Rotating black holes with primary scalar hair in beyond Horndeski gravity produce shadows whose diameter increases for negative Q and whose distortion increases for positive Q, with EHT bounds on M87* restricting but not ruling out the (a, Q) parameter space.
hub
First M87 Event Horizon Telescope Results. II. Array and Instrumentation
15 Pith papers cite this work. Polarity classification is still indexing.
15
Pith papers citing it
abstract
The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength of ~1.3 mm, EHT angular resolution (lambda/D) is ~25 micro-as, which is sufficient to resolve nearby supermassive black hole candidates on spatial and temporal scales that correspond to their event horizons. With this capability, the EHT scientific goals are to probe general relativistic effects in the strong-field regime and to study accretion and relativistic jet formation near the black hole boundary. In this Letter we describe the system design of the EHT, detail the technology and instrumentation that enable observations, and provide measures of its performance. Meeting the EHT science objectives has required several key developments that have facilitated the robust extension of the VLBI technique to EHT observing wavelengths and the production of instrumentation that can be deployed on a heterogeneous array of existing telescopes and facilities. To meet sensitivity requirements, high-bandwidth digital systems were developed that process data at rates of 64 gigabit/s, exceeding those of currently operating cm-wavelength VLBI arrays by more than an order of magnitude. Associated improvements include the development of phasing systems at array facilities, new receiver installation at several sites, and the deployment of hydrogen maser frequency standards to ensure coherent data capture across the array. These efforts led to the coordination and execution of the first Global EHT observations in 2017 April, and to event-horizon-scale imaging of the supermassive black hole candidate in M87.
hub tools
citation-role summary
background 2
method 1
citation-polarity summary
representative citing papers
VAPOLA releases multi-epoch multi-band ALMA full-Stokes products and polarimetric fits for AGN and Sgr A* via an automated pipeline and web portal.
Machine learning on simulated images identifies that flux eruption events cause more diffuse, polarized, lower-flux millimeter emission with decreased Q-U loop rotation rate, achieving ~80% accuracy with random forests on summary statistics.
Three distinct non-minimal curvature-EM couplings produce different enlargements or reductions of black hole shadows and alter photon ring separations in characteristic ways.
EHT dimensionless shadow diameters plus stellar-dynamical mass priors constrain Einasto central density to ρ₀ ≲ 10^{-11} M⊙/pc³ (1σ) for Sgr A*, with weaker bounds for M87*.
Boson stars in teleparallel gravity with nonminimal coupling show negative energy density and energy-condition violation in excited states, with EMRI waveforms potentially detectable by LISA.
Energy extraction efficiency via Comisso-Asenjo reconnection in N=2 U(1)^2 gauged supergravity black holes exceeds the Kerr limit (η>1.495) for certain parameter combinations at lower spins.
Calculations indicate AMEGO-X could detect PBH transits within 0.1 AU while HAWC and LHAASO could observe explosions out to 0.1-0.5 pc, with future events at ~1000 AU potentially producing measurable electromagnetic signals unlike the 2023 KM3NeT neutrino candidate.
Analysis of how string cloud parameter a and dark matter parameter α alter MBO, ISCO, periodic orbits indexed by q, and the gravitational waveforms generated by those orbits in a modified Schwarzschild spacetime.
Photon-axion conversion near Kerr black holes produces dimming of photon spectral luminosity that increases with black hole spin, magnetic field strength, and photon-axion coupling, most efficiently at high frequencies.
Tidal forces in the Simpson-Visser spacetime produce Roche radii for stars that depend on observer type and regularization, with some disruptions occurring outside the event horizon for supermassive black holes.
Rotating Ayón-Beato–García black holes cast smaller, spin-asymmetric shadows whose diameters, compared with EHT data, bound the nonlinear-electrodynamics charge while leaving Kerr viable.
In Kruglov NED, small positive q can create stable photon orbits and reshape black-hole shadows and accretion images even when the metric stays close to Reissner–Nordström.
GRRT simulations of CFM braneworld black holes show nonmonotonic tidal-parameter effects on image morphology with normalized mismatches of order 10^3, indicating identification remains difficult even with ngEHT and BHEX.
The paper reports on the aims, activities, and conclusions of an early-career workshop focused on scientific overviews, transferable skills, and networking in gravitational physics.
citing papers explorer
-
Rotating Black Holes with Primary Scalar Hair: Shadow Signatures in Beyond Horndeski Gravity
Rotating black holes with primary scalar hair in beyond Horndeski gravity produce shadows whose diameter increases for negative Q and whose distortion increases for positive Q, with EHT bounds on M87* restricting but not ruling out the (a, Q) parameter space.
