# Dynamic Signatures of Black Hole Binaries with Superradiant Clouds

## TL;DR

This paper explores how superradiant clouds around rotating black holes influence nearby objects' orbits, potentially detectable through gravitational waves, offering a new method to search for light bosons.

## Contribution

It investigates the impact of superradiant clouds on orbital dynamics and gravitational wave signals, highlighting enhanced capture rates and hierarchical mergers as novel observational signatures.

## Key findings

- Enhanced probability of black hole captures due to clouds.
- Orbital modulations detectable by LISA in gravitational wave signals.
- Potential to identify light bosons through gravitational wave observations.

## Abstract

Superradiant clouds may develop around a rotating black hole, if there is a bosonic field with Compton wavelength comparable to the size of the black hole. In this paper, we investigate the effects of the cloud on the orbits of nearby compact objects. In particular, we consider the dynamical friction and the backreaction due to level mixing. Under these interactions, the probability of a black hole dynamically capturing other compact objects, such as stellar mass black holes and neutron stars, is generally enhanced with the presence of the cloud. For extreme mass ratio inspirals and binary stellar mass binary black holes, the cloud-induced orbital modulation may be detected by observing the gravitational waveform using space borne gravitational wave detectors, such as LISA. Interestingly within certain range of boson Compton wavelength, the enhanced capture rate of stellar mass black holes could accelerate hierarchical mergers, with higher-generation merger product being more massive than the mass threshold predicted by supernova pair instability. These observational signatures provide promising ways of searching light bosons with gravitational waves.