Coincident morphological transitions in precessing black-hole binaries

TL;DR

This paper investigates simultaneous morphological transitions in precessing black-hole binaries, providing analytical characterizations and numerical confirmations, with implications for gravitational-wave observations.

Contribution

It introduces a systematic analysis of concurrent spin morphology transitions within the same precession cycle, expanding understanding of black-hole binary dynamics.

Findings

All coincident transitions can be analytically mapped and characterized.

Numerical integrations confirm the analytical results.

Such transitions correspond to extreme spin configurations with potential observational signatures.

Abstract

We present new insights into the phenomenology of post-Newtonian spin precession in black-hole binaries. Using multi-timescale methods, previous work has shown that the precession and nutation dynamics in such systems can be classified into so-called spin morphologies --mutually exclusive regions that partition the configuration space and characterize the motion of the black-hole spins relative to the binary's angular momentum. Radiation reaction can induce secular transitions between different morphology classes, which are generic occurrences during the inspiral of black-hole binaries. In this contribution, we systematically explore a more restrictive class of solutions in which multiple morphological transitions occur concurrently, i.e., within the same precession cycle. We find that all such cases can be mapped and characterized analytically, and we confirm these findings through numerical integrations. These coincident transitions correspond to extreme spin configurations in black-hole binaries with potential observational signatures in gravitational-wave astronomy.