X-ray Binaries and Star Clusters in the Antennae: Optical Cluster
  Counterparts
  We compare the locations of 82 X-ray binaries (XRBs) detected in the merging
Antennae galaxies by Zezas et al., based on observations taken with the Chandra
X-Ray Observatory, with a catalog of optically selected star clusters presented
by Whitmore et al., based on observations taken with the Hubble Space
Telescope. Within the 2 sigma positional uncertainty of 0.58", we find 22 XRBs
are coincident with star clusters, where only 2-3 chance coincidences are
expected. The ages of the clusters were estimated by comparing their UBVI,
Halpha colors with predictions from stellar evolutionary models. We find that
14 of the 22 coincident XRBs (64%) are hosted by star clusters with ages of 6
Myr or less. Five of the XRBs are hosted by young clusters with ages 10-100
Myr, while three are hosted by intermediate age clusters with 100-300 Myr.
Based on the results from recent N-body simulations, which suggest that black
holes are far more likely to be retained within their parent clusters than
neutron stars, we suggest that our sample consists primarily of black hole
binaries with different ages.
