Final spin and radiated energy in numerical simulations of binary black holes with equal masses and equal, aligned or anti-aligned spins

TL;DR

This paper presents new numerical relativity simulations of equal-mass binary black holes with aligned or anti-aligned spins, providing improved formulas for the final spin and radiated energy to aid gravitational wave research.

Contribution

It introduces ten new simulations and combines them with previous data to develop more accurate analytic formulas for black hole merger outcomes.

Findings

Enhanced fitting formulas for final spin and radiated energy.

Simulations include the highest spin cases to date.

Results improve gravitational wave modeling accuracy.

Abstract

The behavior of merging black holes (including the emitted gravitational waves and the properties of the remnant) can currently be computed only by numerical simulations. This paper introduces ten numerical relativity simulations of binary black holes with equal masses and equal spins aligned or anti-aligned with the orbital angular momentum. The initial spin magnitudes have $|\chi_i| \lesssim 0.95$ and are more concentrated in the aligned direction because of the greater astrophysical interest of this case. We combine this data with five previously reported simulations of the same configuration, but with different spin magnitudes, including the highest spin simulated to date, $\chi_i \approx 0.97$. This data set is sufficiently accurate to enable us to offer improved analytic fitting formulae for the final spin and for the energy radiated by gravitational waves as a function of initial spin. The improved fitting formulae can help to improve our understanding of the properties of binary black hole merger remnants and can be used to enhance future approximate waveforms for gravitational wave searches, such as Effective-One-Body waveforms.