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General Relativity and Quantum Cosmology, gr-qc, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE,High Energy Physics - Phenomenology, hep-ph,High Energy Physics - Theory, hep-th
Abstract:
Ultralight scalar fields around spinning black holes can trigger superradiant
instabilities, forming a long-lived bosonic condensate outside the horizon. We
use numerical solutions of the perturbed field equations and astrophysical
models of massive and stellar-mass black hole populations to compute, for the
first time, the stochastic gravitational-wave background from these sources.
The background is observable by Advanced LIGO and LISA for field masses $m_s$
in the range $[2\times 10^{-13}, 10^{-12}]\,{\rm eV}$ and $[5\times 10^{-19},
5\times 10^{-16}]\,{\rm eV}$, respectively, and it can affect the detectability
of resolvable sources. Our estimates suggest that current constraints on the
stochastic background from LIGO O1 may already exclude masses in the Advanced
LIGO window. Semicoherent searches with Advanced LIGO (LISA) should detect
$\sim 15~(5)$ to $200~(40)$ resolvable sources for scalar field masses $3\times
10^{-13}$ ($10^{-17}$) eV. LISA measurements of massive BH spins could either
rule out bosons in the range $[10^{-18}, 1.6\times 10^{-13}]$ eV, or measure
$m_s$ with ten percent accuracy in the range $[10^{-17}, 10^{-13}]$ eV.
