Evolution of Kerr superspinars due to accretion counterrotating thin discs

Stuchlík, Zdeněk; Hledík, Stanislav; Truparova, K.

doi:10.1088/0264-9381/28/15/155017

Cited by 71 publications

(113 citation statements)

References 81 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: 86%

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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: 86%

Perfect fluid tori orbiting Kehagias–Sfetsos naked singularities

et al. 2015

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“…It resembles the eigenfrequency modes that were proposed as a model for quasiperiodic oscillations in some X-ray binaries Montero & Zanotti 2012). A similar accretion history is found also for higher spin values, i.e., closer to extreme rotation, although we always assumed |a| < 1 (we did not consider the possibility of a naked singularity, but see Stuchlík et al 2011, for a recent discussion of such a possibility). Figure 4 shows levels of mass density at different time moments.…”

Section: Time Evolution Of Perturbed Configurationsupporting

confidence: 63%

Effect of the toroidal magnetic field on the runaway instability of relativistic tori

Hamerský

Karas

2013

A&A

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Aims. Runaway instability operates in fluid tori around black holes. It affects systems close to the critical (cusp overflowing) configuration. The runaway effect depends on the radial profile l(R) of the angular momentum distribution of the fluid, on the dimension-less spin a of the central black hole (|a| ≤ 1), and other factors, such as self-gravity. Previously it was demonstrated that for the power-law dependence of the radial angular momentum profile, l(R) ∝ R q , non-magnetized tori always become runaway stable for a sufficiently high positive value of q. Here we discuss the role of runaway instability within a framework of an axially symmetric model of perfect fluid endowed with a purely toroidal magnetic field. Methods. The gradual accretion of material over the cusp transfers the mass and angular momentum onto the black hole, thereby changing the intrinsic parameters of the Kerr metric. We studied the effect of the plasma parameter β (ratio of gas to magnetic pressure) and other parameters of the model on the evolution of critical configurations that are just on the verge of cusp overflow. Results. By contributing to the total pressure, the magnetic field causes small departures from the corresponding non-magnetic configuration in the early phases of accretion. However, we show that the toroidal magnetic component inside an accretion torus does not change the frequency of its oscillations significantly. We identify these oscillations as the radial epicyclic mode in our example. Nevertheless, these weak effects can trigger the runaway instability even in situations when the purely hydrodynamical regime of the torus is stable. On the other hand, in most cases the stable configuration remains unaffected, and the initial deviations gradually decay after several orbital periods. We show examples of the torus evolution depending on the initial magnetization β, the slope q, and the spin a. Conclusions. The toroidal magnetic field plays a more important role in the early phases of the accretion process until the perturbed configuration finds a new equilibrium or disappears because of the runaway instability.

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“…For a study of the Hawking radiation in Kerr and KerrNewman spacetimes see also [14]. [33][34][35][36][37][38][39][40][41][42]44,45]. Kerr naked singularities as particle accelerators are considered in [43] -see also [44,45].…”

Section: Introductionmentioning

confidence: 99%

Observers in Kerr spacetimes: the ergoregion on the equatorial plane

Pugliese

Quevedo

2018

Eur. Phys. J. C

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We perform a detailed analysis of the properties of stationary observers located on the equatorial plane of the ergosphere in a Kerr spacetime, including light-surfaces. This study highlights crucial differences between black hole and the super-spinner sources. In the case of Kerr naked singularities, the results allow us to distinguish between "weak" and "strong " singularities, corresponding to spin values close to or distant from the limiting case of extreme black holes, respectively. We derive important limiting angular frequencies for naked singularities. We especially study very weak singularities as resulting from the spin variation of black holes. We also explore the main properties of zero angular momentum observers for different classes of black hole and naked singularity spacetimes.

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Evolution of Kerr superspinars due to accretion counterrotating thin discs

Cited by 71 publications

References 81 publications

Perfect fluid tori orbiting Kehagias–Sfetsos naked singularities

Perfect fluid tori orbiting Kehagias–Sfetsos naked singularities

Effect of the toroidal magnetic field on the runaway instability of relativistic tori

Observers in Kerr spacetimes: the ergoregion on the equatorial plane

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