Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1

In this paper, we explore the photon region and the shadow of the rotating counterpart of a static charged Weyl black hole, which has been previously discussed according to null and time-like geodesics. The rotating black hole shows strong sensitivity to the electric charge and the spin parameter, and its shadow changes from being oblate to being sharp by increasing in the spin parameter. Comparing the calculated vertical angular diameter of the shadow with that of M87*, we found that the latter may possess about 1036 protons as its source of electric charge, if it is a rotating charged Weyl black hole. A complete derivation of the ergosphere and the static limit is also presented.

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Bound orbits around modified Hayward black holes

Modern Physics Letters A ◽

10.1142/s0217732321502370 ◽

2021 ◽

Author(s):

Bo Gao ◽

Xue-Mei Deng

Keyword(s):

Black Holes ◽

Black Hole ◽

Angular Momentum ◽

Gravitational Field ◽

Periodic Orbits ◽

Kerr Black Hole ◽

Periodic Oscillations ◽

Test Particles ◽

Spin Parameter ◽

Bound Orbits

The neutral time-like particle’s bound orbits around modified Hayward black holes have been investigated. We find that both in the marginally bound orbits (MBO) and the innermost stable circular orbits (ISCO), the test particle’s radius and its angular momentum are all more sensitive to one of the parameters [Formula: see text]. Especially, modified Hayward black holes with [Formula: see text] could mimic the same ISCO radius around the Kerr black hole with the spin parameter up to [Formula: see text]. Small [Formula: see text] could mimic the ISCO of small-spinning test particles around Schwarzschild black holes. Meanwhile, rational (periodic) orbits around modified Hayward black holes have also been studied. The epicyclic frequencies of the quasi-circular motion around modified Hayward black holes are calculated and discussed with respect to the observed Quasi-periodic oscillations (QPOs) frequencies. Our results show that rational orbits around modified Hayward black holes have different values of the energy from the ones of Schwarzschild black holes. The epicyclic frequencies in modified Hayward black holes have different frequencies from Schwarzschild and Kerr ones. These might provide hints for distinguishing modified Hayward black holes from Schwarzschild and Kerr ones by using the dynamics of time-like particles around the strong gravitational field.

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Particle motion around generic black holes coupled to non-linear electrodynamics

The European Physical Journal C ◽

10.1140/epjc/s10052-019-7286-2 ◽

2019 ◽

Vol 79 (9) ◽

Cited By ~ 5

Author(s):

Jaroslav Vrba ◽

Ahmadjon Abdujabbarov ◽

Arman Tursunov ◽

Bobomurat Ahmedov ◽

Zdeněk Stuchlík

Keyword(s):

Black Hole ◽

Energy Conditions ◽

Test Particles ◽

Stable Circular Orbit ◽

Spin Parameter ◽

Non Linear ◽

Innermost Stable Circular Orbit ◽

Charge Parameter ◽

Upper Estimate ◽

Black Hole Solutions

Abstract We study spherically symmetric magnetically charged generic black hole solutions of general relativity coupled to non-linear electrodynamics (NED). For characteristic values of the generic spacetime parameters we give the position of horizons in dependence on the charge parameter, demonstrating separation of the black hole and no-horizon solutions, and possibility of existence of solutions containing three horizons. We show that null, weak and strong energy conditions are violated when the outer horizon is approaching the center. We study effective potentials for photons and massive test particles and location of circular photon orbits (CPO) and innermost stable circular orbit (ISCO). We show that the unstable photon orbit can become stable, leading to the possibility of photon capture which affects on silhouette of the central object. The position of ISCO approaches the horizon with increasing charge parameter q and the energy at ISCO decreases with increasing charge parameter. We investigate this phenomenon and summarize for a variety of the generic spacetime parameters the upper estimate on the spin parameter of the Kerr black which can be mimicked by the generic charged black hole solutions.

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ERRATUM: “PRECISE MEASUREMENT OF THE SPIN PARAMETER OF THE STELLAR-MASS BLACK HOLE M33 X-7” (2008, ApJ, 679, L37)

The Astrophysical Journal ◽

10.1088/2041-8205/719/1/l109 ◽

2010 ◽

Vol 719 (1) ◽

pp. L109-L109 ◽

Cited By ~ 23

Author(s):

Jifeng Liu ◽

Jeffrey E. McClintock ◽

Ramesh Narayan ◽

Shane W. Davis ◽

Jerome A. Orosz

Keyword(s):

Black Hole ◽

Precise Measurement ◽

Stellar Mass ◽

Spin Parameter

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Optical properties of Kerr–Newman spacetime in the presence of plasma

The European Physical Journal C ◽

10.1140/epjc/s10052-020-8346-3 ◽

2020 ◽

Vol 80 (8) ◽

Cited By ~ 1

Author(s):

Gulmina Zaman Babar ◽

Abdullah Zaman Babar ◽

Farruh Atamurotov

Keyword(s):

Black Hole ◽

Kerr Black Hole ◽

Field Approximation ◽

Weak Field ◽

Jacobi Method ◽

Plasma Parameters ◽

Spin Parameter ◽

Newman Black Hole ◽

Shadow Cast ◽

Thermal Radiations

Abstract We have studied the null geodesics in the background of the Kerr–Newman black hole veiled by a plasma medium using the Hamilton–Jacobi method. The influence of black hole’s charge and plasma parameters on the effective potential and the generic photon orbits has been investigated. Furthermore, our discussion embodies the effects of black hole’s charge, plasma and the inclination angle on the shadow cast by the gravity with and without the spin parameter. We examined the energy released from the black hole as a result of the thermal radiations, which exclusively depends on the size of the shadow. The angle of deflection of the massless particles is also explored considering a weak-field approximation. We present our results in juxtaposition to the analogous black holes in General Relativity, particularly the Schwarzschild and Kerr black hole.

