AstroSat UVIT Detections of Chandra X-ray Sources in M31
  An ultraviolet survey of M31 has been carried out during 2017-19 with the
UVIT instrument onboard the AstroSat Observatory. Here we match the M31 UVIT
source catalog (Leahy et al. 2020) with the Chandra source catalog (Vulic et
al. 2016). We find 67 UVIT/Chandra sources detected in a varying number of UV
and X-ray bands. The UV and X-ray photometry is analyzed using powerlaw and
blackbody models. The X-ray types include 15 LMXBs and 5 AGNs. Cross-matches
with catalogs of stars, clusters and other source types yield the following. 20
of the UVIT/Chandra sources match with M31 globular clusters and 9 with
foreground stars. 3 more globular clusters and 2 more foreground stars are
consistent with the UVIT source positions although outside the Chandra match
radius of 1 arcsec. The UV emission of the UVIT/Chandra sources associated with
globular clusters is consistent with emission from blue horizontal branch stars
rather than from the X-ray source. The LMXBs in globular clusters are among the
most luminous globular clusters in M31.Comparison with stellar evolutionary
tracks shows that the UVIT/Chandra sources with high UV blackbody temperatures
are consistent with massive (10 to 30 M$_{\odot}$) stars in M31.
