Non-Kerr Constraints using Binary Black Hole inspirals considering phase modifications up to 4 PN order

TL;DR

This paper tests the Kerr black hole hypothesis using gravitational wave data from binary black hole inspirals, focusing on phase modifications up to 4 PN order to constrain deviations from General Relativity.

Contribution

It introduces a theory-agnostic method to constrain non-Kerr deviations in gravitational wave signals considering phase modifications up to 4 PN order.

Findings

Constraints on deformation parameters $\alpha_{13}$ and $\epsilon_3$

Degeneracy between non-Kerr parameters

No significant deviation from Kerr spacetime

Abstract

The gravitational field around an astrophysical black hole (BH) is thought to be described by the Kerr spacetime, which is a solution of the Einstein equation. Signatures of binary black hole (BBH) coalescence in gravitational waves (GW) follow the Kerr spacetime as the theoretical foundation. Hence, any possible deviations from the Kerr spacetime around BHs serve as a test of the nature of gravity in the strong-field regime and of the predictions of General Relativity. In our study, we perform a theory-agnostic test of the Kerr hypothesis using BBH inspirals from the third Gravitational-wave Transient Catalog (GWTC-3). Considering the Johannsen metric, we compute the leading-order deviation to the emitted GW in the frequency domain. Our results provide constraints on two deformation parameters ($\alpha_{13}$ and $\epsilon_3$) and demonstrate the degeneracy between these two non-Kerr parameters.