A Study of Black Holes in F(R)-ModMax Gravity: Shadow and Gravitational Lensing

The study of astrophysical phenomena like black hole shadows is an effective approach to properly understand the modified gravity and explore its validity. Motivated by recent astrophysical observations, we consider a black hole (BH) in F(R)-ModMax gravity and study the optical features such as the shadow geometrical shape, energy emission rate, and deflection of light. More specifically, we show how the variation of the parameters of the model imprints specific signatures on these optical quantities. In the following, we consider such black holes as supermassive BH and evaluate the parameters of the model with shadow size estimates done by the observations of M87* from the Event Horizon Telescope (EHT). According to our findings, no results consistent with EHT data are observed for AdS black holes in $F(R)$-ModMax gravity, while in the case of dS black holes, the resulting shadow is consistent with M87* shadow in a limited region of parameters.