Hybrid model for inspiral-merger-ringdown gravitational waveforms from comparable-mass, nonspinning binary black holes

TL;DR

This paper presents a hybrid analytical model combining post-Newtonian, black-hole perturbation, and effective-one-body theories to accurately simulate gravitational waveforms from nonspinning binary black hole mergers, achieving high fidelity with numerical relativity results.

Contribution

The authors develop a refined hybrid approximation method that improves waveform accuracy by integrating effective-one-body and phenomenological modifications, matching numerical relativity waveforms within 0.1% error for mass ratios 1 to 8.

Findings

Achieved waveform matches with numerical relativity within 0.1% error.

Extended the hybrid model to nonspinning binaries with mass ratios up to 8.

Demonstrated improved modeling of late inspiral, merger, and ringdown phases.

Abstract

Gravitational waves from comparable-mass binary-black-hole mergers are often described in terms of three stages: inspiral, merger and ringdown. Post-Newtonian and black-hole perturbation theories are used to model the inspiral and ringdown parts of the waveform, respectively, while the merger phase has been modeled most accurately using numerical relativity (NR). Nevertheless, there have been several approaches used to model the merger phase using analytical methods. In this paper, we adapt a hybrid approximation method that applies post-Newtonian and black-hole perturbation theories at the same times in different spatial regions of a binary-black-hole waveform (and which are matched at a boundary region with prescribed dynamics). Prior work with the hybrid method used leading post-Newtonian theory and the perturbation theory of nonrotating black holes, which led to errors during the late inspiral and disagreement with the dominant quasinormal-mode frequency extracted from NR simulations during the ringdown. To obtain a better match with NR waveforms of binary-black-hole mergers, we made several phenomenological modifications to the hybrid method. Specifically, to better capture the inspiral dynamics, we use the effective-one-body method for modeling the trajectory of the boundary between the two spatial regions. The waveform is determined by evolving a Regge-Wheeler-Zerilli-type equation for an effective black-hole perturbation theory problem with a modified Poschl-Teller potential. By tuning the potential to match the dominant quasinormal-mode frequency of the remnant black hole and also optimizing the boundary data on the matching region, we could match NR waveforms from nonspinning, comparable-mass binary black holes with mass ratios between one and eight, with a relative error of order $10^{-3}$.