The Effect of Starburst Metallicity on Bright X-Ray Binary Formation
  Pathways
  We investigate the characteristics of young (< 20 Myr) and bright (Lx > 1e36
erg/s) High-Mass X-ray Binaries (HMXBs) and find the population to be strongly
metallicity-dependent. We separate the model populations among two distinct
formation pathways: (1) systems undergoing active Roche Lobe Overflow (RLO),
and (2) wind accretion systems with donors in the (super)giant (SG) stage,
which we find to dominate the HMXB population. We find metallicity to primarily
affect the number of systems which move through each formation pathway, rather
than the observable parameters of systems which move through each individual
pathway. We discuss the most important model parameters affecting the HMXB
population at both low and high metallicities. Using these results, we show
that (1) the population of ultra-luminous X-Ray sources can be consistently
described by very bright HMXBs which undergo stable Roche Lobe overflow with
mild super-Eddington accretion and (2) the HMXB population of the bright
starburst galaxy NGC~1569 is likely dominated by one extremely metal-poor
starburst cluster.
