Black-hole ringdown with templates capturing spin precession: a critical re-analysis of GW190521

TL;DR

This paper develops a new amplitude model that captures spin precession in black-hole ringdown signals and applies it to re-analyze GW190521, showing that precession causes systematic shifts in inferred parameters but no strong evidence for precession.

Contribution

It introduces a physics-informed precessing ringdown model and demonstrates its application to gravitational-wave data, advancing the analysis of black-hole mergers.

Findings

Precession induces modest shifts in inferred parameters.

No strong evidence for precession in GW190521 ringdown.

Feasibility of precessing ringdown modeling demonstrated.

Abstract

The ringdown phase of a binary black-hole merger provides a clean probe of strong-field gravity, as it can be modeled with minimal assumptions. The quasi-normal-mode frequencies encode the mass and spin of the Kerr black-hole remnant, while the mode excitation depends on the progenitor binary. In this paper, we implement a recently developed amplitude model that captures spin precession in a simulation-based inference pipeline that specifically targets ringdown signals. We present a critical re-analysis of GW190521 -- a short-duration, merger-dominated event with conflicting interpretations. Spin-aligned and precessing analyses at two ringdown start times show that precession induces modest but systematic shifts in inferred parameters and subdominant mode amplitudes, although such ringdown-only analyses provide no strong evidence for precession. Our results demonstrate the feasibility of physics-informed precessing ringdown modelling, paving the way for the identification of spin precession in gravitational-wave events using solely their ringdown stages, where waveform systematics are expected to be substantially less prominent.