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The first image of black hole in M87 galaxy taken by Event Horizon Telescope shows that directed observation of supermassive black holes would be a promising way to test general relativity in strong gravity field regime. In order to…

General Relativity and Quantum Cosmology · Physics 2020-04-17 Zhe Chang , Qing-Hua Zhu

We study a limit of the Kerr-(A)dS spacetime in a general dimension where an arbitrary number of its rotational parameters is set equal. The resulting metric after the limit formally splits into two parts - the first part has the form of…

General Relativity and Quantum Cosmology · Physics 2022-03-02 Eliška Polášková , Pavel Krtouš

X-ray reflection spectroscopy is currently one of the leading techniques for studying the inner part of accretion disks around black holes, measuring black hole spins, and even testing fundamental physics in strong gravitational fields.…

High Energy Astrophysical Phenomena · Physics 2022-10-14 Swarnim Shashank , Shafqat Riaz , Askar B. Abdikamalov , Cosimo Bambi

The Event Horizon Telescope (EHT) images of the supermassive black hole at the center of the galaxy M 87 provided the first image of the accretion environment on horizon scales. General relativity predicts that the image of the shadow…

High Energy Astrophysical Phenomena · Physics 2022-12-14 Paul Tiede , Avery E. Broderick , Daniel C. M. Palumbo , Andrew Chael

The Event Horizon Telescope (EHT) collaboration unveiled event-horizon-scale images of the supermassive black holes (SMBHs) M87* and Sgr A*, revealing a dark brightness depression, namely the black hole shadow, whose shape and size may…

General Relativity and Quantum Cosmology · Physics 2023-07-27 Misba Afrin , Sushant G. Ghosh

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…

General Relativity and Quantum Cosmology · Physics 2021-07-07 Rajibul Shaikh , Kunal Pal , Kuntal Pal , Tapobrata Sarkar

Black hole solutions in general relativity come with pathologies such as singularity and mass inflation instability, which are believed to be cured by a yet-to-be-found quantum theory of gravity. Without such consistent description, one may…

General Relativity and Quantum Cosmology · Physics 2023-02-14 Rajes Ghosh , Mostafizur Rahman , Akash K Mishra

The compact dark objects with very large masses residing at the centres of galaxies are believed to be black holes. Due to the gravitational lensing effect, they would cast a shadow larger than their horizon size over the background, whose…

Astrophysics · Physics 2008-11-26 Lei Huang , Mike Cai , Zhi-Qiang Shen , Feng Yuan

Signatures of X-ray reprocessing (reflection) out of an accretion disk are commonly observed in the high-energy spectrum of accreting black holes, and can be used to probe the strong gravity region around these objects. In this paper, we…

General Relativity and Quantum Cosmology · Physics 2020-05-14 Jingyi Wang , Askar B. Abdikamalov , Dimitry Ayzenberg , Cosimo Bambi , Thomas Dauser , Javier A. Garcia , Sourabh Nampalliwar , James F. Steiner

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…

General Relativity and Quantum Cosmology · Physics 2023-02-06 Sushant G. Ghosh , Rahul Kumar Walia

We consider a Lorentz violating non-commutating Kerr-like spacetime and studied the superradiance effect and the shadow cast by the back hole. We extensively study the different aspects of the black hole associated with a generalized…

General Relativity and Quantum Cosmology · Physics 2022-04-22 Sohan Kumar Jha , Anisur Rahaman

Broad, skewed iron K$\alpha$ emission lines in the X-ray spectra of accreting black holes encode key information about the spacetime geometry of the innermost disk. While the Kerr metric is standard for spin measurements, horizonless…

High Energy Astrophysical Phenomena · Physics 2026-04-28 Cheng Liu , Hoongwah Siew , Hong-Xuan Jiang , Yosuke Mizuno , Tao Zhu

The recently obtained hairy Kerr black holes, due to additional sources or surrounding fluid, like dark matter, with conserved energy-momentum tensor, have a deviation $\alpha$ and primary hair $l_0$, apart from rotation parameter $a$ and…

General Relativity and Quantum Cosmology · Physics 2021-06-01 Misba Afrin , Rahul Kumar , Sushant G. Ghosh

In general relativity, astrophysical black holes are uniquely described by the Kerr metric. Observational tests of the Kerr nature of these compact objects and, hence, of general relativity, require a metric that encompasses a broader class…

General Relativity and Quantum Cosmology · Physics 2015-06-11 Tim Johannsen

With the recent release of the black hole image of Sgr A* alongside the earlier image of M87*, one can achieve an in-depth understanding of gravitational physics at the horizon scale. According to the Event Horizon Telescope (EHT)…

General Relativity and Quantum Cosmology · Physics 2024-05-06 Khadije Jafarzade , Seyed Hossein Hendi , Mubasher Jamil , Sebastian Bahamonde

The Event Horizon Telescope (EHT) collaboration recently unveiled the first image of the supermassive black hole M87*, which exhibited a ring of angular diameter $\theta_{d}=42 \pm 3 \mu as$, a circularity deviation $\Delta C \leq 0.1$, and…

General Relativity and Quantum Cosmology · Physics 2022-06-17 Misba Afrin , Sushant G. Ghosh

In this article, we present the thermodynamic and shadow properties of rotating black holes with global monopole charge. The angular diameter of Sgr A$^{*}$ black hole is 48.7 $\pm$ 7 $\mu as$, which is 8 $kps$ far away having a mass of $M…

General Relativity and Quantum Cosmology · Physics 2025-06-04 Balendra Pratap Singh , Md Sabir Ali

The EHT observation revealed event horizon-scale images of the supermassive black holes Sgr A* and M87* and these results are consistent with the shadow of a Kerr black hole as predicted by general relativity. However, Kerr-like rotating…

General Relativity and Quantum Cosmology · Physics 2024-10-10 Shafqat Ul Islam , Sushant G. Ghosh , Sunil D. Maharaj

In this study, we delve into the observational implications of rotating Loop Quantum Black Holes (LQBHs) within an astrophysical framework. We employ semi-analytical General Relativistic Radiative Transfer (GRRT) computations to study the…

General Relativity and Quantum Cosmology · Physics 2023-12-29 Hong-Xuan Jiang , Cheng Liu , Indu K. Dihingia , Yosuke Mizuno , Haiguang Xu , Tao Zhu , Qiang Wu

The image of the emission surrounding the black hole in the center of the Milky Way is predicted to exhibit the imprint of general relativistic (GR) effects, including the existence of a shadow feature and a photon ring of diameter ~50…