Population Analysis of High Mass X-Ray Binaries as Binary Black Hole Progenitors

Merging binary black holes (BBHs), as observed by the Laser Interferometer Gravitational–Wave Observatory (LIGO) and the Virgo Interferometer, undergo a high mass X–ray binary (HMXB) phase during their binary evolution. However, there are no well–constrained X–ray observations of HMXBs that are predicted to be likely progenitors of BBH mergers. In this project, we seek to quantify the relationships between HMXB and BBH populations in order to explain this discrepancy in observations. We use the Compact Object Synthesis and Monte–Carlo Investigation Code (COSMIC) to obtain representative local (z ≤ q 0.05) and Universe (z ≤ q 20) populations of binaries. We find that all merging BBHs in both populations evolve from HMXB progenitors. We show that detectable LIGO–Virgo sources and detectable HMXBs originate from populations of stellar binaries with different redshift and metallicity distributions. We also incorporate observability to calculate the probability that an observable HMXB will become a merging BBH in the future. Our results demonstrate that observational selection effects for both HMXB and BBH populations, in addition to differences in stellar evolution and environment, heavily contribute to the discrepancies found in observations.