Difficulties of Quantitative Tests of the Kerr-Hypothesis with X-Ray Observations of Mass Accreting Black Holes

Abstract

X-ray studies of stellar mass black holes in X-ray binaries and mass-accreting supermassive black holes in Active Galactic Nuclei have achieved a high degree of maturity and have delivered detailed information about the astrophysical sources and the physics of black hole accretion. In this article, I review recent progress made towards using the X-ray observations for testing the "Kerr hypothesis" that the background spacetimes of all astrophysical quasi-stationary black holes are described by the Kerr metric. Although the observations have indeed revealed clear evidence for relativistic effects in strong-field gravity, quantitative tests of the Kerr hypothesis still struggle with theoretical and practical difficulties. In this article, I describe several recently introduced test metrics and review the status of constraining the background spacetimes of mass accreting stellar mass and supermassive black holes with these test metrics. The main conclusion of the discussion is that astrophysical uncertainties are large compared to the rather small observational differences between the Kerr and non-Kerr metrics precluding quantitative constraints on deviations from the Kerr metric at this point in time. I conclude with discussing future progress enabled by more detailed numerical simulations and by future X-ray spectroscopy, timing, polarimetry, and interferometry missions.

Review paper from the General Relativity and Gravitation (GRG) Topical Collection "Testing the Kerr spacetime with gravitational-wave and electromagnetic observations" (Guest Editor: Emanuele Berti), accepted version, https://doi.org/10.1007/s10714-018-2419-8

References in corpus (40)

• The Confrontation between General Relativity and Experiment
• X-ray Properties of Black-Hole Binaries
• Constraining Black Hole Spin Via X-ray Spectroscopy
• X-ray reverberation around accreting black holes
• Relativistic X-ray Lines from the Inner Accretion Disks Around Black Holes
• Global General Relativistic MHD Simulation of a Tilted Black-Hole Accretion Disk
• A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem
• Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548
• Rotating Black Holes in Dilatonic Einstein-Gauss-Bonnet Theory
• A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass
• Photon Rings around Kerr and Kerr-like Black Holes
• Testing Accretion Disk Theory in Black Hole X-ray Binaries
• The Kerr Metric
• Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope using Sparse Modeling
• A Determination of the Spin of the Black Hole Primary in LMC X-1
• A systematic look at the Very High and Low/Hard state of GX 339-4: Constraining the black hole spin with a new reflection model
• A code to compute the emission of thin accretion disks in non-Kerr space-times and test the nature of black hole candidates
• Alternative explanations for extreme supersolar iron abundances inferred from the energy spectrum of Cygnus X-1
• Testing the space-time geometry around black hole candidates with the analysis of the broad K$\alpha$ iron line
• Constraints on the spacetime geometry around 10 stellar-mass black hole candidates from the disk's thermal spectrum
• Theory of gravitation theories: a no-progress report
• Detection of Time Lags Between Quasar Continuum Emission Bands based on Pan-STARRS Light-curves
• The Radiative Efficiency and Spectra of Slowly Accreting Black Holes from Two-Temperature GRRMHD Simulations
• Probing the geometry and motion of AGN coronae through accretion disc emissivity profiles
• Polarization signatures of strong gravity in AGN accretion discs
• A Consistent Picture Emerges: A Compact X-ray Continuum Emission Region in the Gravitationally Lensed Quasar SDSS J0924+0219
• How important is non-ideal physics in simulations of sub-Eddington accretion onto spinning black holes?
• Modelling the Extreme X-ray Spectrum of IRAS 13224-3809
• Measuring the Innermost Stable Circular Orbits of Supermassive Black Holes
• The X-ray Polarization of the Accretion Disk Coronae of Active Galactic Nuclei
• Spectroscopic evidence for a low-mass black hole in SWIFT J1753.5-0127
• Reflection From the Strong Gravity Regime in a z=0.658 Gravitationally Lensed-Quasar
• Alignment Timescale of the Microquasar GRO J1655-40
• Conservative GRMHD Simulations of Moderately Thin, Tilted Accretion Disks
• No Evidence for Bardeen-Petterson Alignment in GRMHD Simulations and Semi-Analytic Models of Moderately Thin, Prograde, Tilted Accretion Disks
• Predicting the X-ray polarization of type-2 Seyfert galaxies
• X-ray Probes of Black Hole Accretion Disks for Testing the No-Hair Theorem
• An observational method for fast stochastic X-ray polarimetry-timing
• Confronting models for the high-frequency QPOs with Lense-Thirring precession
• Constraining the Kerr parameters via X-ray reflection spectroscopy

Cited by in corpus (29)

• Towards precision measurements of accreting black holes using X-ray reflection spectroscopy
• Black hole mimicker hiding in the shadow: Optical properties of the $\gamma$-metric
• Direct constraints on ultra-light boson mass from searches for continuous gravitational waves
• Search for ultralight bosons in Cygnus X-1 with Advanced LIGO
• Modeling and searching for a stochastic gravitational-wave background from ultralight vector bosons
• Towards precision tests of general relativity with black hole X-ray reflection spectroscopy
• Can the dynamics of test particles around charged stringy black holes mimic the spin of Kerr black holes?
• Constraints on the spacetime metric around seven "bare" AGNs using X-ray reflection spectroscopy
• Testing the Kerr black hole hypothesis using X-ray reflection spectroscopy and a thin disk model with finite thickness
• Follow-up signals from superradiant instabilities of black hole merger remnants
• Does the gravitomagnetic monopole exist? A clue from a black hole x-ray binary
• Testing the Kerr Black Hole Hypothesis with GX 339-4 by a combined analysis of its thermal spectrum and reflection features
• New Constraints on the Spin of the Black Hole Cygnus X-1 and the Physical Properties of its Accretion Disk Corona
• Testing general relativity with the stellar-mass black hole in LMC X-1 using the continuum-fitting method
• Square Peg in a Circular Hole: Choosing the Right Ansatz for Isolated Black Holes in Generic Gravitational Theories
• Testing the Kerr hypothesis using X-ray reflection spectroscopy with NuSTAR data of Cygnus X-1 in the soft state
• About the Kerr nature of the stellar-mass black hole in GRS 1915+105
• Implications of Einstein-Maxwell dilaton-axion gravity from the black hole continuum spectrum
• Constraining the Johannsen deformation parameter ${\epsilon }_3$ with black hole X-ray data
• Experimental Relativity with Accretion Disk Observations
• Reflection features in the X-ray spectrum of Fairall 9 and implications for tests of general relativity
• The Effect of Microlensing On the Observed X-ray Energy Spectra of Gravitationally Lensed Quasars
• Electromagnetic signatures of strong-field gravity from accreting black holes
• Topical Collection: Testing the Kerr spacetime with gravitational-wave and electromagnetic observations
• The Relative Importance of Faraday Rotation and QED Birefringence for the Linear Polarization of X-rays from Mass Accreting Black Holes
• Observational appearance of Kaluza-Klein black holes
• Gravitation and General Relativity at King's College London
• Testing beyond-Kerr spacetimes with GWTC-3
• Testing General Relativity with Black Hole X-ray Data