Physically consistent gravitational waveform for capturing beyond general relativity effects in the compact object merger phase

TL;DR

This paper introduces a physically consistent gravitational waveform model that captures deviations from general relativity during the merger phase of compact binary coalescences, enabling tests of gravity in strong-field regimes.

Contribution

The authors propose a perturbative, physically consistent waveform parameterization for deviations from GR applicable to the entire coalescence process, including the merger phase.

Findings

The waveform model includes energy and angular momentum losses due to beyond-GR effects.

Fisher analysis shows the model can detect deviations from GR.

Compatibility with Einstein-dilaton Gauss-Bonnet waveforms demonstrated.

Abstract

The merger phase of compact binary coalescences is the strongest gravity regime that can be observed. To test the validity of general relativity (GR) in strong gravitational fields, we propose a gravitational waveform parameterized for deviations from GR in the dynamical and nonlinear regime of gravity. Our fundamental idea is that perturbative modifications to a GR waveform can capture possible deviations in the merger phase that are difficult to model in a specific theory of gravity. One of notable points is that our waveform is physically consistent in the sense that the additional radiative losses of energy and angular momentum associated with beyond-GR modifications are included. Our prescription to ensure physical consistency in the whole coalescence process is expected to be applicable to any deviation from the standard model of compact binary coalescence, such as the extended models of gravity or the environmental effects of compact objects, as long as perturbative modifications are considered. Based on the Fisher analysis and the compatibility with Einstein-dilaton Gauss-Bonnet waveforms, we show that our parameterization is a physically-consistent minimal one that captures the deviations in the nonlinear regime.