Gravitational Atoms and Black Hole Binaries

Superradiant instabilities may create clouds of ultralight bosons around rotating black holes, forming so-called "gravitational atoms". In this talk, I will review a series of papers that study the effects of a binary companion’s presence. The companion can induce transitions between bound states of the cloud (resonances), as well as transitions from bound to unbound states (ionization). These processes backreact on the binary’s dynamics and leave characteristic imprints on the emitted gravitational waves (GWs), providing direct information about the mass of the boson and the state of the cloud. However, some of the resonances may destroy the cloud before the binary enters the frequency band of future gravitational wave detectors. This destruction leaves a mark on the binary’s eccentricity and inclination, which can be identified through a statistical analysis of a population of binary black holes.