Black hole shadows in accretion disks and spin parameters of black holes: Massive black holes and stellar mass black holes

Abstract

Can we determine spin parameters of black holes by observations of black hole shadows in accretion disks? In order to answer this question, we have investigated shapes and positions of black hole shadows in optically thick accretion disks around Kerr black holes. In conclusion, in order to measure black hole spin parameters from shapes and positions of black hole shadows, it is crucially important to determine a position of a mass centers of a black hole in a region of a black hole shadow.