Magnetic field strength at the innermost circular orbit in accretion disk of supermassive black hole in active galactic nuclei: comparison with the equipartition value

2015 ◽  
Vol 357 (2) ◽  
Author(s):  
M. Y. Piotrovich ◽  
S. D. Buliga ◽  
Y. N. Gnedin ◽  
T. M. Natsvlishvili ◽  
N. A. Silant’ev
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Field Strength ◽  
Active Galactic Nuclei ◽  
Magnetic Field Strength ◽  
Accretion Disk ◽  
Circular Orbit ◽  
Galactic Nuclei ◽  
Supermassive Black Hole

2.9. Microlens mapping of disks in active galactic nuclei

1998 ◽  
Vol 184 ◽  
pp. 75-76 ◽  
Author(s):  
A. Yonehara ◽  
S. Mineshige ◽  
J. Fukue ◽  
M. Umemura ◽  
E.L. Turner
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Central Region ◽  
Galactic Nuclei ◽  
Direct Information ◽  
Supermassive Black Hole ◽  
Disk Size

Generally, it is believed that there is a supermassive black hole and a surrounding accretion disk in a central region of active galactic nuclei (AGN). However, it is quite difficult to obtain direct information about the center of AGN, because the accretion disk size is far too small to resolve.

Determination of supermassive black hole spins in active galactic nuclei

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040054
Author(s):  
M. Yu. Piotrovich ◽  
V. L. Afanasiev ◽  
S. D. Buliga ◽  
T. M. Natsvlishvili
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Disk Model ◽  
Supermassive Black Hole

Based on spectropolarimetry for a number of active galactic nuclei in Seyfert 1 type galaxies observed with the 6-m BTA telescope, we have estimated the spins of the supermassive black holes at the centers of these galaxies. We have determined the spins based on the standard Shakura-Sunyaev accretion disk model. More than 70% of the investigated active galactic nuclei are shown to have Kerr supermassive black holes with a dimensionless spin greater than 0.9.

scholarly journals Determination of magnetic field strength on the event horizon of supermassive black holes in active galactic nuclei

2020 ◽  
Vol 495 (1) ◽  
pp. 614-620
Author(s):  
M Yu Piotrovich ◽  
A G Mikhailov ◽  
S D Buliga ◽  
T M Natsvlishvili
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Field Strength ◽  
Active Galactic Nuclei ◽  
Magnetic Field Strength ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Mean Values ◽  
The Magnetic Field

ABSTRACT We estimated the magnetic field strength at the event horizon for a sample of supermassive black holes (SMBHs) in active galactic nuclei (AGNs). Our estimates were made using the values of the inclination angles of the accretion disc to the line of sight, which we obtained previously from spectropolarimetric observations in the visible spectrum. We also used published values of full width at half-maximum of spectral line Hβ from broad-line region, masses of SMBHs, and luminosity of AGNs at 5100 $\mathring{\rm A}$. In addition, we used the literature data on the spins of SMBHs obtained from their X-ray spectra. Our estimates showed that the magnetic field strength at the event horizon of the majority of SMBHs in AGNs range from several to tens of kG and have mean values of about 104 G. At the same time, for individual objects, the fields are significantly larger – of the order of hundreds kG or even 1 MG.

scholarly journals Numerical Studies of Astrophysical Objects at Fesenkov Astrophysical Institute (FAI)

2018 ◽  
Vol 2 (1) ◽  
pp. 124-134
Author(s):  
Assylkhan Bibossinov ◽  
◽  
Denis Yurin ◽  
Chingis Omarov ◽  
◽  
...  
Keyword(s):  
Black Hole ◽  
Numerical Simulations ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Large Scale ◽  
International Workshop ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Numerical Studies ◽  
Astrophysical Objects

Numerical studies of astrophysical objects are a relatively new direction in Fesenkov Astrophysical Institute (FAI) and is mainly represented by the Laboratory of Cosmology, Stellar Dynamics and Computational Astrophysics. The lab seeks to understand the evolution of gravitating systems at various scales – from star clusters to galaxies to large-scale structure of the universe as a whole, and tackles these problems both through analytical methods and through numerical simulations. The particular focus is on numerical simulations of star clusters, especially those found in active galactic nuclei – this is a topic of oldestablished collaboration with colleagues from Astronomisches Rechen-Institut (Heidelberg) and National Astronomical Observatories of China (Beijing). The prominent example is STARDISK project dedicated to the numerical research of active galactic nuclei as multicomponent systems composed of compact stellar cluster, gaseous accretion disk and a supermassive black hole. It is demonstrated that an accretion disk can noticeably decelerate stars and thus enhance the accretion rate onto the black hole. In 2013 FAI hosted the MODEST-13 International Workshop dedicated to modeling of star clusters. Recently a new project has been approved aimed at construction of triaxial equilibrium N-body systems that can be of great help in various numerical experiments with disk galaxies. There are also long standing plans to perform cosmological simulations of large scale structures to test a new approach to dark matter and energy actively developed at FAI. For numerical calculations, FAI has a small, but growing computer cluster consisting of several high-performance computing servers equipped with computational GPU cards.

scholarly journals Dynamical Evolution of Accretion Flow onto a Black Hole

1998 ◽  
Vol 188 ◽  
pp. 455-456
Author(s):  
M. Yokosawa
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Event Horizon ◽  
Accretion Disk ◽  
Dynamical Evolution ◽  
Galactic Nuclei ◽  
Thick Disk ◽  
X Ray ◽  
General Relativistic ◽  
Inner Region

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.

Magnetic field and radius of the innermost stable circular orbit near super-massive black holes in active galactic nuclei

2015 ◽  
Vol 336 (10) ◽  
pp. 1013-1016 ◽  
Author(s):  
M. Yu. Piotrovich ◽  
Yu. N. Gnedin ◽  
N. A. Silant'ev ◽  
T. M. Natsvlishvili ◽  
S. D. Buliga
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Active Galactic Nuclei ◽  
Circular Orbit ◽  
Galactic Nuclei ◽  
Massive Black Holes ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit
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