Strong field limit analysis of gravitational lensing in Kerr-Taub-NUT spacetime

In this paper, we investigate the strong gravitational lensing by the\nstationary, axially-symmetric black hole in Kerr-Taub-NUT spacetime in the\nstrong field limit. The deflection angle of light ray and other strong\ndeflection limit coefficients are obtained numerically and they are found to be\nclosely dependent on the NUT charge $n$ and spin $a$. The magnification and the\npositions of the relativistic images are computed. The caustics are studied and\nthe results show that these caustics drift away from the optical axis, which is\nquite different from the Schwarzschild black hole case. Moreover, the\nintersections of the critical curves on the equatorial plane are obtained and\nit is shown that they increase with the NUT charge. These results show that\nthere is a significant effect of the NUT charge on the strong gravitational\nlensing.\n

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