APT1 - Astrophysical Black Holes |
Speaker_ |
Bozza, Valerio |
Talk _ |
Extreme Gravitational Lensing by Supermassive Black Holes |
Abstract _ |
Photons grazing a supermassive black hole experience large deflections that cannot be described in the weak field approximation. Such photons give rise to very faint additional images of any given source, which would show up just outside the apparent shadow of the black hole. We investigate the properties of these images through an analytical expansion of the deflection angle around the minimal impact parameter, showing that their positions and brightnesses are related to the parameters of the black hole and the gravitational theory used to describe it. We present estimates for the position and the luminosity of images for several kinds of potential sources orbiting around Sgr A*, which indeed represents an ideal candidate lens, discussing the technical requirements for their detection. In particular, we suggest that future space interferometry missions will be able to detect these elusive witnesses of the strong gravitational fields generated by black holes. References: gr-qc/0208075, astro-ph/0503664, gr-qc/0507137, gr-qc/0604093 |