Super-spinning compact objects generated by thick accretion disks

Abstract

If astrophysical black hole candidates are the Kerr black holes predicted by General Relativity, the value of their spin parameter must be subject to the theoretical bound $|a_{\ast }|\le 1$. In this work, we consider the possibility that these objects are either non-Kerr black holes in an alternative theory of gravity or exotic compact objects in General Relativity. We study the accretion process when their accretion disk is geometrically thick with a simple version of the Polish doughnut model. The picture of the accretion process may be qualitatively different from the one around a Kerr black hole. The inner edge of the disk may not have the typical cusp on the equatorial plane any more, but there may be two cusps, respectively above and below the equatorial plane. We extend previous work on the evolution of the spin parameter and we estimate the maximum value of $a_{\ast }$ for the super-massive black hole candidates in galactic nuclei. Since measurements of the mean radiative efficiency of AGNs require $\eta >0.15$, we infer the "observational" bound $|a_{\ast }|\lesssim 1.3$, which seems to be quite independent of the exact nature of these objects. Such a bound is only slightly weaker than $|a_{\ast }|\lesssim 1.2$ found in previous work for thin disks.

1+16 pages, 4 figures. v2: refereed version. v3: indicated the corresponding author

References in corpus (20)

• Constraining Black Hole Spin Via X-ray Spectroscopy
• Relativistic X-ray Lines from the Inner Accretion Disks Around Black Holes
• A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem
• Apparent shape of super-spinning black holes
• Using LISA EMRI sources to test off-Kerr deviations in the geometry of massive black holes
• Test bodies and naked singularities: is the self-force the cosmic censor?
• A code to compute the emission of thin accretion disks in non-Kerr space-times and test the nature of black hole candidates
• Shape and position of the shadow in the $\delta =2$ Tomimatsu-Sato space-time
• Testing the space-time geometry around black hole candidates with the analysis of the broad K$\alpha$ iron line
• Probing the space-time geometry around black hole candidates with the resonance models for high-frequency QPOs and comparison with the continuum-fitting method
• How to observe a non-Kerr spacetime
• Spinning Loop Black Holes
• Evidence for Rapidly Spinning Black Holes in Quasars
• Attempt to find a correlation between the spin of stellar-mass black hole candidates and the power of steady jets: relaxing the Kerr black hole hypothesis
• Constraint on the quadrupole moment of super-massive black hole candidates from the estimate of the mean radiative efficiency of AGN
• Gravitational instabilities in Kerr space-times
• Testing the existence of regions of stable orbits at small radii around black hole candidates
• Testing the space-time geometry around black hole candidates with the available radio and X-ray data
• Evolution of the spin parameter of accreting compact objects with non-Kerr quadrupole moment
• Spinning super-massive objects in galactic nuclei up to $a_{\ast }>1$

Cited by in corpus (24)

• Testing black hole candidates with electromagnetic radiation
• Constraining the spin and the deformation parameters from the black hole shadow
• Measuring the Kerr spin parameter of regular black holes from their shadow
• Non-singular quantum-inspired gravitational collapse
• Broad K$\alpha$ iron line from accretion disks around traversable wormholes
• K$\alpha$ iron line profile from accretion disks around regular and singular exotic compact objects
• Destroying the event horizon of regular black holes
• Distinguishing Kerr naked singularities and black holes using the spin precession of a test gyro in strong gravitational fields
• Reflection spectra of thick accretion disks
• Singularity avoidance in quantum-inspired inhomogeneous dust collapse
• Spin precession in a black hole and naked singularity spacetimes
• High energy collision of two particles in wormhole spacetimes
• Modeling bias in supermassive black hole spin measurements
• Testing the existence of regions of stable orbits at small radii around black hole candidates
• Testing the nature of the supermassive black hole candidate in SgrA* with light curves and images of hot spots
• Horizonless spacetimes as seen by present and next-generation Event Horizon Telescope arrays
• Testing the Kerr nature of black hole candidates using iron line reverberation mapping in the CPR framework
• Super-spinning compact objects and models of high-frequency quasi-periodic oscillations observed in Galactic microquasars
• Quantum gravity lights up spinning black holes
• Testing a class of non-Kerr metrics with hot spots orbiting SgrA${}^{\ast }$
• Super-spinning compact objects and models of high-frequency quasi-periodic oscillations observed in Galactic microquasars. II. Forced resonances
• Near- and sub-solar-mass naked singularities and black holes from transmutation of white dwarfs
• Distinguishing Signature of Kerr-MOG Black Hole and Superspinar via Lense-Thirring Precession
• Tests of General Relativity using black hole X-ray data