Resonances as signatures of scalar clouds in eccentric extreme-mass-ratio inspirals

TL;DR

This paper investigates how eccentric orbits in extreme-mass-ratio inspirals into scalar clouds cause detectable resonances in scalar fluxes, affecting gravitational wave signals and aiding future detection.

Contribution

It introduces a fully relativistic analysis of eccentric EMRIs in scalar clouds, revealing new resonance phenomena absent in previous circular orbit studies.

Findings

Eccentricity induces dense resonances in scalar fluxes near the last stable orbit.

Resonances can cause detectable dephasing in gravitational waveforms.

Eccentricity enhances prospects for detecting EMRIs in scalar clouds with future detectors.

Abstract

We study eccentric extreme-mass-ratio inspirals (EMRIs) into scalar clouds formed through superradiant instabilities, within a fully relativistic perturbative framework. While previous relativistic analyses were limited to circular motion, we consider eccentric equatorial orbits around a Schwarzschild black hole and show that eccentricity induces a dense sequence of potentially detectable resonances in the scalar fluxes near the last stable orbit. The resonances we uncover only appear in a fully relativistic calculation, as they are intrinsically tied to the split between azimuthal and radial frequencies in the strong-field regime. By evolving the orbit adiabatically, we show that these resonances can induce detectable dephasing in the gravitational waveform. Our results demonstrate that eccentricity could play a decisive role in confidently detecting EMRIs embedded in scalar clouds with future space-based detectors.