Strong Gravitational Lensing and Shadow Signatures of Anisotropic Black Holes in Plasma

Abstract We study strong gravitational lensing and black hole shadow in a static, spherically symmetric spacetime sourced by anisotropic matter with exponentially decaying hair, in the presence of a non-magnetized plasma. The geometry is characterized by deformation parameters $\tilde{v}_2$ and $\tilde{v}_c$, which influence the photon sphere and shadow in opposing ways: $\tilde{v}_2$ shrinks both while $\tilde{v}_c$ enlarges them. Plasma effects systematically increase the shadow size and suppress the deflection angle. Using EHT observations of Sgr A*, we constrain the parameter space of the model. Our analysis demonstrates that anisotropic matter hair and plasma environments produce distinguishable signatures in strong-field gravitational optics, offering potential probes for testing deviations from the standard gravity.

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