Observable characteristics of the charged black hole surrounded by thin disk accretion in Rastall gravity

TL;DR

This study explores the observable features of charged black holes with thin disk accretion in Rastall gravity, highlighting how radiation parameters and disk position influence the black hole's imaging and flux contributions.

Contribution

It provides new insights into how Rastall gravity affects black hole imaging and the relative importance of different emission regions in observed signals.

Findings

Radiation field parameter significantly affects emission and ring radii.

Direct emission dominates the observed flux, while lensing and photon rings are minor.

Lensing and photon rings are not observable with current EHT resolution.

Abstract

The observable characteristics of the charged black hole (BH) surrounded by a thin disk accretion are investigated in the Rastall gravity. We found that the radii of the direct emission, lensing ring, and photon ring dramatically increased as the radiation field parameter increases, but they only weakly depend on the BH charge. Three positions of the radiation accretion disk relative to the BH are considered, i.e., the innermost accretion disk is closed to the radii of the innermost stable circular orbit, the photon ring of the BH, and the event horizon of the BH. The observed images in three cases respectively are obtained. It is found that the total observed flux is dominated by the direct emission, the lensing ring provides a small contribution, and the photon ring is negligible. The lensing and photon rings could not be observed in the blurred image with the EHT resolution. Our results suggest that the observable characteristics of the charged BH surrounded by the thin disk accretion in the Rastall gravity depend on both the BH space-time structure and the position of the radiating accretion disk with respect to the BH. The research of these BH images may serve as a probe for the BH-disk structure in M87$^{*}$ like nearby active galactic nuclei.