ultra-violet Imaging Telescope (UVIT)
• Extraction of globular clusters members with Gaia DR2 astrometry
• Spatial Distribution of Globular Clusters in the Galaxy
• UVIT-HST-GAIA view of NGC 288: A census of hot stellar population and their properties from UV
• Investigation of the Globular Cluster NGC 2808 with the Ultra-Violet Imaging Telescope
• G2C2 I: Homogeneous SDSS photometry for Galactic GCs
• Tests & Calibration on Ultra Violet Imaging Telescope (UVIT)
• The realm of the Galactic globular clusters and the mass of their primordial clouds
• The globular cluster NGC7492 and the Sagittarius tidal stream: together but unmixed
• The temperature distribution of horizontal branch stars: methods and first results
• On the star formation efficiencies and evolution of multiple stellar generations in Globular Clusters
• Chemical composition of UV-bright star ZNG 4 in the globular cluster M13
• Post-AGB Stars in Globular Clusters and Galactic Halos
• UVIT Observations of UV-Bright Stars in four Galactic Globular Clusters

Cited by in corpus (6)

• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• Globular Clusters UVIT Legacy Survey (GlobULeS) I. FUV-optical Color-Magnitude Diagrams for Eight Globular Clusters
• UVIT study of UV bright stars in the globular cluster NGC 4147
• Study of UV bright sources in globular cluster NGC 4590 using Ultraviolet Imaging Telescope (UVIT) observations
• Globular Cluster UVIT Legacy Survey (GlobULeS) $-$ II. Evolutionary status of hot stars in M3 and M13
• The AstroSat Observatory