Mergers of nonspinning black-hole binaries: Gravitational radiation characteristics

TL;DR

This paper provides a comprehensive analysis of gravitational waveforms from nonspinning black-hole binary mergers across various mass ratios, introducing a unified interpretation and a predictive model for late-time waveforms.

Contribution

It offers the first detailed, complete waveform descriptions including all multipolar components and introduces a novel implicit rotating source interpretation and a new effective-one-body waveform model.

Findings

Identified consistent relationships among $\,m=m$ modes across mass ratios.

Developed a predictive model for late-time waveforms based on frequency and amplitude evolution.

Provided detailed analytic fits for late-time frequency evolution.

Abstract

We present a detailed descriptive analysis of the gravitational radiation from black-hole binary mergers of nonspinning black holes, based on numerical simulations of systems varying from equal-mass to a 6:1 mass ratio. Our primary goal is to present relatively complete information about the waveforms, including all the leading multipolar components, to interested researchers. In our analysis, we pursue the simplest physical description of the dominant features in the radiation, providing an interpretation of the waveforms in terms of an {\em implicit rotating source}. This interpretation applies uniformly to the full wave train, from inspiral through ringdown. We emphasize strong relationships among the $\ell=m$ modes that persist through the full wave train. Exploring the structure of the waveforms in more detail, we conduct detailed analytic fitting of the late-time frequency evolution, identifying a key quantitative feature shared by the $\ell=m$ modes among all mass ratios. We identify relationships, with a simple interpretation in terms of the implicit rotating source, among the evolution of frequency and amplitude, which hold for the late-time radiation. These detailed relationships provide sufficient information about the late-time radiation to yield a predictive model for the late-time waveforms, an alternative to the common practice of modeling by a sum of quasinormal mode overtones. We demonstrate an application of this in a new effective-one-body-based analytic waveform model.