Binary black hole mergers: large kicks for generic spin orientations

TL;DR

This paper reports on simulations of equal-mass black hole mergers with high spins, showing that generic spin orientations typically produce large recoil velocities exceeding 1000 km/s, with a maximum of 2500 km/s.

Contribution

The study demonstrates that large recoil velocities are common in black hole mergers with arbitrary spin orientations, expanding understanding of merger dynamics.

Findings

Most mergers produce kicks over 1000 km/s

Maximum kick velocity observed is 2500 km/s

Large kicks are likely for generic spin configurations

Abstract

We present results from several simulations of equal mass black holes with spin. The spin magnitudes are $S/m^2=0.8$ in all cases, but we vary the spin orientations arbitrarily, in and outside the orbital plane. We find that in all but one case the final merged black hole acquires a kick of more than 1000 km/s, indicating that kicks of this magnitude are likely to be generic and should be expected for mergers with general spin orientations. The maximum kick velocity we find is 2500 km/s and occurs for initial spins which are anti-aligned in the initial orbital plane.