Kerr black hole shadows cast by extraordinary light rays with Weyl corrections

TL;DR

This paper studies how Weyl corrections influence photon trajectories and black hole shadows in Kerr spacetime, revealing birefringence effects and shape distortions that could inform electrodynamics theories.

Contribution

It introduces the analysis of Weyl correction effects on photon motion and black hole shadows in Kerr spacetime, highlighting birefringence and shadow shape modifications.

Findings

Weyl corrections cause birefringence in photon propagation.

Extraordinary rays lead to distorted black hole shadows.

Weyl corrections slightly stretch or squeeze the shadow vertically.

Abstract

We investigate the equation of motion for photons with Weyl corrections in a Kerr black hole spacetime in a small coupling case. Our results show that Weyl corrections yield phenomena of birefringence. The light rays propagating in the spacetime are separated into the ordinary rays and the extraordinary rays, and the propagation of the latter depends on the corrections. We probe the effects of Weyl corrections on the Kerr black hole shadows casted by the extraordinary rays and find that such corrections result in a weak stretching or squeezing in the vertical direction for the black hole shadows. Finally, we also study the change of the length of the Near-Horizon Extremal Kerr line (NHEK line) with Weyl corrections. These features could help us to understand the electrodynamics with Weyl corrections from black hole shadows.