Detection of a White Dwarf companion to a Blue Straggler Star in the
  outskirts of globular cluster NGC 5466 with the Ultraviolet Imaging Telescope
  (UVIT)
  We report the discovery of a hot white dwarf (WD) companion to a blue
straggler star (BSS) in the globular cluster (GC) NGC 5466, based on
observations from the Ultra-Violet Imaging Telescope (UVIT) on board AstroSat.
The Spectral Energy Distribution (SED) of the Far-UV detected BSS NH 84 was
constructed by combining the flux measurements from 4 filters of UVIT, with
GALEX, GAIA and other ground-based observations. The SED of NH 84 reveals the
presence of a hot companion to the BSS. The temperature and radius of the BSS
(T$_{\mathrm{eff}} = 8000^{+1000}_{-250}$ K, R/R$_\odot = 1.44 \pm 0.05$)
derived from Gemini spectra and SED fitting using Kurucz atmospheric models are
consistent with each other. The temperature and radius of the hotter companion
of NH 84 (T$_{\mathrm{eff}} = 32,000 \pm 2000$ K, R/R$_\odot = 0.021 \pm
0.007$) derived by fitting Koester WD models to the SED suggest that it is
likely to be a hot WD. The radial velocity derived from the spectra along with
the proper motion from GAIA DR2 confirms NH 84 to be a kinematic member of the
cluster. This is the second detection of a BSS-WD candidate in a GC, and the
first in the outskirts of a low density GC. The location of this BSS in NGC
5466 along with its dynamical age supports the mass-transfer pathway for BSS
formation in low density environments.
