Testing Rotating Regular Metrics as Candidates for Astrophysical Black Holes

Understand

The Event Horizon Telescope, a global submillimeter wavelength very long baseline interferometry array, produced the first image of supermassive black hole M87* showing a ring of diameter $\theta_d= 42\pm 3\,\mu$as, inferred a black hole mass of $M=(6.5 \pm 0.7) \times 10^9 M_\odot $ and allowed us to investigate the nature of strong-field gravity.

• The observed image is consistent with the shadow of a Kerr black hole, which according to the Kerr hypothesis describes the background spacetimes of all astrophysical black holes.
• The hypothesis, a strong-field prediction of general relativity, may be violated in the modified theories of gravity that admit non-Kerr black holes.
• Here, we use the black hole shadow to investigate the constraints when rotating regular black holes (non-Kerr) can be considered as astrophysical black hole candidates, paying attention to three leading regular black hole models with additional parameters $g$ related to nonlinear electrodynamics charge.