Shadow of charged black holes in Gauss-Bonnet gravity

TL;DR

This paper examines how Gauss-Bonnet gravity's higher curvature corrections influence the shadow of charged black holes in different spacetimes, revealing how the Gauss-Bonnet parameter alters shadow size and energy emission.

Contribution

It provides a detailed analysis of the impact of Gauss-Bonnet parameter on black hole shadows in both AdS and flat spacetimes, including effects of plasma and energy emission rates.

Findings

Gauss-Bonnet parameter increases shadow radius in AdS spacetime.

Gauss-Bonnet parameter decreases shadow radius in asymptotically flat spacetime.

Plasma medium modifies the black hole shadow silhouette.

Abstract

In this paper, we investigate the effect of higher curvature corrections from Gauss-Bonnet gravity on the shadow of charged black holes in both $AdS$ and Minkowski spacetimes. The null geodesic equations are computed in $d=5$ spacetime dimensions by using the directions of symmetries and Hamilton-Jacobi equation. With the null geodesics in hand, we then proceed to evaluate the celestial coordinates ($\alpha, \beta$) and the radius $R_s$ of the black hole shadow and represent it graphically. The effects of charge $Q$ of the black hole and the Gauss-Bonnet parameter $\gamma$ on the radius of the shadow $R_s$ is studied in detail. It is observed that the Gauss-Bonnet parameter $\gamma$ affects the radius of the black hole shadow $R_s$ differently for the $AdS$ black hole spacetime in comparison to the black hole spacetime which is asymptotically flat. In particular the radius of the black hole shadow increases with increase in the Gauss-Bonnet parameter in case of the $AdS$ black hole spacetime and decreases in case of the asymptotically flat black hole spacetime. We then introduce a plasma background in order to observe the change in the silhouette of the black hole shadow due to a change in the refractive index of the plasma medium. Finally, we study the effect of the Gauss-Bonnet parameter $\gamma$ on the energy emission rate of the black hole which depends on the black hole shadow radius and represent the results graphically.