Spin flips in generic black hole binaries

TL;DR

This paper investigates the complex spin dynamics, including flips and precession, of black holes in binary systems through numerical simulations and post-Newtonian analysis, revealing potential observational signatures.

Contribution

It introduces detailed numerical simulations and analytic formulas for spin flip phenomena in black hole binaries, extending understanding to unequal mass systems.

Findings

Black hole spins can undergo complete flips relative to the orbital plane.

The spin flip phenomenon extends to unequal mass binaries.

Analytic expressions approximate maximum flip angles and frequencies.

Abstract

We study the spin dynamics of individual black holes in a binary system. In particular we focus on the polar precession of spins and the possibility of a complete flip of spins with respect to the orbital plane. We perform a full numerical simulation that displays these characteristics. We evolve equal mass binary spinning black holes for $t=20,000M$ from an initial proper separation of $d=25M$ down to merger after 48.5 orbits. We compute the gravitational radiation from this system and compare it to 3.5 post-Newtonian generated waveforms finding close agreement. We then further use 3.5 post-Newtonian evolutions to show the extension of this spin {flip-flop} phenomenon to unequal mass binaries. We also provide analytic expressions to approximate the maximum {flip-flop} angle and frequency in terms of the binary spins and mass ratio parameters at a given orbital radius. Finally we discuss the effect this spin {flip-flop} would have on accreting matter and other potential observational effects.