Black Hole Spectroscopy for Precessing Binary Black Hole Coalescences

TL;DR

This paper investigates the quasinormal modes excited in the ringdowns of precessing binary black hole mergers, revealing that modes other than the dominant ones can be significant, which impacts black hole spectroscopy and gravitational wave analysis.

Contribution

It introduces a framework relating the ringdown modes of precessing and non-precessing systems, supported by numerical relativity data, and highlights the importance of additional modes in gravitational wave signals.

Findings

Precessing systems' ringdowns are similar to non-precessing ones up to a rotation.

Additional quasinormal modes like (2,±1) or (2,0) can dominate in precessing systems.

Results align with analysis of GW190521 and inform waveform modeling.

Abstract

The spectroscopic study of black hole quasinormal modes in gravitational-wave ringdown observations is hindered by our ignorance of which modes should dominate astrophysical signals for different binary configurations, limiting tests of general relativity and astrophysics. In this work, we present a description of the quasinormal modes that are excited in the ringdowns of comparable mass, quasi-circular precessing binary black hole coalescences -- a key region of parameter space that has yet to be fully explored within the framework of black hole spectroscopy. We suggest that the remnant perturbation for precessing and non-precessing systems is approximately the same up to a rotation, which implies that the relative amplitudes of the quasinormal modes in both systems are also related by a rotation. We present evidence for this by analyzing an extensive catalog of numerical relativity simulations. Additional structure in the amplitudes is connected to the system's kick velocity and other asymmetries in the orbital dynamics. We find that the ringdowns of precessing systems need not be dominated by the ${(\ell,m)=(2,\pm 2)}$ quasinormal modes, and that instead the $(2,\pm 1)$~or~$(2,0)$ quasinormal modes can dominate. Our results are consistent with a ringdown analysis of the LIGO-Virgo gravitational wave signal GW190521, and may also help in understanding phenomenological inspiral-merger-ringdown waveform model systematics.