TAPIR Seminar

In person and online -- to Join via Zoom

https://caltech.zoom.us/j/89695722750

Among the discoveries in LIGO/Virgo/KAGRA's third observing run are a handful of compact binary coalescences (CBCs) that stand out for one reason or another -- exceptional either because they were the first entry in a previously undetected class of CBCs, or because of the mass, mass ratio, or spins of their component compact objects. After briefly discussing the implications of these observations and their merger rates, I will focus on the tension that has arisen from the discovery of the most massive binaries in the LVK gravitational-wave catalogs. These binaries have component black holes encroaching on the pair-instability mass gap, where black holes are not expected to be formed directly from stars. I'll discuss an alternate formation channel, where massive black holes are assembled dynamically through repeated binary black hole mergers, and an analysis that constructs a binary black hole population that accounts for this "hierarchical formation" and allows us to identify potential hierarchical mergers in gravitational-wave catalogs.