Adiabatic inspirals under electromagnetic radiation reaction on Kerr spacetime

Abstract

A compact body in orbit about a black hole loses orbital energy and angular momentum through radiation-reaction processes, inspiralling toward the black hole until a final plunge. Here we consider a scenario with a charged compact body in which fluxes of electromagnetic radiation drive this inspiral. We calculate trajectories in the (p,e) plane for inspirals in the equatorial plane of a rotating black hole within the adiabatic (orbital-averaged-dissipative) approximation. We make comparisons with a nonrelativistic Keplerian approximation based on the Abraham-Lorentz force law, and with standard gravitational-wave driven scenarios. We find that EM-driven inspirals are less efficiently circularized (i.e. orbits remain more eccentric at the point of plunge) than their gravitational counterparts, and we quantify the effect of black hole spin. Published by the American Physical Society 2024