Gravitational lensing and shadow of charged black holes in the low-energy limit of string theory

TL;DR

This paper studies how the dilaton parameter affects the shadow size and energy emission rate of charged black holes in string theory, providing numerical estimates for gravitational lensing observables in the strong field regime.

Contribution

It introduces a new class of black hole solutions in dilaton gravity and analyzes the impact of the dilaton parameter on shadow size and lensing features.

Findings

Shadow size increases with the dilaton parameter N.

Energy emission rate increases as N increases.

Numerical estimates for gravitational lensing observables are provided.

Abstract

In this work, we investigate the shadow cast and strong field gravitational lensing of a new class of black hole solutions in dilaton gravity where dilaton field is coupled with nonlinear Maxwell invariant [Younesizadeh et al. in Int J Mod Phys A 34(35):1950239]. The space-time is a stationary axisymmetric geometry. The key part in our investigations is finding the effect of dilaton parameter N on the size of shadows and the energy emission rate. As the N parameter increases, the size of black hole shadow increases. Also, the energy emission rate increases with increase in the dilaton parameter N. By supposing the gravitational field of the supermassive object at the heart of Milky Way galaxy described by this metric, we estimated the numerical values of the observables for gravitational lensing in the strong field limit.