scholarly journals Gravitational effect of plasma particles on the shadow of Schwarzschild black holes

2022 ◽  
Vol 82 (1) ◽  
Author(s):  
Qiang Li ◽  
Yanni Zhu ◽  
Towe Wang
Keyword(s):  
Black Holes ◽  
Active Galactic Nuclei ◽  
Hydrogen Plasma ◽  
Galactic Nuclei ◽  
Gravitational Effect ◽  
Plasma Medium ◽  
Schwarzschild Black Hole ◽  
Refractive Correction ◽  
Intensity Map ◽  
Independent Parameters

AbstractConsidering a Schwarzschild black hole surrounded by a fully ionized hydrogen plasma, we study the effect of the gravitational field of the plasma particles on the shadow. We take a formalism in which this effect is unified with the refractive effect of the plasma medium studied previously, but the two effects are characterized by two independent parameters. For semi-realistic values of parameters, we find their corrections to the shadow radius are both negligible, and the gravitational correction can overtake the refractive correction for active galactic nuclei of masses larger than $$10^9M_{\odot }$$ 10 9 M ⊙ . With unrealistically large values of parameters, we illustrate the two effects on the light trajectories and the intensity map.

scholarly journals Epicyclic Oscillations around Simpson–Visser Regular Black Holes and Wormholes

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 279
Author(s):  
Zdeněk Stuchlík ◽  
Jaroslav Vrba
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Observational Data ◽  
High Frequency ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Periodic Oscillations ◽  
High Length ◽  
Circular Geodesic

We study epicyclic oscillatory motion along circular geodesics of the Simpson–Visser meta-geometry describing in a unique way regular black-bounce black holes and reflection-symmetric wormholes by using a length parameter l. We give the frequencies of the orbital and epicyclic motion in a Keplerian disc with inner edge at the innermost circular geodesic located above the black hole outer horizon or on the our side of the wormhole. We use these frequencies in the epicyclic resonance version of the so-called geodesic models of high-frequency quasi-periodic oscillations (HF QPOs) observed in microquasars and around supermassive black holes in active galactic nuclei to test the ability of this meta-geometry to improve the fitting of HF QPOs observational data from the surrounding of supermassive black holes. We demonstrate that this is really possible for wormholes with sufficiently high length parameter l.

scholarly journals Planck Neutrinos as Ultra High Energy Cosmic Rays

2020 ◽  
Vol 29 (1) ◽  
pp. 40-46
Author(s):  
Dmitri L. Khokhlov
Keyword(s):  
Black Holes ◽  
Cosmic Rays ◽  
Standard Model ◽  
Active Galactic Nuclei ◽  
Planck Scale ◽  
Galactic Nuclei ◽  
High Energy ◽  
Ultra High Energy ◽  
High Energy Cosmic Rays ◽  
The Standard Model

AbstractThe studied conjecture is that ultra high energy cosmic rays (UHECRs) are hypothetical Planck neutrinos arising in the decay of the protons falling onto the gravastar. The proton is assumed to decay at the Planck scale into positron and four Planck neutrinos. The supermassive black holes inside active galactic nuclei, while interpreted as gravastars, are considered as UHECR sources. The scattering of the Planck neutrinos by the proton at the Planck scale is considered. The Planck neutrinos contribution to the CR events may explain the CR spectrum from 5 × 1018 eV to 1020 eV. The muon number in the Planck neutrinos-initiated shower is estimated to be larger by a factor of 3/2 in comparison with the standard model that is consistent with the observational data.

scholarly journals Intensity ratios for XDR/PDR identification

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
C.-E. Green ◽  
M. R. Cunningham ◽  
J. A. Green ◽  
J. R. Dawson ◽  
P. A. Jones ◽  
...  
Keyword(s):  
Black Holes ◽  
Star Formation ◽  
Active Galactic Nuclei ◽  
Intensity Ratio ◽  
Galactic Nuclei ◽  
Relative Influence ◽  
Calculation Methods ◽  
X Ray ◽  
Ratio Calculation ◽  
Intensity Ratios

