Frequency shifts of photons emitted from geodesics of nonlinear electromagnetic black holes

Abstract

We analyzed the frequency shifts of photons emitted from massive particles that move in stable geodesics around black holes with nonlinear electrodynamics. The motion of the photon is modified by an effective metric when the Einstein gravity is coupled with nonlinear electrodynamics. The kinematic shifts for photons are modified by the magnetic and electric factors that make the difference between the linear and nonlinear electrodynamics. As an illustration, we present the frequency shifts of the photons for black holes with nonlinear electrodynamics, two magnetic black holes, and two electric black holes, the Bardeen and Bronnikov black holes for the magnetic charge and the Born–Infeld and Dymnikova black holes for electric charge. These frequency shifts are compared with their linear electromagnetic counterpart.