\textit{Superradiance} can trigger the formation of an ultra-light boson cloud around a spinning black hole. Once formed, the boson cloud is expected to emit a nearly periodic, long-duration, gravitational-wave signal. For boson masses in the range (10−13−10−11) eV, and stellar mass black holes, such signals are potentially detectable by gravitational wave detectors, like Advanced LIGO and Virgo. In this {\it Letter} we present full band upper limits for a generic all-sky search for periodic gravitational waves in LIGO O2 data, and use them to derive - for the first time - direct constraints on the ultra-light scalar boson field mass.
@article{arxiv.1909.08854,
title = {Direct constraints on ultra-light boson mass from searches for continuous gravitational waves},
author = {Cristiano Palomba and Sabrina D'Antonio and Pia Astone and Sergio Frasca and Giuseppe Intini and Iuri La Rosa and Paola Leaci and Simone Mastrogiovanni and Andrew L. Miller and Federico Muciaccia and Ornella J. Piccinni and Luca Rei and Francesco Simula},
journal= {arXiv preprint arXiv:1909.08854},
year = {2022}
}