# Blue Supergiant X-ray Binaries in the Nearby Dwarf Galaxy IC 10

## TL;DR

This study identifies and analyzes blue supergiant X-ray binaries in the galaxy IC 10, revealing an overabundance of these systems which are crucial for understanding gravitational wave progenitors and binary evolution.

## Contribution

It introduces a novel statistical correlation method to identify blue supergiant X-ray binaries in IC 10, providing new insights into their population and significance.

## Key findings

- 42 X-ray sources have optical counterparts in IC 10.
- 16 blue supergiant X-ray binaries identified with significant overabundance.
- Blue SG-XRBs are key progenitors for double-degenerate binaries and gravitational wave sources.

## 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.