Testing the Existence of Event Horizons against Rotating Reflecting Surfaces

Abstract

Recently the Event Horizon Telescope observed black holes at event horizon scales for the first time, enabling us to now test the existence of event horizons. Although event horizons have by definition no observable features, one can look for their non-existence. In that case, it is likely that there is some kind of surface, which like any other surface could absorb (and thermally emit) and/or reflect radiation. In this paper, we study the potential observable features of such rotating reflecting surfaces. We construct a general description of reflecting surfaces in arbitrary spacetimes. This is used to define specific models for static and rotating reflecting surfaces, of which we study the corresponding light paths and synthetic images. This is done by numerical integration of the geodesic equation and by the use of the general relativistic radiative transfer code RAPTOR. The reflecting surface creates an infinite set of ring-like features in synthetic images inside the photon ring. There is a central ring in the middle and higher order rings subsequently lie exterior to each other converging to the photon ring. The shape and size of the ring features change only slightly with the radius of the surface R, spin a and inclination i, resulting in all cases in features inside the 'shadow region'. We conclude that rotating reflecting surfaces have clear observable features and that the Event Horizon Telescope is able to observe the difference between reflecting surfaces and an event horizon for high reflectivities. Such reflecting surface models can be excluded, which strengthens the conclusion that the black hole shadow indeed indicates the existence of an event horizon.

arXiv comment14 pages, 10 figures; submitted to Astronomy and Astrophysics

References in corpus (47)

• Observation of Gravitational Waves from a Binary Black Hole Merger
• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies
• The Demography of Massive Dark Objects in Galaxy Centres
• Observational Evidence of AGN Feedback
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• Viewing the Shadow of the Black Hole at the Galactic Center
• Testing the nature of dark compact objects: a status report
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Is the gravitational-wave ringdown a probe of the event horizon?
• Tests of General Relativity with Binary Black Holes from the second LIGO-Virgo Gravitational-Wave Transient Catalog
• Gravitational Vacuum Condensate Stars
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Shadows and strong gravitational lensing: a brief review
• Echoes of ECOs: gravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
• Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole
• Jerusalem Lectures on Black Holes and Quantum Information
• Advection-Dominated Accretion and the Black Hole Event Horizon
• Advection-Dominated Accretion Model of Sagittarius A*: Evidence for a Black Hole at the Galactic Center
• Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole Images
• A new method for shadow calculations: application to parameterised axisymmetric black holes
• General relativistic magnetohydrodynamical simulations of the jet in M87
• The Black Hole Accretion Code
• The Shadow of a Spherically Accreting Black Hole
• Sharp bounds on $2m/r$ of general spherically symmetric static objects
• BlackHoleCam: fundamental physics of the Galactic center
• A Quantitative Test of the No-Hair Theorem with Sgr A* using stars, pulsars, and the Event Horizon Telescope
• How to tell an accreting boson star from a black hole
• The Event Horizon of Sagittarius A*
• Testing General Relativity with the Event Horizon Telescope
• Evidence for Jet Domination of the Nuclear Radio Emission in Low-luminosity Active Galactic Nuclei
• On The Nature of the Compact Dark Mass at the Galactic Center
• Constrained transport and adaptive mesh refinement in the Black Hole Accretion Code
• Where are all the gravastars? Limits upon the gravastar model from accreting black holes
• Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object
• Modeling non-thermal emission from the jet-launching region of M 87 with adaptive mesh refinement
• RAPTOR I: Time-dependent radiative transfer in arbitrary spacetimes
• Reflection of light from a uniformly moving mirror
• Distinguishing gravitational and emission physics in black-hole imaging: spherical symmetry
• Sgr A*: The Optimal Testbed of Strong-Field Gravity
• Towards VLBI Observations of Black Hole Structure
• Deep Horizon; a machine learning network that recovers accreting black hole parameters
• Rigidly rotating ZAMO surfaces in the Kerr spacetime