相关论文: Constraining rotating black hole via curvature rad…
We consider applications of the curvature radius of a Kerr black hole shadow and propose three new approaches to simultaneously determine the black hole spin and inclination angle of the observer. The first one uses only two symmetric…
The motion of photons around the Kerr-Newman-dS black hole surrounded by quintessence and a cloud of strings is investigated. The existence of the Carter constant leads to that of unstable circular photon orbits on a two-dimensional plane…
Inspired by the observations of supermassive black hole M87* in \emph{Event Horizon Telescope }(EHT) experiment, a remarkable surge in black hole physics is to use the black hole shadow's observables to distinguish general relativity (GR)…
In this paper, the shadows cast by non-rotating and rotating modified gravity black holes are investigated. In addition to the black hole spin parameter $a$ and the inclination angle $\theta$ of observer, another parameter $\alpha$…
We examine the shadow cast by a Kerr black hole, focusing on constraints on photons corresponding to different shadow boundaries. The photons are related to different orbital ranges and impact parameter values, creating a map of the shadow…
The recent observation of the shadow of the supermassive compact object M87$^*$ by the Event Horizon Telescope (EHT) collaboration has opened up a new window to probe the strong gravity regime. In this paper, we study shadows cast by two…
In this paper, we study the influence of the parameters for the accelerating Kerr-Newman black hole on the shadows and the constraints, extensively. We find that the rotating parameter $a$, the charge parameter $e$, and the inclination…
When the the shadow image of a supermassive black hole in the center of M87 was obtained a new era in the observational astrophysics began. The resolution improvement would allow to test extended gravity models at event horizon scales. We…
Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87* shadow size to infer constraints on the physical charges…
From the viewpoint of differential geometry and topology, we investigate the characterization of the shadows in a Kerr spacetime. Two new quantities, the length of the shadow boundary and the local curvature radius are introduced. Each…
The Event Horizon Telescope (EHT) has guided strong-field gravitational physics by providing the first direct images of the supermassive black holes M87* and Sagittarius A*. The EHT observations offer unprecedented opportunities to test…
The M87* black hole shadow observation by the Event Horizon Telescope (EHT) has enabled us to test the modified gravity theories in the extreme-field regime and estimating the black hole parameters. Having this assertion, we investigate the…
The optical properties of rotating black holes in Kaluza-Klein theory described by the total mass, spin, and electric and magnetic charges are investigated in detail. Using a developed general relativistic ray-tracing code to calculate the…
We discuss the horizon properties, shadow cast, and the weak gravitational lensing of charged rotating regular black holes, which in addition to mass ($M$) and rotation parameter ($a$) have an electric charge ($Q$) and magnetic charge…
We succeed to find compact analytical expressions which allow to easily extract the black hole spin from observations of its shadow, without need to construct or model the entire curve of the shadow. The deformation of Kerr black hole…
It is believed that curvature singularities are a creation of general relativity and hence, in the absence of a quantum gravity, models of nonsingular black holes have received significant attention. We study the shadow (apparent shape), an…
We study the shadow of rotating charge black holes in the presence of quintessence. The shadow of a rotating black hole is a distorted circle and in our study, we find that the shape and size of the black hole shadow depend upon four…
Following up on a recent analysis by Psaltis et al. [Phys. Rev. Lett. 125, 141104 (2020)], we show that the observed shadow size of M87$^*$ can be used to unambiguously and robustly constrain the black hole geometry in the vicinity of the…
Observations of the black hole shadow of supermassive black holes, such as Sagittarius A* at the center of our Milky Way galaxy, allow us to study the properties of black holes and the nature of strong-field gravity. According to the Kerr…
The Event Horizon Telescope, a global submillimeter wavelength very long baseline interferometry array, produced the first image of supermassive black hole M87* showing a ring of diameter $\theta_d= 42\pm 3\,\mu$as, inferred a black hole…