Inspiral-merger-ringdown waveforms in Einstein-scalar-Gauss-Bonnet gravity within the effective-one-body formalism

Abstract

Gravitational waves (GWs) provide a unique opportunity to test general relativity (GR) in the highly dynamical, strong-field regime. So far, the majority of the tests of GR with GW signals have been carried out following parametrized, theory-independent approaches. An alternative avenue consists in developing inspiral-merger-ringdown (IMR) waveform models in specific beyond-GR theories of gravity, by combining analytical and numerical-relativity results. In this work, we provide the first example of a full IMR waveform model in a beyond-GR theory, focusing on Einstein-scalar-Gauss-Bonnet (ESGB) gravity. This theory has attracted particular attention due to its rich phenomenology for binary black-hole (BH) mergers, thanks to the presence of nontrivial scalar fields. Starting from the state-of-the-art, effective-one-body (EOB) multipolar waveform model for spin-precessing binary BHs , we include theory-specific corrections to the EOB Hamiltonian, the metric and scalar energy fluxes, the GW modes, the quasinormal-mode (QNM) spectrum and the mass and spin of the remnant BH. We also propose a way to marginalize over the uncertainty in the merger morphology with additional nuisance parameters. Interestingly, we observe that changes in the frequency of the ringdown waveform due to the final mass and spin corrections are significantly larger than those due to ESGB corrections to the QNM spectrum. By performing Bayesian parameter estimation for the GW events GW190412, GW190814, and GW230529_181500, we place constraints on the fundamental coupling of the theory ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:msqrt> <a:mrow> <a:msub> <a:mrow> <a:mi>α</a:mi> </a:mrow> <a:mrow> <a:mi>GB</a:mi> </a:mrow> </a:msub> </a:mrow> </a:msqrt> <a:mo>≲</a:mo> <a:mn>0.31</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>km</a:mi> </a:mrow> </a:math> at 90% confidence). The bound could be improved by one order of magnitude by observing a single “golden” binary system with next-generation ground-based GW detectors. Our model can be used to improve constraints on modifications of GR with upcoming GW observations, and to provide forecasts for future GW detectors on the ground and in space.

Topics & Concepts