Echoes of Kerr-like wormholes

TL;DR

This paper investigates gravitational wave echoes from Kerr-like wormholes, proposing a method to construct echo waveforms based on quasinormal modes, and explores effects of rotation on these signals and their stability.

Contribution

It introduces an accurate method to generate echo waveforms from wormhole quasinormal modes and analyzes the impact of rotation on these signals and their stability.

Findings

Echoes are dominated by the wormhole's nearest quasinormal frequency.

Rotation introduces a potential plateau that affects quasinormal mode degeneracy.

Small angular momentum leads to fading late-time instabilities.

Abstract

Structure at the horizon scale of black holes would give rise to echoes of the gravitational wave signal associated with the post-merger ringdown phase in binary coalescences. We study the waveform of echoes in static and stationary, traversable wormholes in which perturbations are governed by a symmetric effective potential. We argue that echoes are dominated by the wormhole quasinormal frequency nearest to the fundamental black hole frequency that controls the primary signal. We put forward an accurate method to construct the echoes waveform(s) from the primary signal and the quasinormal frequencies of the wormhole, which we characterize. We illustrate this in the static Damour-Solodukhin wormhole and in a new, rotating generalization that approximates a Kerr black hole outside the throat. Rotation gives rise to a potential with an intermediate plateau region that breaks the degeneracy of the quasinormal frequencies. Rotation also leads to late-time instabilities which, however, fade away for small angular momentum.