Gravitational wave echoes from black holes in massive gravity

TL;DR

This paper explores how gravitational wave echoes from black holes with scalar hair in massive gravity can serve as observational tests for this alternative gravity theory.

Contribution

It demonstrates that coupling between gravitational perturbations and scalar hair in massive gravity alters black hole ringdown signals, producing detectable gravitational wave echoes.

Findings

Scalar hair affects quasinormal modes

Echoes can be produced in gravitational wave signals

Potential for testing massive gravity with observations

Abstract

Gravitational waves are rapidly becoming a very reliable tool for testing alternative theories of gravity. In particular, features in the gravitational wave emission during black hole ringdown phase provide a direct probe of the spacetime outside the black hole. In this article, we consider black holes in ghost-free massive gravity. These black holes generically have scalar hair. We found that a simple coupling between gravitational perturbations and this scalar hair can change the quasinormal ringing of the black hole, and in particular, produce echoes in the emitted gravitational waves. This finding provides a clear-cut way to test massive gravity theory using gravitational wave observations.