Circularization and Final Spin in Eccentric Binary Black Hole Inspirals

TL;DR

This study uses numerical relativity to analyze how eccentricity affects the final spin and mass of black holes after binary mergers, revealing that binaries tend to circularize before merging, with maximum spins around 0.72.

Contribution

It provides detailed simulations of eccentric binary black hole mergers, showing the relationship between initial eccentricity and the final black hole's properties, including spin and mass.

Findings

Final spin a_f/M_f ≈ 0.69 for e < 0.4

Final mass M_f/M_adm ≈ 0.96 independent of e<0.4

Maximum spin a_f/M_f ≈ 0.72 around e ≈ 0.5

Abstract

We present results from numerical relativity simulations of equal mass, non-spinning binary black hole inspirals and mergers with initial eccentricities e <= 0.8 and coordinate separations D >= 12 M of up to 9 orbits (18 gravitational wave cycles). We extract the mass M_f and spin a_f of the final black hole and find, for eccentricities e < 0.4, that a_f/M_f = 0.69 and M_f/M_adm = 0.96 are independent of the initial eccentricity, suggesting that the binary has circularized by the merger time. For e > 0.5, the black holes plunge rather than orbit, and we obtain a maximum spin parameter a_f/M_f = 0.72 around e = 0.5.