The influence of spin in black hole triplets

TL;DR

This study investigates how black hole spins affect the dynamics and outcomes of triplet systems through numerical simulations, revealing that spin can significantly alter system evolution and lifetimes, especially for intermediate-mass black holes.

Contribution

It introduces detailed simulations of black hole triplets including spin effects, highlighting the impact on system outcomes and lifetimes across various mass ranges.

Findings

12.9% of simulations changed outcomes after including spin.

Intermediate-mass black holes are most affected by spin.

Simulations evolve from 2D to 3D when spin is considered.

Abstract

Spin can influence the dynamics of the already chaotic black hole triplet system. We follow this problem in two sets of simulations: first, the Agekian-Anosova region (or region D), and second, using Pythagorean triangles. We use ARCcode, an N-body code that performs numerical integration of orbits. This code includes post-Newtonian corrections, which we include up to the 2.5th order. In set one of our simulations, we fix the masses of the black holes at 10$^{6}$ M$_{\odot}$. Then we run the simulations first without any spin added and after by initialising spin on one of the black holes. We find that after including spin into the system, 12.9% of the simulations changed outcomes. Either the systems went from having all black holes merging to having a black hole escaping the system, or vice versa. In the second set of simulations, we expanded into Pythagorean triangles as initial positions of black holes, stemming from Burrau's three-body problem. We varied the masses of the black holes from 10$^{0}$ M$_{\odot}$ to 10$^{12}$ M$_{\odot}$. Black holes in these systems were given spin in normalised units ranging from 0 to 0.95. We find that intermediate mass black holes in the range of 10$^{4}$ M$_{\odot}$-10$^{5}$ M$_{\odot}$, were influenced the most by spin, particularly in their lifetimes. We also find that simulations, initialised as 2D, become 3D.