Directed searches for gravitational waves from ultralight bosons
Gravitational-wave detectors can be used to search for yet-undiscovered ultralight bosons, including those conjectured to solve problems in particle physics, high-energy theory, and cosmology. In particular, ground-based instruments could probe boson masses between 10^(−15) eV and 10^(−11) eV, which are largely inaccessible to other experiments. In this paper, we explore the prospect of searching for the continuous gravitational waves generated by boson clouds around known black holes. We carefully study the predicted waveforms and use the latest-available numerical results to model signals for different black-hole and boson parameters. We then demonstrate the suitability of a specific method (hidden Markov model tracking) to efficiently search for such signals, even when the source parameters are not perfectly known as well as allowing for some uncertainty in theoretical predictions. We empirically study this method's sensitivity and computational cost in the context of boson signals, finding that it will be possible to target remnants from compact-binary mergers localized with at least three instruments. For signals from scalar clouds, we also compute detection horizons for future detectors (Advanced LIGO, LIGO Voyager, Cosmic Explorer, and the Einstein Telescope). Among other results, we find that, after one year of observation, an Advanced LIGO detector at design sensitivity could detect these sources up to over 100 Mpc, while Cosmic Explorer could reach over 10^4 Mpc. These projections offer a more complete picture than previous estimates based on analytic approximations to the signal power or idealized search strategies. Finally, we discuss specific implications for the follow-up of compact-binary coalescences and black holes in x-ray binaries. Along the way, we review the basic physics of bosons around black holes, in the hope of providing a bridge between the theory and data-analysis literatures.
© 2019 American Physical Society. Received 20 October 2018; published 26 April 2019. The authors thank Evan Hall for useful input regarding the sensitivities of present and future detectors. M. I. and R. B. thank Asimina Arvanitaki, Masha Baryakhtar, William East, and Robert Lasenby for organizing the meeting "Searching for New Particles with Black Hole Superradiance" held at the Perimeter Institute for Theoretical Physics . Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Economic Development & Innovation. M. I. and L. S. are members of the LIGO Laboratory. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation and operates under cooperative agreement PHY-0757058. Support for this work was provided by NASA through the NASA Hubble Fellowship Grant No. HST-HF2-51410.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under Contract No. NAS5-26555. L. S. was supported by an Australian Research Training Program Stipend Scholarship and the Albert Shimmins Fund at earlier stages of this project. The research was also supported by Australian Research Council (ARC) Discovery Project No. DP170103625 and the ARC Centre of Excellence for Gravitational Wave Discovery CE170100004. R. B. acknowledges financial support from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 792862. This paper carries LIGO Document No. LIGO-P1800270.
Submitted - 1810.03812.pdf
Erratum - PhysRevD.102.049901.pdf
Published - PhysRevD.99.084042.pdf