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Confirming the spin parameter of the black hole in Cygnus X-1 using the Insight-HXMT

Journal of High Energy Astrophysics ◽

10.1016/j.jheap.2020.03.001 ◽

2020 ◽

Vol 27 ◽

pp. 53-63 ◽

Cited By ~ 1

Author(s):

Xue-Shan Zhao ◽

Yan-Ting Dong ◽

Li-Jun Gou ◽

Ye Feng ◽

Nan Jia ◽

...

Keyword(s):

Black Hole ◽

Spin Parameter

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Shadow of a disformal Kerr black hole in quadratic degenerate higher-order scalar–tensor theories

The European Physical Journal C ◽

10.1140/epjc/s10052-020-08744-8 ◽

2020 ◽

Vol 80 (12) ◽

Author(s):

Fen Long ◽

Songbai Chen ◽

Mingzhi Wang ◽

Jiliang Jing

Keyword(s):

Black Hole ◽

Deformation Parameter ◽

Kerr Black Hole ◽

Arbitrary Spin ◽

Higher Order ◽

Fractal Structures ◽

Extreme Black Hole ◽

Spin Parameter ◽

Result Show ◽

Self Similar

AbstractWe have studied the shadow of a disformal Kerr black hole with an extra deformation parameter, which belongs to non-stealth rotating solutions in quadratic degenerate higher-order scalar–tensor (DHOST) theory. Our result show that the size of the shadow increases with the deformation parameter for the black hole with arbitrary spin parameter. However, the effect of the deformation parameter on the shadow shape depends heavily on the spin parameter of black hole and the sign of the deformation parameter. The change of the shadow shape becomes more distinct for the black hole with the more quickly rotation and the more negative deformation parameter. Especially, for the near-extreme black hole with negative deformation parameter, there exist a “pedicel”-like structure appeared in the shadow, which increases with the absolute value of deformation parameter. The eyebrow-like shadow and the self-similar fractal structures also appear in the shadow for the disformal Kerr black hole in DHOST theory. These features in the black hole shadow originating from the scalar field could help us to understand the non-stealth disformal Kerr black hole and quadratic DHOST theory.

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Shadow of a Kerr-like black hole

Proceedings of the International Astronomical Union ◽

10.1017/s174392131500770x ◽

2014 ◽

Vol 10 (S312) ◽

pp. 135-136

Author(s):

Farruh Atamurotov

Keyword(s):

Black Hole ◽

Angular Momentum ◽

Deformation Parameter ◽

Space Time ◽

Black Hole Spin ◽

Spin Parameter ◽

Kerr Space ◽

The One

AbstractThe shadow of a Kerr-like black hole has been considered and it was shown that in addition to the specific angular momentum a, deformation parameter of Kerr-like space-time essentially deforms the shape of the black hole shadow. For a given value of the black hole spin parameter a, the presence of a deformation parameter ε reduces the shadow and enlarges its deformation with respect to the one in the Kerr space-time.

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Possible imprints of cosmic strings in the shadows of galactic black holes

International Journal of Modern Physics D ◽

10.1142/s0218271814500606 ◽

2014 ◽

Vol 23 (07) ◽

pp. 1450060 ◽

Cited By ~ 22

Author(s):

Vassil K. Tinchev ◽

Stoytcho S. Yazadjiev

Keyword(s):

Black Holes ◽

Black Hole ◽

Cosmic String ◽

Cosmic Strings ◽

Kerr Black Hole ◽

Black Hole Spin ◽

Deficit Angle ◽

Spin Parameter ◽

Shadow Cast

We examine the shadow cast by a Kerr black hole pierced by a cosmic string. The observable images depend not only on the black hole spin parameter and the angle of inclination, but also on the deficit angle yielded by the cosmic string. The dependence of the observable characteristics of the shadow on the deficit angle is explored. The imprints in the black hole shadow left by the presence of a cosmic string can serve in principle as a method for observational detection of such strings.

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Observing the contour profile of a Kerr–Sen black hole

Modern Physics Letters A ◽

10.1142/s0217732318500992 ◽

2018 ◽

Vol 33 (17) ◽

pp. 1850099 ◽

Cited By ~ 5

Author(s):

X. G. Lan ◽

J. Pu

Keyword(s):

Black Hole ◽

Angular Momentum ◽

Naked Singularity ◽

Extremal Case ◽

Distortion Parameter ◽

Rotating Black Hole ◽

Dark Zone ◽

Spin Parameter ◽

The Mean ◽

In The Beginning

In this paper, the shadow and the corresponding naked singularity cast by a Kerr–Sen black hole are studied. It is found that the shadow of a rotating black hole would be a dark zone surrounded by a deformed circle, and the shadow is distorted more away from a circle when the black hole approaches the extremal case. Besides, it is shown that the mean radius of the shadow decreases and distortion parameter increases with the increasing of charge, respectively. However, the mean radius and the distortion parameter vary complicatedly with the change of spin parameter. In the beginning, both observables decrease rapidly with the increasing of specific angular momentum, nevertheless, they increase slightly in the latter part. These results show that there would be a significant effect of the spin on the shadows, which would be of great importance for probing the nature of the black hole.

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