Determining properties of a rotating black hole from its shadow (presentación oral, coautor)

JAVIER BADÍA; ERNESTO F. EIROA

Córdoba

Conferencia; Grav19; 2019

FAMAF, Universidad de Córdoba, Argentina

Massive objects deflect the trajectories of light rays in their vicinity, as a consequence of the space-time curvature. If the object is a black hole, this creates an optical effect in which part of the trajectories of photons coming from the region behind it are trapped, forming a dark zone called the shadow. For a static black hole the shadow has a circular shape, but for a rotating one it is deformed in an asymmetric manner, depending on the angle of observation and the spin of the black hole. We review the usual method for analytically obtaining the contour of the shadow of a black hole via the Hamilton-Jacobi equation, together with its application to the Kerr solution of General Relativity and other solutions of interest taken from alternative theories. We also discuss recent developments proposing that black hole properties can be extracted from the observation of the shadow, allowing for a determination of physical quantities and parametrizing possible deviations from the Kerr solution. We briefly discuss observational aspects regarding the supermassive black hole located at the galactic center.