Photon rings of spherically symmetric black holes and robust tests of non-Kerr metrics

Abstract

Under very general assumptions on the accretion flow geometry, images of a black hole illuminated by electromagnetic radiation display a sequence of photon rings (demagnified and rotated copies of the direct image) which asymptotically approach a purely theoretical critical curve - the outline of the black hole photon shell. To a distant observer, these images appear dominated by the direct emission, which forms a ring whose diameter is primarily determined by the effective radius of the emitting region. For that reason, connecting the image diameter seen by a distant observer to the properties of the underlying spacetime crucially relies on a calibration that necessarily depends on the assumed astrophysical source model. On the other hand, the diameter of the photon rings depends more on the detailed geometry of the spacetime than on the source structure. As such, a photon ring detection would allow for the spacetime metric to be probed in a less model-dependent way, enabling more robust tests of General Relativity (GR) and the Kerr hypothesis. Here we present the photon ring structure of several spherically symmetric black hole spacetimes and perform comparisons with the Schwarzschild/Kerr case. We offer our perspective on future tests of the spacetime metric with photon rings, discussing challenges and opportunities involved.

accepted in PRD

References in corpus (26)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• Black Hole Shadows, Photon Rings, and Lensing Rings
• Constraints on black-hole charges with the 2017 EHT observations of M87*
• Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole
• A new method for shadow calculations: application to parameterised axisymmetric black holes
• The Shadow of a Spherically Accreting Black Hole
• The Shape of the Black Hole Photon Ring: A Precise Test of Strong-Field General Relativity
• Lensing by Kerr Black Holes
• Observing the Inner Shadow of a Black Hole: A Direct View of the Event Horizon
• Quantum corrected black holes: quasinormal modes, scattering, shadows
• Can the EHT M87 results be used to test general relativity?
• Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object
• Reflection-asymmetric wormholes and their double shadows
• Measuring Spin from Relative Photon Ring Sizes
• Hybrid Very Long Baseline Interferometry Imaging and Modeling with Themis
• Fuzzball Shadows: Emergent Horizons from Microstructure
• Accurate mapping of spherically symmetric black holes in a parameterised framework
• Maximum Observable Blueshift from Circular Equatorial Kerr Orbiters
• Visibility of Black Hole Shadows in Low-luminosity AGN
• Extremely long baseline interferometry with Origins Space Telescope

Cited by in corpus (66)

• Key Science Goals for the Next-Generation Event Horizon Telescope
• Strong gravitational lensing and shadow constraint from M87* of slowly rotating Kerr-like black hole
• Shadows of boson and Proca stars with thin accretion disks
• Imaging compact boson stars with hot-spots and thin accretion disks
• Shadows and photon rings of regular black holes and geonic horizonless compact objects
• Images and photon ring signatures of thick disks around black holes
• The Black Hole Explorer: Motivation and Vision
• Reference Array and Design Consideration for the next-generation Event Horizon Telescope
• Analytical study of higher-order ring images of accretion disk around black hole
• Rings and images of Horndeski hairy black hole illuminated by various thin accretions
• Observational properties of relativistic fluid spheres with thin accretion disks
• Photon ring test of the Kerr hypothesis: Variation in the ring shape
• Shape of higher-order images of equatorial emission rings around a Schwarzschild black hole: Analytical description with polar curves
• Photon rings as tests for alternative spherically symmetric geometries with thin accretion disks
• Observational predictions of LQG motivated polymerized black holes and constraints from Sgr A* and M87*
• Separating Astrophysics and Geometry in Black Hole Images
• Universal signatures of singularity-resolving physics in photon rings of black holes and horizonless objects
• Optical appearance of black holes surrounded by a dark matter halo
• Gravitational Lensing by Black Holes with Multiple Photon Spheres
• Testing Gravity with Black Hole Shadow Subrings
• The Black Hole Explorer: Photon Ring Science, Detection and Shape Measurement
• Multi-level images around Kerr-Newman black holes
• Geodesics and gravitational waves in chaotic extreme-mass-ratio inspirals: the curious case of Zipoy-Voorhees black-hole mimickers
• Strong deflection limit analysis of black hole lensing in inhomogeneous plasma
• Probing spacetime and accretion model for the Galactic Center: Comparison of Kerr and dilaton black hole shadows
• Constraining spherically symmetric metrics by the gap between photon rings
• The internal Faraday screen of Sagittarius A*
• The effect of scalar hair on the charged black hole with the images from accretions disk
• A novel test of gravity via black hole eikonal correspondence
• A Lensing-Band Approach to Spacetime Constraints
• Shadows near supermassive black holes: from a theoretical concept to GR test
• Strong deflection of massive particles in spherically symmetric spacetimes
• Is a black hole shadow a reliable test of the no-hair theorem?
• Orbital configurations of spaceborne interferometers for studying photon rings of supermassive black holes
• Distinguishing black holes with and without spontaneous scalarization in Einstein-scalar-Gauss-Bonnet theories via optical features
• Constraints on the black-hole charges of M87* and Sagittarius A* by changing rates of photon spheres can be relaxed
• The Existence and Distribution of Photon Spheres Near Spherically Symmetric Black Holes -- A Geometric Analysis
• Visions in Quantum Gravity
• Interferometric signature of higher-order images in a parametrized framework
• Compact objects in quadratic Palatini gravity generated by a free scalar field
• Spacetime Measurements with the Photon Ring
• Gravity versus astrophysics in black hole images and photon rings: Equatorial emissions and spherically symmetric space-times
• Conservative limits on the electric charge of Sgr A* in the Reissner-Nordstrom metric
• Climbing out of the shadows: building the distance ladder with black hole images
• Deep learning inference with the Event Horizon Telescope II. The Zingularity framework for Bayesian artificial neural networks
• Observational signatures from higher-order images of moving hotspots in accretion disks
• Semi-analytic studies of accretion disk and magnetic field geometry in M87*
• Effect of quantum deformed black hole on BH shadow in two-dimensional Dilaton gravity
• Photon ring autocorrelations from gravitational fluctuations around a black hole
• Overlapping of photon rings in black hole imaging
• A General Discussion on Photon Spheres in Different Categories of Spacetimes
• Observable strong field effects of extra spacetime dimension in the braneworld black hole
• Neutral particle collisions near Gibbons-Maeda-Garfinkle-Horowitz-Strominger black holes after shadow observations
• Shadow of quadrupole-deformed compact objects in a local dark matter shell
• Lensing, Shadow and Photon Rings in a Magnetized Black Hole Spacetime
• Probing Observable Features of Lorentz violation in Low-Energy Hořava Gravity with Accretion Disk Images of Black Hole
• Particle motion around luminous neutron stars: effects of deviation from Schwarzschild spacetime
• Auto- and cross-correlations for multiple images of corotating hotspots in accretion disks
• Shadow of rotating black holes with consistent thermodynamics
• Toward Optimisation of a Sub-Terahertz Spaceborne VLBI Mission
• Extreme-Lensing Signatures Revealed by Correlations of Simulated Black-Hole Movies
• The science case and challenges of space-borne sub-millimeter interferometry
• Asymptotic Schwarzschild solutions in $f(R)$ gravity and their observable effects on the photon sphere of black holes
• Light ring images of double photon spheres in black hole and wormhole space-times
• Effect of primary scalar hair on black hole's strong lensing in Beyond Horndeski Gravity
• Multi-ring images of thin accretion disk of a regular naked compact object