Related papers: Determining parameters of a spherical black hole w…
We propose a new method to determine the physical parameters of Kerr black holes (namely, specific angular momentum $a$, inclination angle $i$, and distance $D$ from an observer) only from the shadow's information such as the size and…
Can we determine a spin parameter of a black hole by observation of a black hole shadow in an accretion disk? In order to answer this question, we make a qualitative analysis and a quantitative analysis of a shape and a position of a black…
We explore a simple spherical model of optically thin accretion on a Schwarzschild black hole, and study the properties of the image as seen by a distant observer. We show that a dark circular region in the center --- a shadow --- is always…
We consider a simple spherical model consisting of a Schwarzschild black hole of mass $M$ and a dark matter of mass $\Delta M$ around it. The general formula for the radius of black-hole shadow has been derived in this case. It is shown…
In this study, we focus on a static spherically symmetric $f(R)$ black hole spacetime characterized by a linear dark matter-related parameter. Our investigation delves into understanding the influence of different assumed values of this…
In this work, we study some characteristics and gravitational signatures of the Schwarzschild black hole immersed in a Hernquist dark matter halo (SBH-HDM). We determine the black hole's remnant radius and mass, which provide useful…
We present a method for determining the physical parameters of a Kerr-Newman black hole through shadow observation. In a system comprising a Kerr-Newman black hole, an observer, and a light source, the relevant parameters are mass $M$,…
The accretion around the black hole plays a pivotal role in the theoretical analysis of black hole shadow, and of the black hole observation in particular. In this paper, we mainly study the shadow and observation characteristics of…
We investigate the observable signatures -- the shadow, the throat silhouette, and the image of a thin accretion disk -- for a family of static, spherically symmetric wormholes with an arbitrary throat profile. First, we derive expressions…
This study investigates the accretion process and observational signatures of thin accretion disks around a Schwarzschild black hole (BH) embedded in a Dehnen-type dark matter (DM) halo. We examine the influence of the density {\rho}_{s}…
The Schwarzschild black hole in the Cold Dark Matter (CDM) halo is studied, and the radiation laws of the thin accretion disk near the black hole are discussed and summarized. The orbits of light around the black hole are also calculated.…
We investigate the luminosity of the accretion disk for a static black hole surrounded by dark matter with anisotropic pressure. We calculate all basic orbital parameters of test particles in the accretion disk, such as angular velocity,…
Rotating regular black hole, as a promising extension beyond general relativity, offer a phenomenological model that resolves spacetime singularities. In this study, we investigate the observational features of thin accretion disk around a…
We study the optical appearance of a de Sitter-Schwarzschild black hole and its distinguishability from a Schwarzschild black hole. By exploring various accretion models and emission profiles, we investigate the impact of different…
We present the shape of the black hole shadow on the standard background screen as it is registered by the distant observer. The screen is an infinite plane, emitting the quanta uniformly distributed to a hemisphere. The source of emission…
First sketch of black hole from M87 galaxy was obtained by Event Horizon Telescope, recently. As appearance of black hole shadow reflects space-time geometry of black holes, observations of black hole shadow may be a promising way to test…
A black hole casts a shadow as an optical appearance because of its strong gravitational field. We study how to determine the spin parameter and the inclination angle by observing the apparent shape of the shadow, which is distorted mainly…
This paper investigates the optical appearance of a Schwarzschild-like black hole (BH) surrounded by a Dehnen-(1, 4, 5/2) type dark matter (DM) halo, with a focus on how the DM halo's density $\rho_{s}$ and radius $r_{s}$ influence the BH's…
The inner shadow of a black hole, as a projection of the event horizon, is regarded as a potential tool for testing gravitational theories and constraining system parameters. Whether this holds in the case of a tilted accretion disk…
A hairy Schwarzschild black hole describes the deformation of Schwarzschild black hole due to including additional sources. It is found that depending on the hairy parameters, the photons' configurations around this black hole can be…