Gravitational weak lensing by a naked singularity in plasma

Janis-Newman-Winicour (JNW) metric is the most general static spherically symmetric solution to the Einstein massless scalar equations with additional parameter v, encompassing the Schwarzschild metric as a particular case when nu = 1. It admits globally naked strong curvature singularity. We investigate weak-field lensing by JNW spacetime naked singularities when surrounded by plasma for three distributions: uniform, singular isothermal spheres and non-singular isothermal gas spheres. In the plasma's presence, we find that the gravitational deflection differs from the vacuum deflection angle. The gravitational deflection angle in plasma depends on the frequency of a photon. In addition, the lens equation obtained the observed quantity of the Einstein angle and magnification of the image's brightness for various specific parameters v analytically and found that these expressions are modified compared to the lensing quantities for standard Schwarzschild black holes, which are regained as a particular case when nu = 0. We also discuss the influence of plasma on lensed images formed by photons. We find the deflection angle increases with JNW parameter v and plasma frequency in all the three cases, but the increase is sharp with nu only. Interestingly, for a given v and plasma frequency, the deflection angle decreases with the impact parameter b