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The need for a consistent quantum evolution for black holes has led to proposals that their semiclassical description is modified not just near the singularity, but at horizon or larger scales. If such modifications extend beyond the…

High Energy Astrophysical Phenomena · Physics 2018-04-25 Steven B. Giddings , Dimitrios Psaltis

Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This polarized synchrotron radiation probes the structure of magnetic fields and the…

High Energy Astrophysical Phenomena · Physics 2021-05-06 The Event Horizon Telescope Collaboration

We show how Event Horizon Telescope (EHT) observations of the supermassive object at the center of M87 can constrain deviations from General Relativity (GR) in a relatively model-independent way. We focus on the class of theories whose…

General Relativity and Quantum Cosmology · Physics 2020-08-26 Markus Rummel , C. P. Burgess

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

The Event Horizon Telescope (EHT) has significantly advanced our ability to study black holes, achieving unprecedented spatial resolution and revealing horizon-scale structures. Notably, these observations feature a distinctive dark…

High Energy Physics - Phenomenology · Physics 2025-09-22 Yifan Chen , Ran Ding , Yuxin Liu , Yosuke Mizuno , Jing Shu , Haiyue Yu , Yanjie Zeng

The concept of a new space very long baseline interferometry system named the Event Horizon Imager (EHI) has been proposed to dramatically improve black hole imaging and provide precise tests of the theory of general relativity. We…

High Energy Astrophysical Phenomena · Physics 2026-02-04 Anastasia Shlentsova , Freek Roelofs , Sara Issaoun , Jordy Davelaar , Heino Falcke

We introduce a new library of 535,194 model images of the supermassive black holes and Event Horizon Telescope (EHT) targets Sgr A* and M87*, computed by performing general relativistic radiative transfer calculations on general…

High Energy Astrophysical Phenomena · Physics 2023-02-22 Richard Qiu , Angelo Ricarte , Ramesh Narayan , George N. Wong , Andrew Chael , Daniel Palumbo

The black hole spacetime is described by general relativity and characterized by two quantities: the black hole mass and spin. Black hole spin measurement requires information from the vicinity of the event horizon, which is spatially…

High Energy Astrophysical Phenomena · Physics 2020-01-08 Kotaro Moriyama , Shin Mineshige , Mareki Honma , Kazunori Akiyama

The Event Horizon Telescope (EHT) Collaboration produced the first image of the apparent shadow of the central black hole of Sagittarius\,A$^*$ (\sgra). \sgra source structure varies significantly on timescales shorter than the duration of…

High Energy Astrophysical Phenomena · Physics 2026-01-26 Braden J. Marazzo-Nowicki , Paul Tiede , Dominic O. Chang , Daniel C. M. Palumbo , Michael D. Johnson

General relativistic magnetohydrodynamic (GRMHD) simulations of accretion disks and jets associated with supermassive black holes show variability on a wide range of timescales. On timescales comparable to or longer than the gravitational…

High Energy Astrophysical Phenomena · Physics 2017-10-04 Freek Roelofs , Michael D. Johnson , Hotaka Shiokawa , Sheperd S. Doeleman , Heino Falcke

The study of astrophysical phenomena like black hole shadows is an effective approach to properly understand the modified gravity and explore its validity. Motivated by recent astrophysical observations, we consider a black hole (BH) in…

General Relativity and Quantum Cosmology · Physics 2025-03-20 Khadije Jafarzade , Zeynab Bazyar , Mubasher Jamil

We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of ~40 micro-as, consistent with the size and shape of the lensed…

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

The black hole in the center of the Galaxy, associated with the compact source Sagittarius A* (Sgr A*), is predicted to cast a shadow upon the emission of the surrounding plasma flow, which encodes the influence of general relativity in the…

We analyze two 3D general-relativistic magnetohydrodynamic accretion simulations in the context of how they would manifest in Event Horizon Telescope (EHT) observations of supermassive black holes. The two simulations differ only in whether…

High Energy Astrophysical Phenomena · Physics 2020-05-06 Christopher J. White , Jason Dexter , Omer Blaes , Eliot Quataert

Faraday rotation has been seen at millimeter wavelengths in several low luminosity active galactic nuclei, including Event Horizon Telescope (EHT) targets M87* and Sgr A*. The observed rotation measure (RM) probes the density, magnetic…

High Energy Astrophysical Phenomena · Physics 2020-10-07 Angelo Ricarte , Ben S. Prather , George N. Wong , Ramesh Narayan , Charles Gammie , Michael Johnson

In 2017 April, the Event Horizon Telescope (EHT) observed the near-horizon region around the supermassive black hole at the core of the M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source…

High Energy Astrophysical Phenomena · Physics 2021-05-05 The Event Horizon Telescope Collaboration

The polarized images of the supermassive black hole Messier 87* (M87*) produced by the Event Horizon Telescope (EHT) provide a direct view of the near-horizon emission from a black hole accretion and jet system. The EHT theoretical analysis…

High Energy Astrophysical Phenomena · Physics 2024-07-16 Daniel C. M. Palumbo , Michi Baubock , Charles F. Gammie

The Event Horizon Telescope (EHT) is a millimeter-wavelength, very-long-baseline interferometry (VLBI) experiment that is capable of observing black holes with horizon-scale resolution. Early observations have revealed variable…

High Energy Astrophysical Phenomena · Physics 2016-12-20 Junhan Kim , Daniel P. Marrone , Chi-kwan Chan , Lia Medeiros , Feryal Özel , Dimitrios Psaltis

We demonstrate the unprecedented capabilities of the Event Horizon Telescope (EHT) to image the innermost dark matter profile in the vicinity of the supermassive black hole at the center of the M87 radio galaxy. We present the first model…

Astrophysics of Galaxies · Physics 2018-01-31 Thomas Lacroix , Mansour Karami , Avery E. Broderick , Joseph Silk , Celine Boehm

The Event Horizon Telescope (EHT), a global sub-millimeter wavelength very long baseline interferometry array, is now resolving the innermost regions around the supermassive black holes Sgr A* and M87. Using black hole images from both…

High Energy Astrophysical Phenomena · Physics 2015-06-23 Angelo Ricarte , Jason Dexter