Formation of a rotating hole from a close limit head-on collision

TL;DR

This paper models the formation of a rotating Kerr black hole from a close limit head-on collision of two rotating black holes, providing new waveforms and radiation features.

Contribution

It introduces a new solution to Einstein's equations for axisymmetric Kerr-hole formation from small-separation initial data.

Findings

Waveforms are linear in initial separation at small distances.

Waveforms exhibit damped oscillations with mixed quasinormal modes.

Results extend understanding of rotating black hole formation in collisions.

Abstract

Realistic black hole collisions result in a rapidly rotating Kerr hole, but simulations to date have focused on nonrotating final holes. Using a new solution of the Einstein initial value equations we present here waveforms and radiation for an axisymmetric Kerr-hole-forming collision starting from small initial separation (the ``close limit'' approximation) of two identical rotating holes. Several new features are present in the results: (i) In the limit of small separation, the waveform is linear (not quadratic) in the separation. (ii) The waveforms show damped oscillations mixing quasinormal ringing of different multipoles.