Effects of Homogeneous Plasma on Strong Gravitational Lensing of Kerr Black Holes
Chang-Qing Liu1**, Chi-Kun Ding1, Ji-Liang Jing2
1Department of Physics, Hunan University of Humanities Science and Technology, Loudi 417000 2Department of Physics, and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha 410081
Abstract：Considering the Kerr black hole surrounded by a homogeneous unmagnetized plasma medium, we study the strong gravitational lensing on the equatorial plane of the Kerr black hole. It is found that the presence of the uniform plasma can increase the photon-sphere radius $r_{\rm ps}$, the coefficients $\bar{a}$ and $\bar{b}$, the angular position of the relativistic images ($\theta_{\infty}$), the deflection angle $\alpha(\theta)$ and the angular separation $s$. However, the relative magnitude $r_{\rm m}$ decreases in the presence of the uniform plasma medium. It is also shown that the impact of the uniform plasma on the effect of strong gravitational lensing becomes smaller as the spin of the Kerr black hole increases in the prograde orbit ($a>0$). In particular, for the extreme black hole ($a=0.5$), the effect of strong gravitational lensing in the homogeneous plasma medium is the same as the case in vacuum for the prograde orbit.
2017, Vol. 34 
