Unstable flip-flopping spinning binary black holes

TL;DR

This paper analyzes the flip-flop effect and anti-alignment instability in spinning binary black holes, providing analytic criteria for when these phenomena occur, which impacts gravitational wave data analysis and astrophysical modeling.

Contribution

It introduces a unified description of flip-flop and anti-alignment instability using flip-flop frequencies and maps the parameter space where the instability occurs.

Findings

Instability effective for mass ratios 0.5<q<1

Provides analytic expressions for instability regions

Impacts gravitational wave parameter estimation

Abstract

We give a unified description of the flip-flop effect in spinning binary black holes and the anti-alignment instability in terms of real and imaginary flip-flop frequencies. We find that this instability is only effective for mass ratios $0.5<q<1$. We provide analytic expressions that determine the region of parameter space for which the instability occurs in terms of maps of the mass ratio and spin magnitudes $(q,\alpha_1,\alpha_2)$. This restricts the priors of parameter estimation techniques for the observation of gravitational waves from binary black holes and it is relevant for astrophysical modeling and final recoil computations of such binary systems.