Do shadows of Sgr A* and M87* indicate black holes with a magnetic monopole charge?

TL;DR

This paper investigates whether the shadows of Sgr A* and M87* can be explained by Bardeen black holes, which are regular black holes with magnetic monopole charge, using recent EHT observations.

Contribution

It compares Bardeen black hole shadow predictions with observed images, suggesting Sgr A* may be better explained by a regular black hole model.

Findings

M87* shadow favors Kerr black hole model

Sgr A* shadow can be better explained by Bardeen black hole

Regular black holes may be relevant in astrophysical observations

Abstract

We study the prospect of Bardeen black holes in explaining the observed shadow of Sgr A* and M87*. Bardeen black holes are regular black holes endowed with a magnetic monopole charge that arise in Einstein gravity coupled to non-linear electrodynamics. These black holes are interesting as they can evade the r = 0 curvature singularity arising in general relativity. It is therefore worthwhile to look for signatures of Bardeen black holes in astrophysical observations. With two successive release of black hole images by the Event Horizon Telescope (EHT) collaboration, the scope to test the nature of strong gravity has substantially increased. We compare the theoretically computed shadow observables with the observed image of Sgr A* and M87*. Our analysis reveals that while the observed angular diameter of M87* favors the Kerr scenario, the shadow of Sgr A* can be better explained by the Bardeen background. This indicates that although rare, certain black holes exhibit a preference towards regular black holes like the Bardeen spacetime.