Plasma impact on black hole shadow and gravitational weak lensing for Schwarzschild-like black hole

Abstract

This article delves into the observational properties of a Schwarzschild-like black hole (BH). Initially, the research provides a succinct examination of the spacetime geometry and the configuration of its horizon. Furthermore, we study the photon dynamics around the Schwarzschild-like BH in the presence of the plasma using the Hamiltonian formalism. It was found that the photon sphere radii increase under the influence of the plasma frequency and vice versa for the spacetime parameters. Further exploration is dedicated to understanding how the plasma affects the shadow of the BH, and we find that the radius of the BH shadow shrinks with the rise of the $ξ$ parameter and plasma frequency. We then turn to the getting constraint of the spacetime parameters and the plasma frequency by using the observational data released by the Event Horizon Telescope (EHT) collaboration for the M87* and Sgr A*. Additionally, the research scrutinises the phenomenon of gravitational weak lensing in the vicinity of a Schwarzschild-like BH, considering both uniform and non-uniform plasma scenarios. The outcomes demonstrate that the angle of deflection increases under the influence of a uniform plasma frequency, whereas the opposite is true for non-uniform plasma. In both scenarios, a rise in the spacetime parameters results in a decrease in the deflection angle. Finally, we investigate the magnification of the gravitationally lensed image. The effect of the spacetime parameters and plasma frequencies on the total magnification are same as in the deflection angles.

Figures (12)

• Figure 1: The plot shows the radial dependence of the metric function for the different values of the $\xi$ parameter (left panel) and $\gamma$ parameter (right panel). Here, we set $\gamma=0.5$ and $\xi=0.5$ for the left and right panels, respectively.
• Figure 2: The plot illustrates the dependence of the event horizon radii of the Schwarzschild-like BH on the spacetime parameters.
• Figure 3: The plot demonstrates the photon sphere radii as a function of the plasma frequency for the different values of the $\xi$ (left panel) and $\gamma$ (right panel) parameters. Here, we set $\gamma=0.5$ and $\xi=0.5$ for the left and right panels, respectively.
• Figure 4: The plot shows the dependence of the BH shadow radii on the plasma frequency for the different values of the $\xi$ (left panel) and $\gamma$ (right panel) parameters. Here, we set $\gamma=0.5$ and $\xi=0.5$ for the left and right panels, respectively.
• Figure 5: The plot illustrates the profile of the shadow cast by the Schwarzschild-like BH for the different values of the $\xi$ parameter and the plasma frequency.