scholarly journals EFFECTS OF HIGH-ENERGY PARTICLES ON ACCRETION FLOWS ONTO A SUPERMASSIVE BLACK HOLE

2014 ◽  
Vol 791 (2) ◽  
pp. 100 ◽  
Author(s):  
Shigeo S. Kimura ◽  
Kenji Toma ◽  
Fumio Takahara
Keyword(s):  
Black Hole ◽  
High Energy ◽  
Accretion Flows ◽  
Supermassive Black Hole ◽  
High Energy Particles

OBSERVATIONAL CONSTRAINTS ON STRONG GRAVITY

2011 ◽  
Vol 20 (14) ◽  
pp. 2755-2760
Author(s):  
CHRIS DONE
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Strong Field ◽  
Field Tests ◽  
High Energy ◽  
Observational Constraints ◽  
Tests Of General Relativity ◽  
Strong Gravity ◽  
Accretion Flows ◽  
Spacetime Curvature

Accretion onto a black hole transforms the darkest objects in the universe to the brightest. The high energy radiation emitted from the accretion flow before it disappears forever below the event horizon lights up the regions of strong spacetime curvature close to the black hole, enabling strong field tests of General Relativity. I review the observational constraints on strong gravity from such accretion flows, and show how the data strongly support the existence of such fundamental General Relativistic features of a last stable orbit and the event horizon. However, these successes also imply that gravity does not differ significantly from Einstein's predictions above the event horizon, so any new theory of quantum gravity will be very difficult to test.

scholarly journals Acceleration and escape processes of high-energy particles in turbulence inside hot accretion flows

2019 ◽  
Vol 485 (1) ◽  
pp. 163-178 ◽  
Author(s):  
Shigeo S Kimura ◽  
Kengo Tomida ◽  
Kohta Murase
Keyword(s):  
Dominant Role ◽  
High Energy ◽  
Field Configuration ◽  
Particle Energy ◽  
Acceleration Process ◽  
Accretion Flows ◽  
Bulk Motion ◽  
Normal Diffusion ◽  
Magnetohydrodynamic Simulations ◽  
High Energy Particles

Abstract We investigate acceleration and propagation processes of high-energy particles inside hot accretion flows. The magnetorotational instability (MRI) creates turbulence inside accretion flows, which triggers magnetic reconnection and may produce non-thermal particles. They can be further accelerated stochastically by the turbulence. To probe the properties of such relativistic particles, we perform magnetohydrodynamic simulations to obtain the turbulent fields generated by the MRI, and calculate orbits of the high-energy particles using snapshot data of the MRI turbulence. We find that the particle acceleration is described by a diffusion phenomenon in energy space with a diffusion coefficient of the hard-sphere type: Dε ∝ ε2, where ε is the particle energy. Eddies in the largest scale of the turbulence play a dominant role in the acceleration process. On the other hand, the stochastic behaviour in configuration space is not usual diffusion but superdiffusion: the radial displacement increases with time faster than that in the normal diffusion. Also, the magnetic field configuration in the hot accretion flow creates outward bulk motion of high-energy particles. This bulk motion is more effective than the diffusive motion for higher energy particles. Our results imply that typical active galactic nuclei that host hot accretion flows can accelerate CRs up to ε ∼ 0.1−10 PeV.

scholarly journals Acceleration of particles up to PeV energies at the galactic centre

2016 ◽  
Vol 12 (S324) ◽  
pp. 317-321
Author(s):  
Stefano Gabici ◽  
Felix A. Aharonian ◽  
Emmanuel Moulin ◽  
Aion Viana
Keyword(s):  
Black Hole ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Galactic Centre ◽  
Acceleration Of Particles ◽  
Supermassive Black Hole ◽  
Centre Region ◽  
Very High Energy ◽  
Sgr A ◽  
Very High

AbstractRecent very high energy observations of the galactic centre region performed by H.E.S.S. revealed the presence of a powerful PeVatron. This is the first of such objects detected, and its most plausible counterpart seems to be associated to Sgr A*, the supermassive black hole in the centre of our galaxy. The implications of this discovery will be discussed, in particular in the context of the problem of the origin of galactic cosmic rays.

scholarly journals Acceleration of ultra-high-energy cosmic rays by local supermassive black hole candidates

2021 ◽  
Author(s):  
Arman Tursunov ◽  
Arman Tursunov, ◽  
David Alvarez-Castillo, ◽  
Alok Gupta, ◽  
Bohdan Hnatyk, ◽  
...  
Keyword(s):  
Black Hole ◽  
Cosmic Rays ◽  
High Energy ◽  
Ultra High Energy ◽  
High Energy Cosmic Rays ◽  
Supermassive Black Hole ◽  
Black Hole Candidates

scholarly journals GRS 1915+105 “celebrates its majority” (1992–2010)

2010 ◽  
Vol 6 (S275) ◽  
pp. 270-274
Author(s):  
Alberto J. Castro-Tirado
Keyword(s):  
Black Hole ◽  
Radio Galaxies ◽  
High Energy ◽  
Accretion Disc ◽  
Γ Ray ◽  
High Energy Particles ◽  
Travel Distances ◽  
Open Issues

AbstractOver the 18 years since its discovery, GRS 1915+105 has continuously brightened in the X/γ-ray sky. It is considered the prototypical microquasar. Most of these are LMXBs that show sporadic ejection of matter at apparently superluminal velocities. In these the three basic ingredients of quasars are found: a black hole, an accretion disc and collimated jets of high energy particles, but in microquasars the black hole is only a few M⊙ instead of several × 106 M⊙; the accretion disc had mean thermal temperature of several × 106 K instead of several × 103 K, and the particles ejected at relativistic speeds travel distances of a few ly only, compared to few × 106 ly as in radio galaxies. However many open issues remain to be addressed.

scholarly journals Cosmic rays from the nearby starburst galaxy NGC 253: the effect of a low-luminosity active galactic nucleus

2020 ◽  
Vol 494 (2) ◽  
pp. 2109-2116 ◽  
Author(s):  
E M Gutiérrez ◽  
G E Romero ◽  
F L Vieyro
Keyword(s):  
Black Hole ◽  
Cosmic Ray ◽  
High Energy ◽  
Starburst Galaxy ◽  
Active Nucleus ◽  
Accretion Flow ◽  
Supermassive Black Hole ◽  
Cosmic Ray Acceleration ◽  
The Galaxy ◽  
Dynamo Mechanism

ABSTRACT NGC 253 is a nearby starburst galaxy in the Sculptor group located at a distance of ∼3.5 Mpc that has been suggested by some authors as a potential site for cosmic ray acceleration up to ultrahigh energies. Its nuclear region is heavily obscured by gas and dust, which prevents establishing whether or not the galaxy harbours a supermassive black hole coexisting with the starburst. Some sources have been proposed in the literature as candidates for an active nucleus. In this work, we aim at determining the implications that the presence of a supermassive black hole at the nucleus of NGC 253 might have on cosmic ray acceleration. With this aim, we model the accretion flow on to the putative active nucleus, and we evaluate the feasibility of particle acceleration by the black hole dynamo mechanism. As a by-product, we explore the potential contribution from non-thermal particles in the accretion flow to the high-energy emission of the galaxy. We found that in the three most plausible nucleus candidates, the emission of the accretion flow would inhibit the black hole dynamo mechanism. To rule out completely the influence that a putative nucleus in NGC 253 might have in cosmic ray acceleration, a better clarification concerning the true nature of the nucleus is needed.

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