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