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.
@article{arxiv.gr-qc/9810080,
title = {Formation of a rotating hole from a close limit head-on collision},
author = {W. Krivan and R. H. Price},
journal= {arXiv preprint arXiv:gr-qc/9810080},
year = {2010}
}