Detection of White Dwarf Companions to Blue Straggler Stars from UVIT
  Observations of M67
  We investigate the old open cluster M67 using ultraviolet photometric data of
Ultra-Violet Imaging Telescope in multi-filter far-UV bands. M67, well known
for the presence of several blue straggler stars (BSS), has been put to
detailed tests to understand their formation pathways. Currently, there are
three accepted formation channels: mass transfer due to Roche-lobe overflow in
binary systems, stellar mergers either due to dynamical collisions or through
coalescence of close binaries. So far, there had not been any confirmed
detection of a white dwarf (WD) companion to any of the BSSs in this cluster.
Here, we present the detection of WD companions to 5 bright BSSs in M67. The
multiwavelength spectral energy distributions covering 0.12 -11.5 $\mu$m range,
were found to require binary spectral fits for 5 BSSs, consisting of a cool
(BSS) and a hot companion. The parameters (Luminosity, Temperature, Radius and
Mass) of the hot companions suggest them to be WDs with mass in the range 0.2 -
0.35 M$_{\odot}$ with T$_{eff}$ $\sim$ 11000 - 24000 K.
