Constraining black-hole binary spin precession and nutation with sequential prior conditioning

TL;DR

This paper explores the detectability of subtle spin effects in merging black-hole binaries using gravitational-wave data, employing a sequential prior conditioning method to improve parameter estimation and assess potential future detections.

Contribution

It introduces a sequential prior conditioning approach to better isolate weak spin effects like nutation and precession in gravitational-wave signals.

Findings

Current data do not show significant weak spin effects.

Future detections could enable constraints on spin nutations.

Method improves the extraction of subtle spin dynamics from gravitational-wave signals.

Abstract

We investigate the detectability of sub-dominant spin effects in merging black-hole binaries using current gravitational-wave data. Using a phenomenological model that separates the spin dynamics into precession (azimuthal motion) and nutation (polar motion), we present constraints on the resulting amplitudes and frequencies. We also explore current constraints on the spin morphologies, indicating if binaries are trapped near spin-orbit resonances. We dissect such weak effects from the signals using a sequential prior conditioning approach, where parameters are progressively re-sampled from their posterior distribution. This allows us to investigate whether the data contain additional information beyond what is already provided by quantities that are better measured, namely the masses and the effective spin. For the current catalog of events, we find no significant measurements of weak spin effects such as nutation and spin-orbit locking. We synthesize a source with a high nutational amplitude and show that near-future detections will allow us to place powerful constraints, hinting that we may be at the cusp of detecting spin nutations in gravitational-wave data.