Gravitational waves from plunges into Gargantua

TL;DR

This paper analytically derives gravitational waveforms from extreme mass ratio inspirals into nearly extremal Kerr black holes, revealing critical behavior and implications for gravitational wave detection.

Contribution

It introduces a closed-form analytical method for time domain waveforms of plunges into Kerr black holes using conformal symmetry, extending understanding of gravitational wave signals.

Findings

Waveforms feature a polynomial ringdown followed by exponential decay.

Critical behavior in waveform amplitude near the innermost stable orbit.

Extended LISA detection volume for near-critical and high angular momentum orbits.

Abstract

We analytically compute time domain gravitational waveforms produced in the final stages of extreme mass ratio inspirals of non-spinning compact objects into supermassive nearly extremal Kerr black holes. Conformal symmetry relates all corotating equatorial orbits in the geodesic approximation to circular orbits through complex conformal transformations. We use this to obtain the time domain Teukolsky perturbations for generic equatorial corotating plunges in closed form. The resulting gravitational waveforms consist of an intermediate polynomial ringdown phase in which the decay rate depends on the impact parameters, followed by an exponential quasi-normal mode decay. The waveform amplitude exhibits critical behavior when the orbital angular momentum tends to a minimal value determined by the innermost stable circular orbit. We show that either near-critical or large angular momentum leads to a significant extension of the LISA observable volume of gravitational wave sources of this kind.