Shadow Images of Ghosh-Kumar Rotating Black Hole Illuminated By Spherical Light Sources and Thin Accretion Disks

TL;DR

This paper explores how the shadow images of Ghosh-Kumar rotating black holes are affected by spacetime parameters, celestial light sources, and accretion disks, revealing shape transformations and flux variations.

Contribution

It provides a detailed analysis of shadow image deformations and flux changes due to parameter variations, using backward ray-tracing in the Ghosh-Kumar black hole spacetime.

Findings

Shadow shapes transition from circles to ovals with increasing parameters.

Einstein rings deform into arcs as spacetime parameters change.

Redshift and blueshift effects are influenced by observational angles and parameters.

Abstract

This study investigates the astronomical implications of the Ghosh-Kumar rotating Black Hole (BH), particularly its behaviour on shadow images, illuminated by celestial light sources and equatorial thin accretion disks. Our research delineates a crucial correlation between dynamics of the shadow images and the parameters $a$,~ $q$ and the $\theta_{obs}$, which aptly reflect the influence of the model parameters on the optical features of shadow images. Initially, elevated behavior of both $a$ and $q$ transforms the geometry of the shadow images from perfect circles to an oval shape and converges them towards the centre of the screen. By imposing the backward ray-tracing method, we demonstrate the optical appearance of shadow images of the considering BH spacetime in the celestial light source. The results demonstrate that the Einstein ring shows a transition from an axisymmetric closed circle to an arc-like shape on the screen as well as producing the deformation on the shadow shape with the modifications of spacetime parameters at the fixed observational position. Next, we observe that the attributes of accretion disks along with the relevant parameters on the shadow images are illuminated by both prograde and retrograde accreting flow. Our study reveals the process by which the accretion disk transitions from a disk-like structure to a hat-like shape with the aid of observational angles. Moreover, with an increase of $q$, the observed flux of both direct and lensed images of the accretion disk gradually moves towards the lower zone of the screen. Furthermore, we present the intensity distribution of the redshift factors on the screen. Our analysis suggests that the observer can see both redshift and blueshift factors on the screen at higher observational angles, while augmenting the values of both $a$ and $q$, enhancing the effect of redshift on the screen.