A Systematic Study of Resonance-Driven Flux Modifications in Extreme-Mass-Ratio Inspirals

Abstract

Transient orbital resonances can introduce phase-dependent corrections to the evolution of extreme-mass-ratio inspirals (EMRIs), potentially altering their long-term dynamics and emitted gravitational-wave signals. In this work, we quantify the resonance-induced modifications to the energy, axial angular momentum, and Carter constant fluxes and compute the corresponding resonance coefficients across a broad region of the orbital parameter space. Using the publicly available \texttt{pybhpt} code, we solve the Teukolsky equation in the frequency domain to coherently combine the degenerate radial and polar harmonics that arise at resonance. We analytically derive a selection rule governing the relative radial-polar phase dependence of the resonant flux modifications. We argue that the relative strengths of different resonances reflect a balance between symmetry-induced cancellations and the degree to which the resonant orbit samples the underlying two-dimensional orbital phase space. For the dynamically important $3{:}2$ and $2{:}1$ resonances, we also characterize how the resonance coefficients vary with the primary black-hole spin, orbital eccentricity and inclination. Our results constitute the largest set of Teukolsky-based resonance coefficients calculated to date and provide essential input for future studies of transient orbital resonances in EMRIs.