Kerr black hole shadow: non-parametric description and analytic methods of spin extraction

摘要

In this paper we study the asymmetry of the shadow cast by a rotating Kerr black hole. Using Bardeen parametric formulas we plot contours of black hole shadows for different values of black hole's angular momentum and different observer's positions. In the case of the equatorial observer we present an equation that explains the behaviour of the numeric Hioki-Maeda curve, which is used to measure the black hole angular momentum from it's shadow. Also in this case we introduce a new observable of the shadow and derive a simple formula that allows to constrain the black hole spin via measuring this observable. Finally we come out with the formula that provides the non-parametric description of the black hole shadow.