No observational proof of the black-hole event-horizon

Abstract

Recently, several ways of obtaining observational proof of the existence of black-hole horizons have been proposed. We argue here that such proof is fundamentally impossible: observations can provide arguments, sometimes very strong ones, in favour of the existence of the event horizon, but they cannot prove it. This applies also to future observations, which will trace very accurately the details of the spacetime metric of a body suspected of being a black hole.

4 pages, no figures, submitted to A&A Letters

References in corpus (6)

• A precise determination of angular momentum in the black hole candidate GRO J1655-40
• An unusually massive stellar black hole in the Galaxy
• Weyl Cohomology and the Effective Action for Conformal Anomalies
• 'Stable' QPOs and Black Hole Properties from Diskoseismology
• The X-ray Spectra of Black Hole X-ray Novae in Quiescence as Measured by Chandra
• Holonomy invariance, orbital resonances, and kilohertz QPOs

Cited by in corpus (159)

• Quasinormal modes of black holes and black branes
• Hot Accretion Flows Around Black Holes
• Testing General Relativity with Present and Future Astrophysical Observations
• The Galactic Center Massive Black Hole and Nuclear Star Cluster
• Testing the nature of dark compact objects: a status report
• Is the gravitational-wave ringdown a probe of the event horizon?
• Gravitational Vacuum Condensate Stars
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Foundations of Black Hole Accretion Disk Theory
• Calculating black hole shadows: Review of analytical studies
• Stable gravastars - an alternative to black holes?
• Advection-Dominated Accretion and the Black Hole Event Horizon
• Gravastars must have anisotropic pressures
• Stable dark energy stars
• Testing black hole candidates with electromagnetic radiation
• A New Simple Model for High Frequency Quasi Periodic Oscillations in Black Hole Candidates
• How to tell a gravastar from a black hole
• Shadows of spherically symmetric black holes and naked singularities
• General parametrization of axisymmetric black holes in metric theories of gravity
• Gravitational Condensate Stars: An Alternative to Black Holes
• Jet-dominated states: an alternative to advection across black hole event horizons in `quiescent' X-ray binaries
• Can the supermassive objects at the centers of galaxies be traversable wormholes? The first test of strong gravity for mm/sub-mm VLBI facilities
• Black Holes in Astrophysics
• A recipe for echoes from exotic compact objects
• New parametrization for spherically symmetric black holes in metric theories of gravity
• Into the lair: gravitational-wave signatures of dark matter
• Constraining the spin and the deformation parameters from the black hole shadow
• Singularity-free dark energy star
• Phenomenological aspects of black holes beyond general relativity
• Ergoregion instability of ultra-compact astrophysical objects
• Shadows of rotating wormholes
• Measuring the Kerr spin parameter of regular black holes from their shadow
• Gravitational wave signatures of the absence of an event horizon. I. Nonradial oscillations of a thin-shell gravastar
• Distinguishing black holes from naked singularities through their accretion disk properties
• The Gravitational-Wave Physics
• Stable gravastars with generalised exteriors
• Not quite a black hole
• Jet-dominated advective systems: radio and X-ray luminosity dependence on the accretion rate
• Shape and position of the shadow in the $\delta =2$ Tomimatsu-Sato space-time
• Gravastars supported by nonlinear electrodynamics
• The Milky Way's Supermassive Black Hole: How good a case is it? A Challenge for Astrophysics & Philosophy of Science
• On The Nature of the Compact Dark Mass at the Galactic Center
• Gravitational wave echoes through new windows
• On the ergoregion instability in rotating gravastars
• Exotic Compact Objects and How to Quench their Ergoregion Instability
• Non-linear resonance in the accretion disk of a millisecond pulsar
• Testing the Kerr black hole hypothesis
• Measuring mass and angular momentum of black holes with high-frequency quasi-periodic oscillations
• Accretion disk onto boson stars: a way to supplant black holes candidates
