NUT charges and black hole shadows

TL;DR

This paper explores how NUT charges influence the appearance of black hole shadows, revealing unique effects depending on observer position and singularity placement, including size and distortion variations.

Contribution

It provides new insights into the impact of NUT charges on black hole shadows, especially regarding observer-dependent shadow size and distortion effects.

Findings

Shadow size can be very small near string singularities.

Shadow distortion increases when approaching the singularity.

Maximal shadow size occurs at the north pole for certain NUT configurations.

Abstract

We study the nontrivial effects of the NUT charges on the shadows of the Kerr-Taub-NUT black holes seen by zero-angular-momentum-observers. Inclination angles with which the observers gain maximal, locally extreme or minimal shadow sizes and distortions are investigated for the black holes with different NUT charges and distributions of string singularities. Typically, we discover that when the observer approaches the string singularity, the shadow size can be relatively very small while the shadow distortion being relatively quite large. And exceptionally, we find that when the string singularity locates only at the south pole axis of the black hole with large enough NUT charge, the shadow size is maximal for a north pole observer.