The Transition from Inspiral to Plunge for a Compact Body in a Circular Equatorial Orbit Around a Massive, Spinning Black Hole

TL;DR

This paper provides an analytical description of the transition from inspiral to plunge for a compact body orbiting a spinning black hole, highlighting potential gravitational wave signals detectable by LISA.

Contribution

It introduces a new analytic model for the transition regime near the innermost stable circular orbit in Kerr spacetime.

Findings

Analytic expression for the transition regime derived.

Potential gravitational wave signals detectable by LISA.

Enhanced understanding of inspiral-plunge transition dynamics.

Abstract

There are three regimes of gravitational-radiation-reaction-induced inspiral for a compact body with mass mu, in a circular, equatorial orbit around a Kerr black hole with mass M>>mu: (i) The "adiabatic inspiral regime", in which the body gradually descends through a sequence of circular, geodesic orbits. (ii) A "transition regime", near the innermost stable circular orbit (isco). (iii) The "plunge regime", in which the body travels on a geodesic from slightly below the isco into the hole's horizon. This paper gives an analytic treatment of the transition regime and shows that, with some luck, gravitational waves from the transition might be measurable by the space-based LISA mission.