Revisiting the shadow of braneworld black holes

TL;DR

This paper analyzes the shadows of rotating braneworld black holes using both near and far region metrics, revealing a critical angle that determines shadow shape and applying findings to M87* data to constrain black hole parameters.

Contribution

It introduces a novel method considering both near and far region metrics for black hole shadow analysis, providing new constraints on braneworld black hole parameters.

Findings

Identified a critical angle $ heta_c$ affecting shadow shape.

Determined how parameters influence shadow curves.

Applied analysis to M87* data to constrain black hole models.

Abstract

We revisit the shadows of rotating braneworld black holes in the Randall-Sundrum type II model, by considering not only the metric in the near region of the black hole but also the linearized metric in the far region where the observer stays. Our study is significantly different from previous studies, which relies only on the metric in the near region. From the study, we identify a critical angle $\theta_c$ which decides the shadow curve is open or closed: the shadow curve would be open if the observational angle $\theta_c<\theta_o\le\pi/2$, and the curve becomes closed when $0<\theta_o\le\theta_c$. We study how various parameters affect the shape of the shadow curve. We furthermore apply our analysis to the data of M87* from the Event Horizon Telescope and obtain a new constraint on the parameters of the braneworld black holes.