Binary Black Hole Encounters, Gravitational Bursts and Maximum Final Spin

TL;DR

This paper investigates how the residual orbital angular momentum in nonspinning black hole mergers influences the final black hole's spin, gravitational radiation, and burst patterns, revealing a maximum spin limit of approximately 0.78.

Contribution

It provides the first detailed analysis of the relationship between initial orbital angular momentum and the final black hole spin in nonspinning black hole mergers.

Findings

Final black hole spin parameter capping at ~0.78.

Maximum spin occurs at initial orbital angular momentum ~ M^2_h.

Multiple gravitational bursts observed in the merger process.

Abstract

The spin of the final black hole in the coalescence of nonspinning black holes is determined by the ``residual'' orbital angular momentum of the binary. This residual momentum consists of the orbital angular momentum that the binary is not able to shed in the process of merging. We study the angular momentum radiated, the spin of the final black hole and the gravitational bursts in a series of orbits ranging from almost direct infall to numerous orbits before infall that exhibit multiple bursts of radiation in the merger process. We show that the final black hole gets a maximum spin parameter $a/M_h \le 0.78$, and this maximum occurs for initial orbital angular momentum $L \approx M^2_h$.