Three observables on a standardized segment of the Kerr critical curve uniquely fix spin a/M, inclination i, and segment location r_nl within the considered domain.
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First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
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abstract
The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87's large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.
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In the rotating García-Díaz NLED black hole the Fresnel quartic factorizes into two optical metrics whose critical families project to distinct contours Γ+ and Γ- whose angular separation is generated by the constitutive response and redistributed by spin.
In dRGT massive gravity, static spherically symmetric black holes exhibit zero, one, or two photon spheres whose topological charges and stability patterns differ from Einstein gravity and from horizonless compact objects.
3D GRMHD simulations of accretion onto a JMN-1 horizonless singularity produce a magnetically arrested disk with an accretion rate of ~3e-6 Eddington matching M87* observations and EHT-consistent images, plus central brightness inside the shadow as a discriminant from black holes.
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.
Steady GRMHD jets exhibit a universal near-horizon polarization pattern set only by black hole spin, with large-radius polarization angle following a collimation-determined power law and intermediate scales modified by plasma loading.
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.
When source variability is comparable to Kerr geodesic delay spreads, high-inclination fast- and slow-light curves can differ by tens of percent; brisk light retains leading lensing timing more cheaply.
Three distinct non-minimal curvature-EM couplings produce different enlargements or reductions of black hole shadows and alter photon ring separations in characteristic ways.
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.
Derives B*(d) and N*(d) for AGN jet cores from self-absorbed synchrotron emission model with power-law assumptions on Doppler factor, Lorentz factor, B, and N versus jet width d.
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.
Exponential IR f(T) gravity Model I alleviates Hubble tension but is disfavoured by combined Planck/ACT/SPT+DESI+Pantheon+ data; Model II is ruled out because background constraints force unphysical shifts in CMB parameters.
Quintessence parameter cq systematically shifts zoom-whirl periodic orbits and their numerical-kludge EMRI waveforms around a magnetically charged nonlinear-electrodynamics black hole into the LISA millihertz band.
Simulations of accreting black holes in standard and complex spacetimes indicate that magnetic geometry, quantum corrections, and binary dynamics influence flares, precession, photon rings, and multi-wavelength variability, with potential EHT constraints.
A recurring 0.03 Hz radio QPO was detected in the 2025 flare of GRS 1915+105 at >5.9 sigma in one epoch, identical across S- and X-bands and prior years, indicating an intrinsic accretion-jet timescale.
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.
Kerr-BR black hole images with magnetically coupled synchrotron emissivity show spin- and B-dependent shifts in the inner disk edge, altered lensing rings, and Doppler asymmetries, with retrograde cases displaying wider central depletion.
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.
EHT shadow observations constrain the Lorentz-violating parameter ℓ in Kalb-Ramond gravity for charged rotating black holes to roughly |ℓ| ≲ 0.1-0.2, with an upper bound ℓ ≲ 0.19 from Sgr A*.
Polarization signatures from GRMHD simulations of black hole accretion can help probe disk, corona, and jet properties when combined with X-ray polarimetry observations.
citing papers explorer
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Determining Kerr black hole spin and inclination from a segment of the critical curve in black hole images
Three observables on a standardized segment of the Kerr critical curve uniquely fix spin a/M, inclination i, and segment location r_nl within the considered domain.
-
Constitutive birefringence and critical curves in the rotating Garc\'ia--D\'iaz black hole
In the rotating García-Díaz NLED black hole the Fresnel quartic factorizes into two optical metrics whose critical families project to distinct contours Γ+ and Γ- whose angular separation is generated by the constitutive response and redistributed by spin.
-
Topological charge and black hole photon spheres in massive gravity
In dRGT massive gravity, static spherically symmetric black holes exhibit zero, one, or two photon spheres whose topological charges and stability patterns differ from Einstein gravity and from horizonless compact objects.
-
GRMHD accretion beyond the black hole paradigm: Light from within the shadow
3D GRMHD simulations of accretion onto a JMN-1 horizonless singularity produce a magnetically arrested disk with an accretion rate of ~3e-6 Eddington matching M87* observations and EHT-consistent images, plus central brightness inside the shadow as a discriminant from black holes.
-
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.
-
Polarization Architecture of Steady GRMHD Jets from the Horizon to Infinity
Steady GRMHD jets exhibit a universal near-horizon polarization pattern set only by black hole spin, with large-radius polarization angle following a collimation-determined power law and intermediate scales modified by plasma loading.
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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.
-
Light Propagation Prescriptions for Black Hole Movies
When source variability is comparable to Kerr geodesic delay spreads, high-inclination fast- and slow-light curves can differ by tens of percent; brisk light retains leading lensing timing more cheaply.
-
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.
-
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.
-
Magnetic field and plasma number density from radio and millimeter core measurements in AGN jets
Derives B*(d) and N*(d) for AGN jet cores from self-absorbed synchrotron emission model with power-law assumptions on Doppler factor, Lorentz factor, B, and N versus jet width d.
-
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.
-
Cosmological Viability of Exponential Infrared $f(T)$ Gravity
Exponential IR f(T) gravity Model I alleviates Hubble tension but is disfavoured by combined Planck/ACT/SPT+DESI+Pantheon+ data; Model II is ruled out because background constraints force unphysical shifts in CMB parameters.
-
Periodic Timelike Motion and Gravitational Wave Signatures around a Magnetically Charged Black Hole Surrounded by Quintessence
Quintessence parameter cq systematically shifts zoom-whirl periodic orbits and their numerical-kludge EMRI waveforms around a magnetically charged nonlinear-electrodynamics black hole into the LISA millihertz band.
-
GRMHD and GRRT Simulations of Black Hole Accretion: Flares, Precession, and Complex Spacetimes
Simulations of accreting black holes in standard and complex spacetimes indicate that magnetic geometry, quantum corrections, and binary dynamics influence flares, precession, photon rings, and multi-wavelength variability, with potential EHT constraints.
-
A 0.03 Hz Radio Quasi-periodic Oscillation During the 2025 Flare of GRS 1915+105
A recurring 0.03 Hz radio QPO was detected in the 2025 flare of GRS 1915+105 at >5.9 sigma in one epoch, identical across S- and X-bands and prior years, indicating an intrinsic accretion-jet timescale.
-
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.
-
Optical Appearance of the Kerr-Bertotti-Robinson Black Hole with a Magnetically Driven Synchrotron Emissivity Model
Kerr-BR black hole images with magnetically coupled synchrotron emissivity show spin- and B-dependent shifts in the inner disk edge, altered lensing rings, and Doppler asymmetries, with retrograde cases displaying wider central depletion.
-
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.
-
Probing Kalb-Ramond gravity with charged rotating black holes: constraints from EHT observations
EHT shadow observations constrain the Lorentz-violating parameter ℓ in Kalb-Ramond gravity for charged rotating black holes to roughly |ℓ| ≲ 0.1-0.2, with an upper bound ℓ ≲ 0.19 from Sgr A*.
-
Polarization Signatures from GRMHD Simulations of Black Hole Accretion
Polarization signatures from GRMHD simulations of black hole accretion can help probe disk, corona, and jet properties when combined with X-ray polarimetry observations.