Kerr black hole surrounded by a cloud of strings and its weak gravitational lensing in Rastall gravity

Abstract

In this paper, an exact solution of Kerr black hole surrounded by a cloud of strings in Rastall gravity is obtained by Newman-Janis algorithm without complexification, and the influence of the string parameter $a_0$ on the black hole thermodynamics is studied. Furthermore, according to this black hole solution, we investigate the effect of a cloud of strings on gravitational deflection of massive particles. For a receiver and a source at infinite distance from the lens object, we use an osculating Riemannian manifold method. While the distance is finite, we apply the generalized Jacobi metric method. For the case between the two situations, the Jacobi-Maupertuis Randers-Finsler metric and Gauss-Bonnet theorem are employed. We find that the string parameter $a_0$ has obviously modification on the gravitational deflection of massive particles. Our result is reduced to the deflection angle of light by Kerr black hole surrounded by a cloud of strings in general relativity.