Title: Blue Supergiant X-ray Binaries in the Nearby Dwarf Galaxy IC 10,
Abstract: In young starburst galaxies, the X-ray population is expected to be dominated
by the relics of the most massive and short-lived stars, black-hole and
neutron-star high mass X-ray binaries (XRBs). In the closest such galaxy, IC
10, we have made a multi-wavelength census of these objects. Employing a novel
statistical correlation technique, we have matched our list of 110 X-ray point
sources, derived from a decade of Chandra observations, against published
photometric data. We report an 8 sigma correlation between the celestial
coordinates of the two catalogs, with 42 X-ray sources having an optical
counterpart. Applying an optical color-magnitude selection to isolate blue
supergiant (SG) stars in IC 10, we find 16 matches. Both cases show a
statistically significant overabundance versus the expectation value for chance
alignments. The blue objects also exhibit systematically higher fx/fv ratios
than other stars in the same magnitude range. Blue SG-XRBs include a major
class of progenitors of double-degenerate binaries, hence their numbers are an
important factor in modeling the rate of gravitational wave sources. We suggest
that the anomalous features of the IC 10 stellar population are explained if
the age of the IC 10 starburst is close to the time of the peak of interaction
for massive binaries.