Observational phenomena related to primordial Kerr superspinars

Stuchlík, Zdeněk; Schee, Jan

doi:10.1088/0264-9381/29/6/065002

Cited by 90 publications

(128 citation statements)

References 115 publications

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“…This situation is similar to those discovered in the field of Kerr naked singularity spacetimes [42], where the trapped photons can strongly influence the accretion phenomena, especially in the near-extreme Kerr naked singularity states [41,43,45,56]. We expect a similar strong influence in the K-S naked singularity spacetimes [31,35].…”

Section: Photon Circular Geodesicssupporting

confidence: 86%

“…For all of the considered phenomena related to the K-S naked singularities, an "antigravity" effect [31,35] plays a fundamental role; a similar situation has also been discovered in braneworld naked singularity spacetimes [36][37][38][39][40]. However, it seems to be different in comparison to the rotating Kerr naked singularity spacetimes [41][42][43][44][45][46][47][48]; for a detailed analysis of the magnetized thick discs see [49].…”

Section: Introductionmentioning

confidence: 85%

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Perfect fluid tori orbiting Kehagias–Sfetsos naked singularities

et al. 2015

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We construct perfect fluid tori in the field of the Kehagias-Sfetsos (K-S) naked singularities. These are spherically symmetric vacuum solutions of the modified Hořava quantum gravity, characterized by a dimensionless parameter ωM 2 , combining the gravitational mass parameter M of the spacetime with the Hořava parameter ω, reflecting the role of the quantum corrections. In dependence on the value of ωM 2 , the K-S naked singularities demonstrate a variety of qualitatively different behavior of their circular geodesics that is fully reflected in the properties of the toroidal structures, demonstrating clear distinction to the properties of the torii in the Schwarzschild spacetimes. In all of the K-S naked singularity spacetimes the tori are located above an "antigravity" sphere where matter can stay in a stable equilibrium position, which is relevant for the stability of the orbiting fluid toroidal accretion structures. The signature of the K-S naked singularity is given by the properties of marginally stable tori orbiting with the uniform distribution of the specific angular momentum of the fluid, l = const. In the K-S naked singularity spacetimes with ωM 2 > 0.2811, doubled tori with the same l = const can exist; mass transfer between the outer torus and the inner one is possible under appropriate conditions, while only outflow to the outer space is allowed in complementary conditions. In the K-S spacetimes with ωM 2 < 0.2811, accretion from cusped perfect fluid tori is not possible due to the non-existence of unstable circular geodesics.

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Section: Photon Circular Geodesicssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 85%

Perfect fluid tori orbiting Kehagias–Sfetsos naked singularities

et al. 2015

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“…Then we give the circular geodesics of the special new class with the magnetic Maxwell limit, discuss their properties, and compare them to the well-known Bardeen spacetime. We also give the frequencies of the radial and vertical epicyclic motion, as these frequencies could be relevant in explaining the high-frequency quasiperiodic oscillations [51][52][53] and could thus serve as a strong test of relevance of the regular solutions.…”

Section: Introductionmentioning

confidence: 99%

Generic rotating regular black holes in general relativity coupled to nonlinear electrodynamics

2017

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We construct regular rotating black hole and no-horizon spacetimes based on the recently introduced spherically symmetric generic regular black hole spacetimes related to electric or magnetic charge under nonlinear electrodynamics coupled to general relativity that for special values of the spacetime parameters reduce to the Bardeen and Hayward spacetimes. We show that the weak and strong energy conditions are violated inside the Cauchy horizons of these generic rotating black holes. We give the boundary between the rotating black hole and no-horizon spacetimes and determine the black hole horizons and the boundary of the ergosphere. We introduce the separated Carter equations for the geodesic motion in these rotating spacetimes. For the most interesting new class of the regular spacetimes, corresponding for magnetic charges to the Maxwell field in the weak field limit of the nonlinear electrodynamics, we determine the structure of the circular geodesics and discuss their properties. We study the epicyclic motion of a neutral particle moving along the stable circular orbits around the "Maxwellian" rotating regular black holes. We show that epicyclic frequencies measured by the distant observers and related to the oscillatory motion of the neutral test particle along the stable circular orbits around the rotating singular and regular Maxwellian black holes are always smaller than ones in the Kerr spacetime.

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“…More complex resonant phenomena in HF QPOs have to be expected in the field of Kerr superspinars (naked singularities), as shown in and Stuchlík & Schee (2012b). In the superspinar (or naked singularity) backgrounds, the optical effects also demonstrate considerable differences as compared with those generated in the field of black holes (Stuchlík & Schee 2010Virbhadra & Ellis 2002;Virbhadra & Keeton 2008;Takahashi & Harada 2010).…”

Section: Determination Of the Black Hole Spin From The Resonance Modelmentioning

confidence: 89%

Multi-resonance orbital model of high-frequency quasi-periodic oscillations: possible high-precision determination of black hole and neutron star spin

Stuchlík

Kotrlová

Török

2013

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129

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Context. Using known frequencies of the twin-peak high-frequency quasiperiodic oscillations (HF QPOs) and known mass of the central black hole, the black-hole dimensionless spin a can be determined by assuming a concrete version of the resonance model. However, a wide range of observationally limited values of the black hole mass implies low precision of the spin estimates. Aims. We discuss the possibility of higher precision for the black hole spin a measurements in the framework of a multi-resonance model inspired by observations of more than two HF QPOs in the black hole systems, which are expected to occur at two (or more) different radii of the accretion disc. This framework is also applied in a modified form to the neutron star systems. Methods. We determine the spin and mass dependence of the twin-peak frequencies with a general rational ratio n:m, assuming a non-linear resonance of oscillations with the epicyclic and Keplerian frequencies or their combinations. In the multi-resonant model, the twin-peak resonances are combined properly to give the observed frequency set. For the black hole systems we focus on the special case of duplex frequencies, when the top, bottom, or mixed frequency is common at two different radii where the resonances occur giving triple frequency sets. Results. The sets of triple frequency ratios and the related spin a are given. The resonances are considered up to n = 5 since excitation of higher order resonances is improbable. The strong resonance model for "magic" values of the black hole spin means that two (or more) versions of resonance could occur at the same radius, allowing cooperative effects between the resonances. For neutron star systems we introduce a resonant switch model that assumes switching of oscillatory modes at resonant points. Conclusions. In the case of doubled twin-peak HF QPOs excited at two different radii with common top, bottom, or mixed frequency, the black hole spin a is given by the triple frequency ratio set. The spin is determined precisely, but not uniquely, because the same frequency set could correspond to more than one concrete spin a. The black hole mass is given by the magnitude of the observed frequencies. The resonant switch model puts relevant limits on the mass and spin of neutron stars, and we expect a strong increase in the fitting procedure precision when different twin oscillatory modes are applied to data in the vicinity of different resonant points. We expect the multi-resonance model to be applicable to data from the planned LOFT or similar X-ray satellite observatory.

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Observational phenomena related to primordial Kerr superspinars

Cited by 90 publications

References 115 publications

Perfect fluid tori orbiting Kehagias–Sfetsos naked singularities

Perfect fluid tori orbiting Kehagias–Sfetsos naked singularities

Generic rotating regular black holes in general relativity coupled to nonlinear electrodynamics

Multi-resonance orbital model of high-frequency quasi-periodic oscillations: possible high-precision determination of black hole and neutron star spin

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