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

TL;DR

This paper analyzes how the NUT charge and spin of a Kerr-Taub-NUT black hole influence strong gravitational lensing, revealing significant deviations from Schwarzschild black hole lensing behavior.

Contribution

It provides a detailed numerical study of strong gravitational lensing in Kerr-Taub-NUT spacetime, highlighting the effects of NUT charge and spin on lensing features.

Findings

Deflection angle depends on NUT charge and spin

Relativistic image positions and magnifications are computed

Caustics drift away from the optical axis with NUT charge

Abstract

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