Investigation of the Globular Cluster NGC 2808 with the Ultra-Violet Imaging Telescope

Abstract

Globular clusters represent stellar laboratories where observations can be used to validate models of stellar evolution. In this study, we put forth new ultraviolet (UV) photometric results of stars in the Galactic globular cluster NGC 2808. NGC 2808 is known to host multiple stellar populations that include at least four distinct groups of horizontal Branch (HB) stars. We have observed this cluster with the AstroSat-UltraViolet Imaging Telescope in two far-UV (FUV) and five near-UV (NUV) filters, respectively. These UV filters enable the identification of HB populations of stars. The results from four NUV filters exhibit bimodal distributions in magnitude histograms. The nature of bimodality has been investigated on the basis of distinct stellar types contributing to those bands. The color-magnitude diagrams constructed using FUV and NUV filters enable the location of hot stellar populations, viz. stars belonging to Red HB (RHB), Blue HB, Extreme HB, Blue Hook branch and post-Asymptotic Giant Branch. Prominent gaps are observed in the UV color-magnitude diagrams. We report for the first time, a photometric gap in a NUV color-magnitude diagram, that segregates the RHB population of this cluster into two groups, that are likely to be associated with distinct generations of stars. We have constructed and examined the GAIA color-magnitude diagram of the optical counterparts of the hot UV stars. We also investigate the spatial density distributions of various groups of stars in the cluster and comment on the proposed formation models of multiple populations.

13 pages, 11 figures, 2 tables, Accepted for publication in MNRAS

References in corpus (7)

• The Gaia mission
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• The radial distribution of blue straggler stars and the nature of their progenitors
• Na-O Anticorrelation and HB. VI. The chemical composition of the peculiar bulge globular cluster NGC 6388
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. X. The radial distribution of stellar populations in NGC 2808
• On the radial distribution of horizontal branch stars in ngc2808

Cited by in corpus (5)

• Hot UV-bright stars of galactic globular clusters
• The First Extensive Exploration of UV-bright Stars in the Globular Cluster NGC 2808
• Ultraviolet Imaging Telescope (UVIT) observation of the Galactic Globular Cluster NGC 7492
• Study of UV bright sources in globular cluster NGC 4590 using Ultraviolet Imaging Telescope (UVIT) observations
• A Wide View of the Galactic Globular Cluster NGC 2808: Red Giant and Horizontal Branch Star Spatial Distributions