Inspirals from the innermost stable circular orbit of Kerr black holes: Exact solutions and universal radial flow
arXiv:2209.03579
Abstract
We present exact solutions of test particle orbits spiralling inward from the innermost stable circular orbit (ISCO) of a Kerr black hole. Our results are valid for any allowed value of the angular momentum -parameter of the Kerr metric. These solutions are of considerable physical interest. In particular, the radial 4-velocity of these orbits is both remarkably simple and, with the radial coordinate scaled by its ISCO value, universal in form, otherwise completely independent of the black hole spin.
Accepted for publication in Physical Review Letters. 5 pages 3 figures