Exploring potential astrophysical applications of black holes in nonlinear electrodynamics

TL;DR

This paper investigates the properties of regular black holes in nonlinear electrodynamics, focusing on photon motion, shadows, and redshift, and compares them to Reissner-Nordström black holes to explore potential astrophysical applications.

Contribution

It introduces and analyzes fully regular, electrically charged black hole solutions in NED, examining their observational signatures and constraints from astrophysical data.

Findings

For low charge-to-mass ratios, RBHs resemble RN black holes.

Higher charge-to-mass ratios lead to observable differences from RN black holes.

Constraints on charge-to-mass ratios are derived from Sagittarius A* and M87* data.

Abstract

Spacetimes arising from nonlinear electrodynamics (NED) are a good laboratory for studying both the nature of regular black holes (RBH) solutions and the imprints of nonlinear electromagnetic fields within this context. Over the past few decades, NED-sourced black hole (BH) spacetimes have attracted considerable attention, but electrically charged RBHs obtained in the so-called $F$ framework have been less addressed in the literature. We consider two members of the h-family of electrically charged, fully RBHs that are solutions to general relativity minimally coupled to NED. Because of their potential astrophysical and astronomical applications, we mainly focus our investigation on the motion of photons and its implications in the shadow radius and gravitational and kinematic redshift, considering the effective geometry followed by photons in NED. For a BH charge-to-mass ratio below some moderate value, there is almost no way to distinguish these members (and likely all members) of the h-family from the Reissner-Nordstr\"om (RN) BH. In its turn, for a BH charge-to-mass ratio above some moderate value, we observe discrepancies in their physical and geometric properties in comparison to those of the RN BH. Furthermore, we also consider observational data for Sagittarius A$^{*}$ and Messier 87$^{*}$ BHs to impose some constraints on the charge-to-mass ratio of the fully RBHs.