Polarization distribution in the image of a synchrotron emitting ring around a regular black hole

Abstract

The polarized images of a synchrotron emitting ring are studied in the regular Hayward and Bardeen black hole spacetimes. These regular black holes carry a magnetic field in terms of gravity coupled to nonlinear electrodynamics. Results show that the main features of the polarization images of the emitting rings are similar in these two regular black hole spacetimes. As the magnetic charge parameter increase, the polarization intensity and the electric vector position angle in the image plane increase in Hayward and Bardeen black hole spacetimes. Moreover, the polarization intensity and electric vector position angle in the image of the emitting ring in the Hayward black hole spacetime are closer to those in the Schwarzschild case. The effects of the magnetic charge parameter on the Strokes $Q-U$ loops are also slightly smaller in the Hayward black hole spacetime. This information stored in the polarization images around Hayward and Bardeen black holes could help understand regular black holes and the gravity coupled to nonlinear electrodynamics.