Gravitational lensing by a non-Schwarzschild black hole in a plasma

We study gravitational lensing in the vicinity of a massive object described by non-Schwarzschild geometry surrounded by a homogeneous plasma. The expression for the deflection angle in a non-Schwarzschild space-time in the weak field regime in the presence of plasma have been derived. It has been shown that the obtained deflection angle depends on (i) the frequency of the electromagnetic wave, due to the dispersion properties of the plasma; (ii) the gravitational mass M; and (iii) deformation parameter epsilon of the gravitational lens. Moreover, the influence of deformation parameter of the gravitational lens and plasma frequency on the magnification of brightness of the source star has been studied in the case of microlensing.