One Channel to Rule…Some of Them?Constraining the Origins of Binary Black-Hole Mergers with GWTC-3

The third Gravitational-Wave Transient Catalog (GWTC-3) updates the previous catalog (GWTC-2.1) with signals from the second half of the third observing run (O3b), bringing the total number of confident (False Alarm Rate < 1) detections to 76. These signals originate from mergers of compact object binary systems, primarily binary black hole (BBH) systems, whose astrophysical origin remains relatively unconstrained. We investigate the origins of BBH mergers with the analysis of Zevin et. al (2011.10057), who inferred the branching fractions between five BBH formation channels via Bayesian hierarchical analysis of GWTC-2. While the inclusion of data from O3b affects the inferred underlying and detectable branching fractions, the result that BBH mergers originate from multiple formation channels remains robust. Finally, we investigate potential biases by examining the effect of excluding various channels from this analysis on the recovered branching fractions.