Equatorial light bending around a Hairy Kiselev black hole

Abstract

We investigate the deflection angle of light rays confined to the equatorial plane of a Hairy Kiselev black hole. The analysis includes a thorough study of the horizon structure and critical parameters, leading to an analytic expression for the deflection angle in terms of elliptic integrals. Our results confirm that the deflection angle decreases with increasing impact parameter, in agreement with classical predictions of gravitational lensing. The influence of the scalar field, characterized by the coupling constant, shows a nontrivial effect: while moderate values of the coupling constant initially enhance light bending, further increases lead to a suppression of the deflection in the strong-field regime due to modifications in spacetime geometry. Comparative analysis among the Schwarzschild, Kiselev, and Hairy Kiselev black holes indicates that the presence of a quintessence-like field tends to enhance the deflection, whereas the scalar hair component reduces it. Further, we investigate the angular shadow radius of the Hairy Kiselev black hole for a static observer and analyze how mass-dependent variations affect the shadow features. These findings underscore the significant role of scalar fields and exotic matter distributions in shaping light propagation in a modified gravity scenario.