Shadow analysis of an approximate rotating black hole solution with weakly coupled global monopole charge

TL;DR

This paper studies the shadow of a rotating black hole with a global monopole charge, revealing how this charge affects observable features and can be constrained by astronomical data.

Contribution

It introduces a novel analysis of black hole shadows considering global monopole charge using a modified Newman-Janis algorithm, linking theoretical models with observational constraints.

Findings

Global monopole charge constrained to $0 \\leq \\gamma \\lesssim 0.036$ from observations.

Weak coupling parameter constrained to $-0.2 \\lesssim \\alpha \\leq 0$.

Shadow features influenced by monopole charge and rotation, aiding in distinguishing black hole types.

Abstract

We investigate the shadow properties of a rotating black hole with a weakly coupled global monopole charge, using a modified Newman-Janis algorithm. This study explores how this charge and rotational effects shape the black hole's shadow, causal structure, and ergoregions, with implications for distinguishing it from Kerr-like solutions. Analysis of null geodesics reveals observable features that may constrain the global monopole charge and weak coupling parameters within nonminimal gravity frameworks. Observational data from M87* and Sgr A* constrain the global monopole charge and coupling constant to $0 \leq \gamma \lesssim 0.036$ and $-0.2 \lesssim \alpha \leq 0$, respectively.