• Ergoregion instability of exotic compact objects: electromagnetic and gravitational perturbations and the role of absorption
• Constraining Alternate Models of Black Holes: Type I X-ray Bursts on Accreting Fermion-Fermion and Boson-Fermion Stars
• Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object
• Black hole mimickers: regular versus singular behavior
• Phantom stars and topology change
• On the Lack of Thermal Emission from the Quiescent Black Hole XTE J1118+480: Evidence for the Event Horizon
• Broad K$\alpha$ iron line from accretion disks around traversable wormholes
• Shadow images of Kerr-like wormholes
• Interior of a Schwarzschild black hole revisited
• Gravitational echoes from macroscopic quantum gravity effects
• K$\alpha$ iron line profile from accretion disks around regular and singular exotic compact objects
• Scalar field effects on the orbit of S2 star
• Oscillations of vertically integrated relativistic tori -II. Axisymmetric modes in a Kerr spacetime
• On the Correlated Spectral and Timing Properties of 4U 1636-53: an Atoll Source at High Accretion Rates
• Instability of hyper-compact Kerr-like objects
• Testing the nature of the black hole candidate in GRO J1655-40 with the relativistic precession model
• Gravitational-wave signatures of the absence of an event horizon. II. Extreme mass ratio inspirals in the spacetime of a thin-shell gravastar
• Likely formation of general relativistic radiation pressure supported stars or "eternally collapsing objects"
• Observational properties of relativistic fluid spheres with thin accretion disks
• Where does the physics of extreme gravitational collapse reside?
• Measuring the Kerr spin parameter of a non-Kerr compact object with the continuum-fitting and the iron line methods
• Supermassive black holes or boson stars? Hair counting with gravitational wave detectors
• Implications of the Gravitational Wave Event GW150914
• The final stages of accretion onto non-Kerr compact objects
• Constraining the charge of the Galactic centre black hole
• Phenomenology of GUP stars
• Self-bound CFL stars in binary systems : are they "hidden" among the black hole candidates?
• The Transient Gravitational-Wave Sky
• Exponential fading to white of black holes in quantum gravity
• Towards the use of the most massive black hole candidates in AGN to test the Kerr paradigm
• Constraint on the quadrupole moment of super-massive black hole candidates from the estimate of the mean radiative efficiency of AGN
• Characterization of echoes: A Dyson-series representation of individual pulses
• Testing the Kerr Nature of Black Hole Candidates using Iron Line Spectra in the CPR Framework
• Echoes from phantom wormholes
• The neutron star soft X-ray transient 1H1905+000 in quiescence
• Bounded excursion stable gravastars and black holes
• On an alternative mechanism for the black hole echoes
• Stellar disruption events support the existence of the black hole event horizon
• Towards VLBI Observations of Black Hole Structure
• Curvature Invariants and Lower Dimensional Black Hole Horizons
• Low-rate accretion onto isolated stellar mass black holes
• Slowly rotating super-compact Schwarzschild stars
• The Rates of type I X-ray Bursts from Transients Observed with RXTE: Evidence for Black Hole Event Horizons
• Echoes from Asymmetric Wormholes and Black Bounce
• How loud are echoes from exotic compact objects?
• Evolution of the spin parameter of accreting compact objects with non-Kerr quadrupole moment
• Semiclassical relativistic stars
• Testing the nature of the supermassive black hole candidate in SgrA* with light curves and images of hot spots
• Astrometric observations of X-ray binaries using very long baseline interferometry
• On Intrinsic Magnetic Moments In Black Hole Candidates
• Gravitational Vacuum Condensate Stars
• Observational Evidence for Black Holes
• Observational evidence for the formation of trapping horizons in astrophysical black holes
• Echoes from a singularity
• On the instability of ultracompact horizonless spacetimes
• Massive Black Hole Science with eLISA
• Distinguishing Brans-Dicke-Kerr type naked singularities and black holes with their thin disk electromagnetic radiation properties
• Anisotropic charged dark energy star
• On the Origin of the Radio/X-Ray Luminosity Correlation in Black Hole Candidates
