Exact analytic photon escape cones and silhouettes for extremal Kerr
arXiv:2405.08875
Abstract
We exhibit exact analytic, fully explicit, photon escape cones and related silhouettes ("shadows") at arbitrary distance from the extremal Kerr black hole. In contrast to the situation for non-extremal Kerr, where one typically has to resort to either numerical and/or perturbative investigations, the situation for extremal Kerr is amenable to direct analytic investigation.
5 pages