scholarly journals General relativistic model for the gravitational field of active galactic nuclei surrounded by a disk

2005 ◽  
Vol 71 (4) ◽  
Author(s):  
D. Vogt ◽  
P. S. Letelier
1998 ◽  
Vol 188 ◽  
pp. 455-456
Author(s):  
M. Yokosawa

Active galactic nuclei(AGN) produce many type of active phenomena, powerful X-ray emission, UV hump, narrow beam ejection, gamma-ray emission. Energy of these phenomena is thought to be brought out binding energy between a black hole and surrounding matter. What condition around a black hole produces many type of active phenomena? We investigated dynamical evolution of accretion flow onto a black hole by using a general-relativistic, hydrodynamic code which contains a viscosity based on the alpha-model. We find three types of flow's pattern, depending on thickness of accretion disk. In a case of the thin disk with a thickness less than the radius of the event horizon at the vicinity of a marginally stable orbit, the accreting flow through a surface of the marginally stable orbit becomes thinner due to additional cooling caused by a general-relativistic Roche-lobe overflow and horizontal advection of heat. An accretion disk with a middle thickness, 2rh≤h≤ 3rh, divides into two flows: the upper region of the accreting flow expands into the atmosphere of the black hole, and the inner region of the flow becomes thinner, smoothly accreting onto the black hole. The expansion of the flow generates a dynamically violent structure around the event horizon. The kinetic energy of the violent motion becomes equivalent to the thermal energy of the accreting disk. The shock heating due to violent motion produces a thermally driven wind which flows through the atmosphere above the accretion disk. A very thick disk, 4rh≤h,forms a narrow beam whose energy is largely supplied from hot region generated by shock wave. The accretion flowing through the thick disk,h≥ 2rh, cannot only form a single, laminar flow falling into the black hole, but also produces turbulent-like structure above the event horizon. The middle disk may possibly emit the X-ray radiation observed in active galactic nuclei. The thin disk may produce UV hump of Seyfert galaxy. Thick disk may produce a jet observed in radio galaxy. The thickness of the disk is determined by accretion rate, such ashκ κes/cṁf(r) κ 10rhṁf(r), at the inner region of the disk where the radiation pressure dominates over the gas pressure. Here, Ṁ is the accretion rate and ṁ is the normarized one by the critical-mass flux of the Eddington limit. κesandcare the opacity by electron scattering and the velocity of light.f(r) is a function with a value of unity far from the hole.


2011 ◽  
Vol 417 (1) ◽  
pp. 178-183 ◽  
Author(s):  
G. Risaliti ◽  
E. Nardini ◽  
M. Elvis ◽  
L. Brenneman ◽  
M. Salvati

1997 ◽  
Vol 163 ◽  
pp. 667-671
Author(s):  
Shinji Koide ◽  
Kazunari Shibata ◽  
Takahiro Kudoh

AbstractRecently, superluminal motions are observed not only from active galactic nuclei but also in our Galaxy. These phenomena are explained as relativistic jets propagating almost toward us with Lorentz factor more than 2. For the formation of such a relativistic jet, magnetically driven mechanism around a black hole is most promising. We have extended the 2.5D Newtonian MHD jet model (Shibata & Uchida 1986) to general relativistic regime. For this purpose, we have developed a general relativistic magnetohydrodynamic (GRMHD) numerical code and applied it to the simulation of the magnetized accretion disk around a black hole. We have found the formation of magnetically driven jets with 86 percent of light velocity (i.e. Lorentz factor ~ 2.0).


2006 ◽  
Vol 2 (S238) ◽  
pp. 425-426
Author(s):  
Tomáš Pecháček ◽  
Michal Dovčiak ◽  
Vladimír Karas

AbstractSome aspects of power-spectral densities (PSD) of active galactic nuclei are similar to those of galactic black hole X-ray binary systems (McHardy et al. 2005). The signal originates near a black hole and its modulation by general-relativistic effects should be taken into account (Życki & Nedźwiecki 2005). We modified the previous calculations of these effects, assuming a model of spots which occur on the disc surface and decay with a certain lifetime.


2006 ◽  
pp. 49-55
Author(s):  
A.L. Poplavsky ◽  
O.P. Kuznechik ◽  
N.I. Stetyukevich

In this paper one presents an analytical model of accretion disk magnetosphere dynamics around supermassive nonrotating black holes in the centers of active galactic nuclei. Based on general relativistic equations of magneto hydrodynamics, the nonstationary solutions for time-dependent dynamo action in the accretion disks, spatial and temporal distribution of magnetic field are found. It is shown that there are two distinct stages of dynamo process: the transient and the steady-state regimes, the induction of magnetic field at t > 6:6665 x 1011GM/c3 s becomes stationary, magnetic field is located near the innermost stable circular orbit, and its value rises up to ~ 105 G. Applications of such systems with nonrotating black holes in real active galactic nuclei are discussed.


2022 ◽  
Vol 924 (1) ◽  
pp. 28
Author(s):  
Shota Kisaka ◽  
Amir Levinson ◽  
Kenji Toma ◽  
Idan Niv

Abstract We study the response of a starved Kerr black hole magnetosphere to abrupt changes in the intensity of disk emission and in the global magnetospheric current, by means of one-dimensional general relativistic particle-in-cell simulations. Such changes likely arise from the intermittency of the accretion process. We find that in cases where the pair-production opacity contributed by the soft disk photons is modest, as in, e.g., M87, such changes can give rise to delayed, strong teraelectronvolt (TeV) flares, dominated by curvature emission of particles accelerated in the gap. The flare rise time, and the delay between the external variation and the onset of the flare emitted from the outer gap boundary, are of the order of the light-crossing time of the gap. The rapid, large-amplitude TeV flares observed in M87, and perhaps, other active galactic nuclei may be produced by such a mechanism.


2004 ◽  
Vol 607 (1) ◽  
pp. 580-595 ◽  
Author(s):  
F. de Felice ◽  
M. T. Crosta ◽  
A. Vecchiato ◽  
M. G. Lattanzi ◽  
B. Bucciarelli

1999 ◽  
pp. 17-29
Author(s):  
L.C. Popovic

The gravitational field effect on atomic data for H and C IV transitions are considered as a perturbation of initial and final energy levels. We found that this perturbation increases with the principal quantum number. Here we give several expressions for estimation of this effect and its influence on atomic data parameters. Also, the calculations of atomic data for 1s ? 2p (Ly?) and 2s ? 3p transitions of hydrogen atom as well as atomic data for 2s2S1/2?2p2P0 1/2,3/2 transitions of C IV (1UV) as a function of deformation of energy levels due to gravitation field and gravitational redshift are given. The gravitational field effect should be estimated and should be taken into account in calculation of atomic data for emitters in Broad Line Regions (BLRs) of Active Galactic Nuclei (AGN).


Sign in / Sign up

Export Citation Format

Share Document