Metric for rapidly spinning black holes suitable for strong-field tests of the no-hair theorem
By T. Johannsen, Dimitrios Psaltis. 2011
268 citations recorded by the source corpus.
According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric deviations from the Kerr metric have been suggested to study observational signatures in both the electromagnetic and gravitational-wave spectra that differ from the expected Kerr signals. Because of the no-hair theorem, however, such spacetimes cannot be regular everywhere outside the event horizons, if they are solutions to the Einstein field equations; they are often characterized by naked singularities or closed timelike loops in the regions of the spacetime that are accessible to an external observer. For observational tests of the no-hair theorem that involve phenomena in the vicinity of the circular photon orbit or the innermost stable circular orbit around a black hole, these pathologies limit the applicability of the metrics only to compact objects that do not spin rapidly. In this paper, we construct a Kerr-like metric which depends on a set of free parameters in addition to its mass and spin and which is regular everywhere outside of the event horizon. We derive expressions for the energy and angular momentum of a particle on a circular equatorial orbit around the black hole and compute the locations of the innermost stable circular orbit and the circular photon orbit. We demonstrate that these orbits change significantly for even moderate deviations from the Kerr metric. The properties of our metric make it an ideally suited spacetime to carry out strong-field tests of the no-hair theorem in the electromagnetic spectrum using the properties of accretion flows around astrophysical black holes of arbitrary spin.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/3c2959bbf631c47908164bf6a8f70a843cb0301f
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Citations in the corpus
- Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets (2013, methodology): “…theory of black holes, and for ultimately attempting tests of the no-hair theorem by, e.g., observing deviations from the multipoles predicted by the Kerr metric, all of which are functions of just the two parameters a ∗ and M (Vigeland & Hughes 2010; Johannsen & Psaltis 2010, 2011; Bambi 2013).”
- Superradiance: Energy Extraction, Black-Hole Bombs and Implications for Astrophysics and Particle Physics (2015, background): “Another strategy consists in considering phenomenological nonKerr geometries which are not necessarily solutions of any specific theory [255, 256].”
- Superradiance (2015, background): “Another strategy consists in considering phenomenological nonKerr geometries which are not necessarily solutions of any specific theory [324, 325].”
- Testing black hole candidates with electromagnetic radiation (2015, methodology): “Consistently with Johannsen & Psaltis (2011b), any resonance model can measure just one number of the spacetime geometry.”
- The black hole accretion code (2016, methodology): “For example, the coefficients in the Rezzolla-Zhidenko parametrization for the Johannsen-Psaltis [103] metric and for Einstein-Dilaton BHs [104] have already been provided in [101].”
- PHOTON RINGS AROUND KERR AND KERR-LIKE BLACK HOLES (2013, methodology): “This metric depends on four sets of deviation functions and describes a black hole for all values of the spin |a| ≤ GM/c2.”
- Phenomenological aspects of black holes beyond general relativity (2018, background): “In principle one would need to introduce a series of functions (t, r) to describe different decaying tails for different coefficients of the metric [88].”