scholarly journals 11.9. Jets from time-dependent accretion flows onto a black hole

1998 ◽  
Vol 184 ◽  
pp. 473-474
Author(s):  
Koji Nobuta ◽  
Tomoyuki Hanawa
Keyword(s):  
Black Hole ◽  
Numerical Simulations ◽  
Time Dependent ◽  
Accretion Flows ◽  
Γ Rays ◽  
Γ Ray

It is widely believed that accretion onto a black hole is the origin of X- and γ-ray emission and jets emerging from AGNs. Since the X- and γ-rays are highly variable, the accretion is also expected to be variable. We investigate highly variable hydrodynamical accretion with numerical simulations.

scholarly journals OBSERVATIONS OF MICROQUASAR CANDIDATES WITH THE MAGIC TELESCOPE

2008 ◽  
Vol 17 (10) ◽  
pp. 1859-1866
Author(s):  
◽  
J. RICO
Keyword(s):  
Black Hole ◽  
Experimental Evidence ◽  
Energy Band ◽  
High Energy ◽  
Time Dependent ◽  
X Ray ◽  
Orbital Cycles ◽  
Very High Energy ◽  
Γ Ray ◽  
Very High

We report on the results from the observations in very high energy band (VHE, Eγ ≥ 100 GeV ) of the γ-ray binary LS I +61 303 and the black hole X-ray binary (BHXB) Cygnus X-1. LS I +61 303 was recently discovered at VHE by MAGIC1 and here we present the preliminary results from an extensive observation campaign, comprising 112 observation hours covering 4 orbital cycles, aiming at determining the time-dependent features of the VHE emission. Cygnus X-1 was observed for a total of 40 hours during 26 nights, spanning the period between June and November 2006. We report on the results of the searches for steady and variable γ-ray signals from Cygnus X-1, including the first experimental evidence for an intense flare, of duration between 1.5 and 24 hours.

scholarly journals Numerical simulations of super-critical black hole accretion flows in general relativity

2014 ◽  
Vol 439 (1) ◽  
pp. 503-520 ◽  
Author(s):  
Aleksander Sądowski ◽  
Ramesh Narayan ◽  
Jonathan C. McKinney ◽  
Alexander Tchekhovskoy
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Numerical Simulations ◽  
Accretion Flows ◽  
Black Hole Accretion ◽  
Hole Accretion

scholarly journals VERY-HIGH ENERGY PROCESSES IN BLACK HOLE MAGNETOSPHERE: THE CASE OF M87

2014 ◽  
Vol 28 ◽  
pp. 1460189 ◽  
Author(s):  
STEPHANE VINCENT
Keyword(s):  
Black Hole ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Morphological Studies ◽  
Very High Energy ◽  
Γ Rays ◽  
Γ Ray ◽  
Energy Processes ◽  
Very High

M87 is a nearby radio galaxy that is detected at energies ranging from radio to very high energy (VHE) γ-rays. Its proximity and its jet, misaligned from our line of sight, enable detailed morphological studies. The detection of rapidly variable TeV emissions on timescale of ~ 1 day implies a source of a few Schwarzschild radii R Sch . The γ-ray telescopes cannot provide images with a sufficient resolution to localize the sites of the γ-ray production. However, both X-ray and radio observations have shown evidence that charged particles are accelerated in the immediate vicinity of the black hole closer than 100 R Sch . We propose that the non-thermal particle acceleration and the VHE emission processes may occur in a pair-starved region of the black hole (BH) magnetosphere. We produce a broadband spectral energy distribution (SED) of the resulting radiation and compare the model with the observed fluxes from the nucleus of M87 for the high γ-ray activities.

scholarly journals Nuclear γ-ray emission from very hot accretion flows

2019 ◽  
Vol 623 ◽  
pp. A174
Author(s):  
E. Kafexhiu ◽  
F. Aharonian ◽  
M. Barkov
Keyword(s):  
Black Hole ◽  
Chemical Composition ◽  
Nuclear Reactions ◽  
High Energy ◽  
Stable Orbit ◽  
Accretion Flow ◽  
Accretion Flows ◽  
Solar Composition ◽  
Γ Ray ◽  
Radial Evolution

Optically thin accretion plasmas can reach ion temperatures Ti ≥ 1010 K and thus trigger nuclear reactions. Using a large nuclear interactions network, we studied the radial evolution of the chemical composition of the accretion flow toward the black hole and computed the emissivity in nuclear γ-ray lines. In the advection dominated accretion flow (ADAF) regime, CNO and heavier nuclei are destroyed before reaching the last stable orbit. The overall luminosity in the de-excitation lines for a solar composition of plasma can be as high as few times 10−5 the accretion luminosity (Ṁc2) and can be increased for heavier compositions up to 10−3. The efficiency of transformation of the kinetic energy of the outflow into high energy (≥100 MeV) γ-rays through the production and decay of π0-mesons can be higher, up to 10−2 of the accretion luminosity. We show that in the ADAF model up to 15% of the mass of accretion matter can “evaporate” in the form of neutrons.

scholarly journals Jets from Time‐dependent Accretion Flows onto a Black Hole

1999 ◽  
Vol 510 (2) ◽  
pp. 614-630 ◽  
Author(s):  
Koji Nobuta ◽  
Tomoyuki Hanawa
Keyword(s):  
Black Hole ◽  
Time Dependent ◽  
Accretion Flows

scholarly journals Simulations of disks in binary systems using parallelized SPH to reach extreme spatial resolution

2003 ◽  
Vol 208 ◽  
pp. 427-428
Author(s):  
D. Molteni ◽  
F. Fauci ◽  
G. Gerardi ◽  
M. A. Valenza
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Numerical Simulations ◽  
Spatial Resolution ◽  
Spectral Properties ◽  
Binary Systems ◽  
Compact Star ◽  
Close Binary ◽  
Gas Transfer ◽  
Set Up

Results of 3D numerical simulations of the gas transfer in close binary systems show that it is possible the production of accretion streams having low specific angular momentum in a region close to the accreting star. These streams are mainly placed above the orbital disc. The eventual formation of such bulges and shock heated flows is interesting in the context of advection dominated solutions and for the explanation of spectral properties of the Black Hole candidates in binary systems. We set up a parallelized version of 3D S.P.H. code, using domain decomposion. with increasing spatial resolution around the compact star.

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