Shadows and Strong Gravitational Lensing by Van der Waals Black Hole in Homogeneous Plasma

Abstract

In this paper, we first analyze the horizon structure of the Van der Waals(VdW) black hole and then investigate its shadow in the absence of a plasma medium as well as the presence of a homogeneous plasma medium. We find that both the Van der Waals parameters $a$ and $b$ have a significant effect on the shadow of the black hole. We also observe that the radius of the shadow in a homogeneous plasma medium decreases while parameter $σ=\frac{ω_p}{ω_{\infty}}$ ( the ratio of plasma frequency and photon frequency) increases and the radius of the shadow inhomogeneous plasma medium is larger than the vacuum medium. We also discuss the strong gravitational lensing in a homogeneous plasma medium. We observe that the photon sphere radius, deflection limit coefficients and deflection angle in the strong field are highly affected by the presence of a homogeneous plasma medium. We also find that the deflection angle in the strong field limit by the Van der Waals black hole with the homogeneous plasma is greater than that of the Vacuum medium. Further, we discuss the observables quantities angular position $θ_{\infty}$, separation $S$ and magnification $r_{mag}$ by taking the example of a supermassive black hole in the strong field limit with the effects of homogeneous plasma. It is concluded that the Van der Waals parameters $a$, $b$ and homogeneous plasma medium have a significant effect on both the shadows and strong gravitational lensing.