Circular motion and energy extraction in a rotating black hole

Shahzadi, Misbah; Yousaf, Z.; Khan, Saeed Ullah

doi:10.1016/j.dark.2019.100263

Cited by 18 publications

(8 citation statements)

References 39 publications

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“…Henceforth, studying a BH's shadow will be a fruitful way for a better understanding of astrophysical BHs, as well as for the comparison of general relativity to those of modern theories [29]. To have information on BHs, the approaches of null geodesics and gravitational lensing are of compelling interest [30,31,32]. Recently, scientists have finally succeeded in obtaining the first-ever image of a supermassive BH, at the centre of the M87 galaxy [33,34,35].…”

Section: Introductionmentioning

confidence: 99%

Shadow cast by a rotating charged black hole in quintessential dark energy

Khan,

Ren

2020

Preprint

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The existence of quintessential dark energy around a black hole has considerable consequences on its spacetime geometry. Hence, in this article, we explore its effect on horizons and the silhouette generated by a Kerr-Newman black hole in quintessential dark energy. Moreover, to analyse the deflection angle of light, we utilize the Gauss-Bonnet theorem. The obtained result demonstrates that, due to the dragging effect, the black hole spin elongates its shadow in the direction of the rotational axis, while increases the deflection angle. On the other hand, the black hole charge diminishing its shadow, as well as the angle of light's deflection. Besides, both spin and charge significantly increase the distortion effect in the black hole's shadow. The quintessence parameter γ, increases the shadow radius, while decreases the distortion effect at higher values of charge and spin parameters.

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Section: Introductionmentioning

confidence: 99%

Shadow cast by a rotating charged black hole in quintessential dark energy

Khan,

Ren

2020

Preprint

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“…For α 2 = 0 and a = 0, the Kerr-MOG BH reduces to the Kerr and Schwarzschild-MOG BH, respectively. For details, see [83,[85][86][87].…”

Section: Kerr-mog Bhsmentioning

confidence: 99%

Testing alternative theories of gravity by fitting the hot-spot data of Sgr A*

et al. 2022

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We are fitting dynamics of electrically neutral hot-spot orbiting around Sagittarius A* (Sgr A*) source in Galactic center, represented by various modifications of the standard Kerr black hole (BH), to the three flares observed by the GRAVITY instrument on May 27, July 22, July 28, 2018. We consider stationary, axisymmetric, and asymptotically flat spacetimes describing charged BHs in general relativity (GR) combined with nonlinear electrodynamics, or reflecting the influence of dark matter (DM), or in so called parameterized dirty Kerr spacetimes, and test them using the hot-spot data. We show that the orbital frequencies as well as positions of the hot-spots orbiting the considered BHs fit the observed positions and periods of the flare orbits, and give relevant constraints on the parameters of the considered BH spacetimes and the gravity or other theories behind such modified spacetimes.

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“…Negative energy states within ergosphere of a BH has essential consequences in BH physics. They could be occurred due to the counter-rotating orbits (as in Kerr BH), as well as due to the electromagnetic interaction (as in RN BH) [37]. Finding the energy limits of a particle is of considerable interest, which they have at a particular position.…”

Section: Negative Energy Statesmentioning

confidence: 99%

“…The evaluation of Penrose mechanism around a non-singular rotating BH, reveals that BH electric charge diminishing the efficiency of energy extraction [36]. While in the case of Kerr-MOG BH, it is the rotational parameter which enriches the efficiency of energy extraction [37]. Recently, Khan et al [38] studied the braneworld Kerr BH and concluded that both spin and brane parameter of the BH, contributes to the efficiency of Penrose mechanism.…”

Section: Introductionmentioning

confidence: 99%

Particle dynamics around a dyonic charged black hole

Khan,

Ren

2020

Preprint

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In this article, we study the circular motion of particles and the well-known Penrose mechanism around a Kerr-Newman-Kasuya black hole spacetime. The inner and outer horizons, as well as ergosurfaces of the said black hole, are briefly examined under the effect of spin and dyonic charge. Moreover, by limiting our exploration to the equatorial plane, we discuss the characteristics of circular geodesics and investigate both photons, as well as marginally stable circular orbits. It is noted that black hole charge diminishing the radii of photon and marginally stable circular orbits. To investigate the nature of particle dynamics, we studied the effective potential and Lyapunov exponent. While inspecting the process of energy extraction, we derived the Wald inequality, which can help us to locate the energy limits of the Penrose process. Furthermore, we have found expressions for the negative energy states and the efficiency of energy extraction. The obtained result illustrates that both black hole rotation and dyonic charge contributes to the efficiency of energy extraction.

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Circular motion and energy extraction in a rotating black hole

Cited by 18 publications

References 39 publications

Shadow cast by a rotating charged black hole in quintessential dark energy

Shadow cast by a rotating charged black hole in quintessential dark energy

Testing alternative theories of gravity by fitting the hot-spot data of Sgr A*

Particle dynamics around a dyonic charged black hole

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