Searching for continuous gravitational waves from axion clouds around black holes

Abstract

The recent gravitational-wave detections of binary mergers 
have opened a new and exciting window into observing the Universe. 
Persistent sources of gravitational waves must also exist; searches for 
continuous gravitational-wave signals generally look for signals from 
non-axisymmetric neutron stars, but are also suitable for continuous 
gravitational waves from axion annihilations in clouds around black 
holes. I will discuss the expected axion annihilations signal from an 
astrophysical standpoint, starting from the Galactic isolated black hole 
population.