• Physics of accretion flows around compact objects
• Can mixed star-plus-wormhole systems mimic black holes?
• Spicing up the recipe for echoes from exotic compact objects: orbital differences and corrections in rotating backgrounds
• Shadows around the q-metric
• Dark energy stars: Stable configurations
• Gravitational atoms in the braneworld scenario
• Horizon closeness bounds for static black hole mimickers
• Electromagnetic tests of horizonless rotating black hole mimickers
• Nomen non est omen: Why it is too soon to identify ultra-compact objects as black holes
• Magnetized tori in the background of a deformed compact object
• New Horizons in Gravity: Dark Energy and Condensate Stars
• X-ray Bursts in Neutron Star and Black Hole Binaries from USA and RXTE Data: Detections and Upper Limits
• Particle creation in gravitational collapse to a horizonless compact object
• A note on the observational evidence for the existence of event horizons in astrophysical black hole candidates
• Particle Dynamics and Quasi-Periodic Oscillations in the GUP-Modified Schwarzschild Spacetime: Constraint Using Micro-Quasars Data
• Gravitational lensing and accretion disk imaging of a Buchdahl dense core
• A Critical Assessment of Black Hole Solutions With a Linear Term in Their Redshift Function
• Charged Gravastar in a Dark Energy Universe
• Vacuum fluctuation inside a star and their consequences for neutron stars, a simple model
• Lorentz violation with an invariant minimum speed as foundation of the Gravitational Bose Einstein Condensate of a Dark Energy Star
• The Interpretations For the Low and High Frequency QPO Correlations of X-ray Sources Among White Dwarfs, Neutron Stars and Black Holes
• Burst particle creation in gravitational collapse to a horizonless compact object
• Selfgravitation in a general-relativistic accretion of steady fluids
• Scattering of particles by deformed non-rotating black holes
• The Fredholm Approach to Charactize Gravitational Wave Echoes
• Dynamics of charged particles and quasi-periodic oscillations in the vicinity of a distorted, deformed compact object embedded in a uniform magnetic field
• Hybrid imploding scalar and ads spacetime
• Selected Chapters on Active Galactic Nuclei as Relativistic Systems
• Magnetised relativistic accretion disc around a spinning, electrically charged, accelerating black hole: case of C-metric
• Quantum Gravitational Hair in Gravastars and Observational Tests
• Probing the horizon of black holes with gravitational waves
• Beyond Buchdahl's limit: bilayered stars and thin-shell configurations
• AdS gravastar and bulk-cone singularities
• Observational signatures of Rotating compact objects in Plasma space-time
• Why the astrophysical Black Hole Candidates may not be black holes at all
• Black Holes or Frozen Stars? A Viable Theory of Gravity without Black Holes
• Effect of an external mass distribution on the magnetized accretion disk
• Structure of the thin disk in the background of a distorted naked singularity versus a distorted static black hole
• How to distinguish an actual astrophysical magnetized black hole mimicker from a true (theoretical) black hole
• Predictions on observing hot holographic quark star with gravitational waves
• Connection between Symmetrical Special Relativity and the Gravitational Bose Einstein Condensate of a Gravastar/Dark Energy Star: Are there singularities in spacetime like black holes?
• Black hole masking and black hole thermodynamics
• Constraints on horizonless objects after the EHT observation of Sagittarius A*
• Quasi-periodic oscillatory motion of particles orbiting a distorted deformed compact object
• Asymptotic Freedom and Vacuum Polarization Determine the Astrophysical End State of Relativistic Gravitational Collapse: Quark--Gluon Plasma Star Instead of Black Hole
• Nonuniqueness of stationary accretion in the Shakura model
• Focusing versus defocusing properties of truly naked black holes
• Comment to ''On Anisotropic Dark Energy Stars''
• Light ring images of double photon spheres in black hole and wormhole space-times
• Decoding Horizonless Spacetime: Plasma-Induced Features in a Rotating Wormhole Shadow
• Scattering of massive particles from black holes and naked singularities