Optical properties of black hole in the presence of plasma: shadow

TL;DR

This paper investigates how plasma affects the optical appearance and energy emission of black holes, showing that plasma alters shadow size and reduces energy emission, with detailed analysis for Kerr and Schwarzschild black holes.

Contribution

It provides a detailed analysis of plasma effects on black hole shadows and energy emission, including the specific case of Schwarzschild black holes and the influence of plasma parameters.

Findings

Plasma changes the shape and size of black hole shadows depending on parameters.

The photon sphere remains unchanged in Schwarzschild black holes with plasma.

Energy emission rate decreases in the presence of plasma.

Abstract

We have studied photon motion around axially symmetric rotating Kerr black hole in the presence of plasma with radial power-law density. It is shown that in the presence of plasma the observed shape and size of shadow changes depending on i) plasma parameters, ii) black hole spin and iii) inclination angle between observer plane and axis of rotation of black hole. In order to extract pure effect of plasma influence on black hole image the particular case of the Schwarzschild black hole has also been investigated and it has been shown that i) the photon sphere around the spherical symmetric black hole is left unchanged under the plasma influence, ii) however the Schwarzschild black hole shadow size in plasma is reduced due to the refraction of the electromagnetic radiation in plasma environment of black hole. The study of the energy emission from the black hole in plasma shows that in the presence of plasma the maximal energy emission rate from the black hole decreases.