Sombras de Buracos Negros
Kerr BHs, which are BHs with rotation, are presently the most “standard” Black Hole (BH) solutions, and possibly also the most realistic ones. However, in order to provide alternative shadow templates for upcoming astronomical observations, namely for the observation of the supermassive BH candidate Sgr A* in the center of our galaxy by the Event Horizon Telescope, it is timely to also consider different types of solutions. Hence, a novel class of BHs in equilibrium with a massive scalar field, Kerr BHs with scalar hair, was considered. This class exhibits intriguing properties, some of which are shadows that differ significantly from the Kerr prediction. For an observer, a shadow is a BH’s apparent shape in the sky due to gravitational lensing of nearby radiation, emitted by an external source. It was discovered that these “hairy” BHs possess smaller shadows than the corresponding Kerr BHs. Additionally, under some conditions novel exotic shadow shapes can arise. Thus, hairy BHs could potentially provide new shadow templates for the afore mentioned experiments. These hairy BH solutions are also continuously connected to Boson Stars, described by the massive KleinGordon equation in curved spacetime. Thus, the gravitational lensing of the later is of especial interest to understand the new shadow shapes of the hairy BHs.