-
VAPOLA -- A multi-year, multi-band polarization survey of AGN and Sgr A* at mm wavelengths with ALMA I. Survey Overview and Science-Ready Archival Products
VAPOLA releases multi-epoch multi-band ALMA full-Stokes products and polarimetric fits for AGN and Sgr A* via an automated pipeline and web portal.
-
Identifying Observational Signatures of Flux Eruption Events in Supermassive Black Hole Accretion Flows with Machine Learning
Machine learning on simulated images identifies that flux eruption events cause more diffuse, polarized, lower-flux millimeter emission with decreased Q-U loop rotation rate, achieving ~80% accuracy with random forests on summary statistics.
-
Photon rings and shadows of black holes with non-minimal couplings between curvature and electromagnetic field
Three distinct non-minimal curvature-EM couplings produce different enlargements or reductions of black hole shadows and alter photon ring separations in characteristic ways.
-
Observational Limits on Einasto Dark Matter Parameters from Event Horizon Telescope Images of Sgr A$^{*}$ and M87$^{*}$
EHT dimensionless shadow diameters plus stellar-dynamical mass priors constrain Einasto central density to ρ₀ ≲ 10^{-11} M⊙/pc³ (1σ) for Sgr A*, with weaker bounds for M87*.
-
Boson Stars in Teleparallel Gravity with a Nonminimally Coupled Field: The Violation of Energy Conditions and Gravitational Waveforms from EMRIs
Boson stars in teleparallel gravity with nonminimal coupling show negative energy density and energy-condition violation in excited states, with EMRI waveforms potentially detectable by LISA.
-
Comisso-Asenjo Mechanism in Rotating $\mathcal{N}=2,U(1)^2$ Gauged Supergravity Black Holes: Extended Comparison With Kerr Black Hole
Energy extraction efficiency via Comisso-Asenjo reconnection in N=2 U(1)^2 gauged supergravity black holes exceeds the Kerr limit (η>1.495) for certain parameter combinations at lower spins.
-
Electromagnetic Signatures From Primordial Black Holes in the Solar System
Calculations indicate AMEGO-X could detect PBH transits within 0.1 AU while HAWC and LHAASO could observe explosions out to 0.1-0.5 pc, with future events at ~1000 AU potentially producing measurable electromagnetic signals unlike the 2023 KM3NeT neutrino candidate.
-
Periodic orbits and gravitational waveforms around a Schwarzschild black hole with a cloud of strings embedded in perfect fluid dark matter
Analysis of how string cloud parameter a and dark matter parameter α alter MBO, ISCO, periodic orbits indexed by q, and the gravitational waveforms generated by those orbits in a modified Schwarzschild spacetime.
-
Dimming of Photon Ring due to Photon-Axion Conversion around Kerr Black Holes
Photon-axion conversion near Kerr black holes produces dimming of photon spectral luminosity that increases with black hole spin, magnetic field strength, and photon-axion coupling, most efficiently at high frequencies.
-
Roche limit and stellar disruption in the Simpson--Visser spacetime
Tidal forces in the Simpson-Visser spacetime produce Roche radii for stars that depend on observer type and regularization, with some disruptions occurring outside the event horizon for supermassive black holes.
-
Observational Signatures of Rotating Ay\'{o}n-Beato-Garc\'{i}a Black Holes: Shadows, Accretion Disks and Images
Rotating Ayón-Beato–García black holes cast smaller, spin-asymmetric shadows whose diameters, compared with EHT data, bound the nonlinear-electrodynamics charge while leaving Kerr viable.
-
Photon Propagation and Black Hole Imaging in Kruglov Nonlinear Electrodynamics
In Kruglov NED, small positive q can create stable photon orbits and reshape black-hole shadows and accretion images even when the metric stays close to Reissner–Nordström.
-
Images of Braneworld black holes with radiatively inefficient accretion flows
GRRT simulations of CFM braneworld black holes show nonmonotonic tidal-parameter effects on image morphology with normalized mismatches of order 10^3, indicating identification remains difficult even with ngEHT and BHEX.
-
The Early Career Workshop of GR-Amaldi 2025
The paper reports on the aims, activities, and conclusions of an early-career workshop focused on scientific overviews, transferable skills, and networking in gravitational physics.