AbstractThe intensity ratios of HCO+/HCN and HNC/HCN (1-0) reveal the relative influence of star formation and active galactic nuclei (AGN) or black holes on the circum-nuclear gas of a galaxy, allowing the identification of X-ray dominated regions (XDRs) and Photon-dominated regions (PDRs). It is not always clear in the literature how this intensity ratio calculation has been, or should be performed. This paper discusses ratio calculation methods for interferometric data.

scholarly journals Symmetry and the Arrow of Time in Theoretical Black Hole Astrophysics

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
David Garofalo
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Time Reversal ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Arrow Of Time ◽  
Time Symmetry ◽  
The Universe

While the basic laws of physics seem time-reversal invariant, our understanding of the apparent irreversibility of the macroscopic world is well grounded in the notion of entropy. Because astrophysics deals with the largest structures in the Universe, one expects evidence there for the most pronounced entropic arrow of time. However, in recent theoretical astrophysics work it appears possible to identify constructs with time-reversal symmetry, which is puzzling in the large-scale realm especially because it involves the engines of powerful outflows in active galactic nuclei which deal with macroscopic constituents such as accretion disks, magnetic fields, and black holes. Nonetheless, the underlying theoretical structure from which this accreting black hole framework emerges displays a time-symmetric harmonic behavior, a feature reminiscent of basic and simple laws of physics. While we may expect such behavior for classical black holes due to their simplicity, manifestations of such symmetry on the scale of galaxies, instead, surprise. In fact, we identify a parallel between the astrophysical tug-of-war between accretion disks and jets in this model and the time symmetry-breaking of a simple overdamped harmonic oscillator. The validity of these theoretical ideas in combination with this unexpected parallel suggests that black holes are more influential in astrophysics than currently recognized and that black hole astrophysics is a more fundamental discipline.

Polarimetric differences between Schwarzschild and Kerr black holes in active galactic nuclei

2011 ◽  
Vol 55 (8) ◽  
pp. 683-688 ◽  
Author(s):  
N. A. Silant’ev ◽  
M. Yu. Piotrovich ◽  
Yu. N. Gnedin ◽  
T. M. Natsvlishvili
Keyword(s):  
Black Holes ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Kerr Black Holes

scholarly journals Supermassive black holes surrounded by dark matter modeled as anisotropic fluid: epicyclic oscillations and their fitting to observed QPOs

2021 ◽  
Vol 2021 (11) ◽  
pp. 059
Author(s):  
Z. Stuchlík ◽  
J. Vrba
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Black Hole Spacetimes ◽  
Test Particles

Abstract Recently introduced exact solution of the Einstein gravity coupled minimally to an anisotropic fluid representing dark matter can well represent supermassive black holes in galactic nuclei with realistic distribution of dark matter around the black hole, given by the Hernquist-like density distribution. For these fluid-hairy black hole spacetimes, properties of the gravitational radiation, quasinormal ringing, and optical phenomena were studied, giving interesting results. Here, using the range of physical parameters of these spacetimes allowing for their relevance in astrophysics, we study the epicyclic oscillatory motion of test particles in these spacetimes. The frequencies of the orbital and epicyclic motion are applied in the epicyclic resonance variant of the geodesic model of quasiperiodic oscillations (QPOs) observed in active galactic nuclei to demonstrate the possibility to solve the cases where the standard vacuum black hole spacetimes are not allowing for explanation of the observed data. We demonstrate that the geodesic model can explain the QPOs observed in most of the active galactic nuclei for the fluid-hairy black holes with reasonable halo parameters.

Dependence of the Spin of Supermassive Black Holes on the Eddington Factor for Accretion Disks in Active Galactic Nuclei

Astrophysics ◽  
2016 ◽  
Vol 59 (4) ◽  
pp. 439-448 ◽  
Author(s):  
M. Yu. Piotrovich ◽  
S. D. Buliga ◽  
Yu. N. Gnedin ◽  
A. G. Mikhailov ◽  
T. M. Natsvlishvili
Keyword(s):  
Black Holes ◽  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Galactic Nuclei ◽  
Supermassive Black Holes
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