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arXiv · 2608.28037

Devoured by a Hairy Gargantua: Probing Massive Scalar Charges with Non-minimal Curvature Coupling with Extreme-Mass-Ratio Inspirals

Leif Lui·Adrian Ka-Wai Chung·Alejandro Torres-Orjuela
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Abstract

Ultralight scalar fields nonminimally coupled to curvature can endow rotating black holes with stationary hair and alter nearby orbits. Using recently constructed hairy black-hole spacetimes, we model the transition to plunge of an extreme-mass-ratio inspiral. For scalar masses $\mu M=0.01$ and $0.1$ and dimensionless curvature coupling $\zeta=10^{-3},10^{-4}$, we find $\mathcal{O}(10)$ rad of gravitational-wave dephasing relative to general relativity over $\mathcal{O}(10^3)$ orbits. A multimode Fisher forecast at $\mu M=0.2$, where neighbouring hair solutions permit a numerical $\mu$-derivative, suggests that $\zeta$ and $\mu$ could be measured to precisions of $\simeq0.2\%$ and $0.6$--$1.1\%$, respectively, for a source with signal-to-noise ratio of about 80 in LISA.

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Leif Lui, Adrian Ka-Wai Chung, Alejandro Torres-Orjuela. 2026-08-28. Devoured by a Hairy Gargantua: Probing Massive Scalar Charges with Non-minimal Curvature Coupling with Extreme-Mass-Ratio Inspirals. https://arxiv.org/abs/2608.28037

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