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The images of supermassive black holes captured by the Event Horizon Telescope (EHT) collaboration have allowed us to have access to the physical processes that occur in the vicinity of the event horizons of these objects. This has enabled…

General Relativity and Quantum Cosmology · Physics 2023-11-14 Gaston Giribet , Emilio Rubin de Celis , Pedro Schmied

The goal of the Event Horizon Telescope (EHT) is to provide spatially resolved images of Sgr A*, the source associated with the Galactic Center black hole. Because Sgr A* varies on timescales short compared to an EHT observing campaign, it…

High Energy Astrophysical Phenomena · Physics 2017-09-06 Hotaka Shiokawa , Charles F. Gammie , Sheperd S. Doeleman

In anticipation of future multi-frequency observations of black hole with the Next Generation Event Horizon Telescope (ngEHT), we construct spectral images of a thin accretion disk around a spherically symmetric black hole immersed in cold,…

General Relativity and Quantum Cosmology · Physics 2025-06-25 Kirill Kobialko , Dmitri Gal'tsov , Alexey Molchanov

We show that interferometry can be applied to study irregular, rapidly rotating structures, as are expected in the turbulent accretion flow near a black hole. Specifically, we analyze the lagged covariance between interferometric baselines…

Instrumentation and Methods for Astrophysics · Physics 2015-11-11 Michael D. Johnson , Abraham Loeb , Hotaka Shiokawa , Andrew A. Chael , Sheperd S. Doeleman

Accreting black holes tend to display a characteristic dark central region called the black-hole shadow, which depends only on spacetime/observer geometry and which conveys information about the black hole's mass and spin. Conversely, the…

High Energy Astrophysical Phenomena · Physics 2020-11-10 Thomas Bronzwaer , Jordy Davelaar , Ziri Younsi , Monika Mościbrodzka , Héctor Olivares , Yosuke Mizuno , Jesse Vos , Heino Falcke

The initial data from the Event Horizon Telescope (EHT) on M87$^*$, the supermassive black hole at the center of the M87 galaxy, provide direct observational information on its mass, spin, and accretion disk properties. A combination of the…

Cosmology and Nongalactic Astrophysics · Physics 2019-07-12 Hooman Davoudiasl , Peter B. Denton

The images of the supermassive black holes Sgr A* and M87* by the Event Horizon Telescope (EHT) collaboration mark a special milestone in the history of the subject. For the first time we are able to see the shadow of black holes, testing…

High Energy Astrophysical Phenomena · Physics 2022-08-02 Heino Falcke

We test the possibility of using a convolutional neural network to infer the inclination angle of a black hole directly from the incomplete image of the black hole's shadow in the $uv$-plane. To this end, we develop a proof-of-concept…

High Energy Astrophysical Phenomena · Physics 2023-11-29 Anton A. Popov , Vladimir Strokov , Aleksey A. Surdyaev

Synthesis imaging of the black hole in the center of the Milky Way, Sgr A*, with the Event Horizon Telescope (EHT) rests on the assumption of a stationary image. We explore the limitations of this assumption using high-cadence GRMHD…

High Energy Astrophysical Phenomena · Physics 2018-08-15 Lia Medeiros , Chi-kwan Chan , Feryal Ozel , Dimitrios Psaltis , Junhan Kim , Daniel P. Marrone , Aleksander Sadowski

We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We develop and fit geometric crescent models (asymmetric rings with interior brightness…

Astrophysics of Galaxies · Physics 2019-07-08 The Event Horizon Telescope Collaboration

As one of the nearest and most dormant supermassive black holes (SMBHs), M31* provides a rare but promising opportunity for studying the physics of black hole accretion and feedback at the quiescent state. Previous Karl G. Jansky Very Large…

Astrophysics of Galaxies · Physics 2023-08-09 Sijia Peng , Zhiyuan Li , Lorant O. Sjouwerman , Yang Yang , Wu Jiang , Zhi-qiang Shen

Thanks to the release of the extraordinary EHT image of shadow attributed to the M87* supermassive black hole (SMBH), we have a novel window to assess the validity of fundamental physics in the strong-field regime. Motivated by this, we…

General Relativity and Quantum Cosmology · Physics 2021-09-22 Mohsen Khodadi , Gaetano Lambiase , David F. Mota

In this paper we use the imaging results of M87* from the EHT to calculate the rotational velocity of the inner edge of the accretion disk and find a value of $\sim$0.14c. We then calculate the dimensionless spin parameter, $a$, of the…

High Energy Astrophysical Phenomena · Physics 2025-05-26 Michael Drew , Joshua S. Stanway , Brett A. Patterson , Timothy J. Walton , Derek Ward-Thompson

Black hole (BH) shadow observations and gravitational wave astronomy have become crucial approaches for exploring BH physics and testing gravitational theories in extreme environments. This paper investigates the charged black hole with…

General Relativity and Quantum Cosmology · Physics 2025-09-16 Lai Zhao , Meirong Tang , Zhaoyi Xu

The images of supermassive black holes in M87 and our galaxy captured by the Event Horizon Telescope (EHT) might open up a new way for exploring black hole physics at the horizon scale. Theoretically, this could provide insights into…

General Relativity and Quantum Cosmology · Physics 2024-03-15 Qing-Hua Zhu

It has long been thought that black hole accretion flows are driven by magnetohydrodynamic (MHD) turbulence, and there are now many general relativistic global simulations illustrating the dynamics of this process. However, many challenges…

High Energy Astrophysical Phenomena · Physics 2026-03-11 Chris Nagele , Julian H. Krolik , Rongrong Liu , Brooks E. Kinch , Jeremy D. Schnittman

In this study, we have considered the Kerr-like black hole (BH) model in Horndeski gravity and analyse the visual characteristics of shadow images under two illumination models, such as a celestial light source and a thin accretion disk. To…

General Relativity and Quantum Cosmology · Physics 2025-09-09 Xiao-Xiong Zeng , Chen-Yu Yang , M. Israr Aslam , Rabia Saleem

We evaluate several neural-network architectures, both convolutional and recurrent, for gravitational-wave time-series feature extraction by performing point parameter estimation on noisy waveforms from binary-black-hole mergers. We build…

General Relativity and Quantum Cosmology · Physics 2024-04-23 Osvaldo Gramaxo Freitas , Juan Calderón Bustillo , José A. Font , Solange Nunes , Antonio Onofre , Alejandro Torres-Forné

The observable quantities that carry the most information regarding the structures of the images of black holes in the interferometric observations with the Event Horizon Telescope are the closure phases along different baseline triangles.…

High Energy Astrophysical Phenomena · Physics 2017-07-26 Lia Medeiros , Chi-kwan Chan , Feryal Özel , Dimitrios Psaltis , Junhan Kim , Daniel Marrone , Aleksander Sądowski

In view of the upcoming observations with the Event Horizon Telescope (EHT), we present our thoughts on the immediate environment of an astrophysical black hole. We are concerned that two approximations used in general relativistic…

High Energy Astrophysical Phenomena · Physics 2017-12-20 Ioannis Contopoulos
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