Effects of dynamical capture on two equal-mass nonspinning black holes

TL;DR

This study uses numerical relativity simulations to analyze dynamical capture events of two equal-mass nonspinning black holes, revealing how initial conditions influence gravitational wave emissions and merger outcomes.

Contribution

The paper introduces a comprehensive numerical analysis of black hole dynamical captures, including an analytical model for gravitational-wave emission and a parametrization of the capture-merger transition.

Findings

Dependence of emission timing on incidence angle

Analytical fit for gravitational-wave emission

Identification of scattering versus capture angles

Abstract

Dynamical captures of black holes are unique events that provide an exceptional opportunity to probe the strong-field regime of gravitational physics. In this article, we perform numerical relativity simulations to study the events of dynamical capture of two equal-mass nonspinning black holes. We consider a suite of scenarios within a range of initial linear momenta ($p/M=0.095-0.75$) and incidence angles ($\theta=6.36^\circ-2.83^\circ$), and study the emitted Weyl scalar ($\Psi_4$) of each case, as well as the spins and masses of the black holes before and after they merge. We provide a simple analytical model which accurately fits the gravitational-wave emission. We study the dependence of the time interval between the capture and the merger emissions with respect to the incidence angle, which can be well parametrized by a first-order divergent behavior, allowing us to find the angle that separates a scattering event from a dynamical capture. We also find that, in general, the parameters that model the first emission can be well described by linear or exponentially decaying functions in terms of the incidence angle, while others display more complex behaviors that offer valuable insights into the nature of these events.