Publication date: Mar 2018
We construct the light escape cones of isotropic spot sources of
radiation residing in special classes of reference frames in the Kerr-de
Sitter (KdS) black hole spacetimes, namely in the fundamental class of
`non-geodesic‘ locally non-rotating reference frames (LNRFs), and two
classes of `geodesic‘ frames, the radial geodesic frames (RGFs), both
falling and escaping, and the frames related to the circular geodesic
orbits (CGFs). We compare the cones constructed in a given position for
the LNRFs, RGFs, and CGFs. We have shown that the photons locally
counter-rotating relative to LNRFs with positive impact parameter and
negative covariant energy are confined to the ergosphere region.
Finally, we demonstrate that the light escaping cones govern the shadows
of black holes located in front of a radiating screen, as seen by the
observers in the considered frames. For shadows related to distant
static observers the LNRFs are relevant.
Stuchlík, Zdeněk; Charbulák, Daniel; Schee, Jan;