Shadows of Bonnor black dihole by chaotic lensing

TL;DR

This paper numerically investigates the shadows of Bonnor black diholes, revealing how magnetic dipole strength influences shadow shape and fractal structures, with unique connectivity features compared to similar binary black hole systems.

Contribution

It introduces a detailed numerical analysis of Bonnor black dihole shadows, highlighting the effects of magnetic dipole parameters on shadow morphology and connectivity, which differ from known binary black hole shadows.

Findings

Shadow shape transitions from black disk to concave with eyebrows

Fractal and self-similar structures in shadow boundaries

Connected shadows and eyebrows for Bonnor dihole, unlike in Majumdar-Papapetrou systems

Abstract

We have studied numerically the shadows of Bonnor black dihole through the technique of backward ray-tracing. The presence of magnetic dipole yields non-integrable photon motion, which affects sharply the shadow of the compact object. Our results show that there exists a critical value for the shadow. As the magnetic dipole parameter is less than the critical value, the shadow is a black disk, but as the magnetic dipole parameter is larger than the critical one, the shadow becomes a concave disk with eyebrows possessing a self-similar fractal structure. These behavior are very similar to those of the equal-mass and non-spinning Majumdar-Papapetrou binary black holes. However, we find that the two larger shadows and the smaller eyebrow-like shadows are joined together by the middle black zone for the Bonnor black dihole, which is different from that in the Majumdar-Papapetrou binary black holes spacetime where they are disconnected. With the increase of magnetic dipole parameter, the middle black zone connecting the main shadows and the eyebrow-like shadows becomes narrow. Our result show that the spacetime properties arising from the magnetic dipole yields the interesting patterns for the shadow casted by Bonnor black dihole.