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Quantum effects in general induce scale dependence in the coupling constants. We explore this possibility in gravity, with a scale-dependent Newton coupling. When applied to Kerr black holes with such a running coupling, the consistency of…

General Relativity and Quantum Cosmology · Physics 2026-02-19 Che-Yu Chen , Chiang-Mei Chen , Nobuyoshi Ohta

According to the no-hair theorem, all astrophysical black holes are fully described by their masses and spins. This theorem can be tested observationally by measuring (at least) three different multipole moments of the spacetimes of black…

High Energy Astrophysical Phenomena · Physics 2015-05-18 Tim Johannsen , Dimitrios Psaltis

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…

High Energy Astrophysical Phenomena · Physics 2009-08-05 Kenta Hioki , Kei-ichi Maeda

We study the shadows of the fully non-linear, asymptotically flat Einstein-dilaton-Gauss-Bonnet (EdGB) black holes (BHs), for both static and rotating solutions. We find that, in all cases, these shadows are smaller than for comparable Kerr…

General Relativity and Quantum Cosmology · Physics 2017-03-22 Pedro V. P. Cunha , Carlos A. R. Herdeiro , Burkhard Kleihaus , Jutta Kunz , Eugen Radu

We analyze the shadow of charged stationary axially symmetric space-time (Kerr-Sen dilaton-axion black hole). This black hole is defined by a mass $M$, a spin $a$ and $r_{\alpha}=Q^{2}/M$, where $Q$ is the electric charge. Shadows are…

General Relativity and Quantum Cosmology · Physics 2016-11-01 Sara Dastan , Reza Saffari , Saheb Soroushfar

Black hole shadows and photon spheres offer valuable tools for investigating black hole properties. Recent observations by the Event Horizon Telescope Collaboration have confirmed the existence of rotating black holes. Black hole parameters…

General Relativity and Quantum Cosmology · Physics 2024-11-26 Vitalii Vertogradov , Ali Övgün , Reggie C. Pantig

Within 5-10 years, very-long baseline interferometry (VLBI) facilities will be able to directly image the accretion flow around SgrA$^*$, the super-massive black hole candidate at the center of the Galaxy, and observe the black hole…

General Relativity and Quantum Cosmology · Physics 2014-06-19 Naoki Tsukamoto , Zilong Li , Cosimo Bambi

The black hole shadow, a direct probe of the event horizon's gravitational influence, has been observationally confirmed by the Event Horizon Telescope (EHT). While theoretical models of shadows in vacuum are mature, real astrophysical…

High Energy Astrophysical Phenomena · Physics 2025-11-20 Sai Karan Mukthapuram , Sandeep Kumar Kataria

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…

General Relativity and Quantum Cosmology · Physics 2024-03-26 Yuan Meng , Xiao-Mei Kuang , Xi-Jing Wang , Bin Wang , Jian-Pin Wu

We study the shadows cast by near-extremal Kerr-MOG black holes for different values of the parameter in modified gravity (MOG). In particular, we consider an isotropic emitter orbiting near such black holes and analytically compute the…

General Relativity and Quantum Cosmology · Physics 2018-11-12 Minyong Guo , Niels A. Obers , Haopeng Yan

In this paper, the optical appearance of static and spherically symmetric hairy black holes is studied under the standard Einstein-Maxwell theory considering the p-power Yang-Mills term. During the research process, the specific case of…

General Relativity and Quantum Cosmology · Physics 2025-01-14 Zuting Luo , Meirong Tang , Zhaoyi Xu

This study explores spherically symmetric non-linear electrodynamics black holes and their effects on light propagation. We derive the governing metric, revealing radial coordinate dynamics within the event horizon. We analyze photon…

General Relativity and Quantum Cosmology · Physics 2024-02-06 Akhil Uniyal , Sayan Chakrabarti , Mohsen Fathi , Ali Övgün

Shadows of black holes surrounded by an optically thin emitting medium have been extensively discussed in the literature. The Hioki-Maeda algorithm is a simple recipe to characterize the shape of these shadows and determine the parameters…

High Energy Astrophysical Phenomena · Physics 2015-12-04 Lingyun Yang , Zilong Li

Investigations of shadows of astrophysical entities constitute a major source of insight into the evolution of compact objects. Such effects depend on the nature of the compact object and arise on account of the strong gravitational lensing…

General Relativity and Quantum Cosmology · Physics 2019-10-21 Muhammed Amir , Kimet Jusufi , Ayan Banerjee , Sudan Hansraj

In this paper, by exploring the photon motion in the region near the Bardeen black hole, the shadow and observation properties of the black hole surrounded by various accretion models are studied. We analyzed the changes in shadow imaging…

High Energy Physics - Theory · Physics 2022-08-17 Ke-Jian He , Sen Guo , Shuang-Cheng Tan , Guo-Ping Li

This study investigates the effects of higher dimensions on the observable properties of Schwarzschild-Tangherlini black holes, focusing on the photonsphere, shadow radius, deflection angles, and quasinormal modes (QNMs). By extending…

General Relativity and Quantum Cosmology · Physics 2025-06-27 Nikko John Leo S. Lobos , Anele M. Ncube , Reggie C. Pantig , Alan S. Cornell

Explicitly covariant analytical expressions are derived that describe the boundaries of shadows cast by massive particles scattered by a gravitating object. This covers scenarios with particles having effectively variable mass, such as…

General Relativity and Quantum Cosmology · Physics 2023-12-15 Kirill Kobialko , Igor Bogush , Dmitri Gal'tsov

In this paper, we discuss the effects of nonlinear electrodynamics (NED) on non-rotating black holes, parametrized by the field coupling parameter $\beta$ and magnetic charge parameter $P$ in detail. Particularly, we survey physical…

General Relativity and Quantum Cosmology · Physics 2022-01-06 Mert Okyay , Ali Övgün

We consider the rotating generalization of the Bardeen black hole solution in the presence of cloud of strings (CoS). The parameter space for which the black hole horizon exists is determined. We also study the static limit surface and the…

General Relativity and Quantum Cosmology · Physics 2023-11-01 Bijendra Kumar Vishvakarma , Dharm Veer Singh , Sanjay Siwach

This work is geared towards analysis of shadows cast by Kerr-de Sitter (KdS) and Kerr-de Sitter Revisited (RKdS) black holes. Considering observers in the vicinity of the static radius, we derive the impact parameters defining the apparent…

General Relativity and Quantum Cosmology · Physics 2022-05-17 Eunice Omwoyo , Humberto Belich , Júlio C. Fabris , Hermano Velten