Testing the Kerr nature with binary black hole inspirals

TL;DR

The paper addresses testing the Kerr nature of astrophysical black holes using strong-field gravitational-wave data from binary black hole inspirals. It maps deformations in three parametrized metrics—KRZ, Johannsen, and Simpson-Visser—onto modifications of the inspiral GW phase via the ppE framework, focusing on equatorial quasi-circular orbits with $a_* = 0$. From LVK GWTC-2 data, it derives constraints on deformation parameters $\delta_1$, $\delta_2$, $\alpha_{13}$, and $l^2$, finding results consistent with Kerr within uncertainties, with the strongest bound for the Simpson-Visser case coming from GW190707A. The work provides a general framework for metric-level tests of GR with GW observations and highlights the value of multi-messenger constraints for cross-checking potential deviations from Kerr.

Abstract

The theory of general relativity (GR) is the standard framework for the description of gravitation and the geometric structure of spacetime. With the recent advancement of observational instruments, it has become possible to probe the strong field regime to test GR. We present the constraints obtained from the binary black hole inspiral data of the LIGO-Virgo-Kagra (LVK) gravitational wave (GW) observations on the deformations of some popular parametrized non-Kerr metrics.

Figures (1)

• Figure 1: Constraints for $\alpha_{13}$ parameter of the Johannsen metric Johannsen:2013szh across X-ray, radio and GW measurements. Data from Refs. Bambi:2021chrshashank2022EventHorizonTelescope:2022xqjpsaltis2020gravitational.