Shadow of F(R)-EH Black Hole and Constraints from EHT Observations

TL;DR

This paper studies the optical properties and shadows of charged black holes in f(R) gravity coupled with nonlinear electrodynamics, constraining models using EHT observations and analyzing effects on black hole evaporation.

Contribution

It provides a detailed analysis of black hole shadows in f(R) gravity with nonlinear electrodynamics and constrains model parameters using EHT data.

Findings

Viable black hole shadow regions depend on charge and f(R) parameters.

De Sitter solutions are compatible with EHT observations, anti-de Sitter are not.

Electric charge increases evaporation rate, nonlinear effects and f(R) parameters suppress it.

Abstract

This work investigates the optical properties of a static, spherically symmetric, electrically charged black hole in f(R) gravity coupled to Euler-Heisenberg(EH) nonlinear electrodynamics(NLED). By analyzing photon trajectories in this background spacetime, we show how the model parameters affect light propagation, leading to wider ranges of lensed trajectories and photon rings. We identify regions of parameter space that admit physically consistent black hole shadows, characterized by the existence of a photon sphere located outside the event horizon and a shadow formed beyond it. These viable regions expand with increasing electric charge and increasing fR0, illustrating the interplay between gravitational and electromagnetic effects. By constraining the model using Event Horizon Telescope observations of M87*, we find that de Sitter black hole solutions remain compatible with the observational data, whereas anti-de Sitter solutions are disfavored for low electric charge and fR0 > -1. Finally, an analysis of the energy emission rate shows that higher electric charge enhances black hole evaporation, while stronger nonlinear electrodynamics effects and larger values of fR0 suppress it.