A two-temperature accretion disk model for Cygnus X-1 - Structure and spectrum

1976 ◽  
Vol 204 ◽  
pp. 187 ◽  
Author(s):  
S. L. Shapiro ◽  
A. P. Lightman ◽  
D. M. Eardley
Keyword(s):  
Accretion Disk ◽  
Disk Model ◽  
Two Temperature

Cygnus X-1 - A two-temperature accretion disk model which explains the observed hard X-ray spectrum

1975 ◽  
Vol 199 ◽  
pp. L153 ◽  
Author(s):  
D. M. Eardley ◽  
A. P. Lightman ◽  
S. L. Shapiro
Keyword(s):  
Accretion Disk ◽  
Disk Model ◽  
X Ray ◽  
Two Temperature

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.

On the prescriptions of viscosity in an accretion disk model

2012 ◽  
Vol 341 (2) ◽  
pp. 359-362
Author(s):  
T. Kai ◽  
K. Arai
Keyword(s):  
Accretion Disk ◽  
Disk Model

scholarly journals Black-Hole Accretion Corona Immersed in the Disk Radiation Fields

1998 ◽  
Vol 188 ◽  
pp. 419-420
Author(s):  
T. Miwa ◽  
Y. Watanabe ◽  
J. Fukue
Keyword(s):  
Black Hole ◽  
Pressure Gradient ◽  
Accretion Disk ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Disk Model ◽  
Radiation Fields ◽  
Black Hole Accretion ◽  
Cold Case ◽  
Hole Accretion

We examined an accretion-disk corona around a black hole immersed in the disk radiation fields (cf. Watanabe, Fukue 1996a, b). The corona is supposed to be initially at rest far from the center. During infall above and below the disk, the corona is suffered from the disk radiation fields. As a disk model, we adopted the standard α-disk, and in order to mimic the general relativisitic effects, we use the pseudo-Newtonian force proposed by Artemova et al. (1996). Moreover, we assume that the corona is geometrically thin and optically thin, and ignored any motion such as wind. We consider the cold case, where the pressure-gradient force is ignored. Under these assumptions, we calculated the motion of the corona gas and found that the infall of corona is supressed due to disk radiation fields.

scholarly journals The Brightest Point in Accretion Disk and Black Hole Spin: Implication to the Image of Black Hole M87*

Universe ◽  
2019 ◽  
Vol 5 (8) ◽  
pp. 183 ◽  
Author(s):  
Vyacheslav I. Dokuchaev ◽  
Natalia O. Nazarova
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Accretion Disk ◽  
Disk Model ◽  
Dark Region ◽  
High Resolution Image ◽  
Supermassive Black Hole ◽  
Black Hole Spin ◽  
The Galaxy ◽  
Expected Position

We propose the simple new method for extracting the value of the black hole spin from the direct high-resolution image of black hole by using a thin accretion disk model. In this model, the observed dark region on the first image of the supermassive black hole in the galaxy M87, obtained by the Event Horizon Telescope, is a silhouette of the black hole event horizon. The outline of this silhouette is the equator of the event horizon sphere. The dark silhouette of the black hole event horizon is placed within the expected position of the black hole shadow, which is not revealed on the first image. We calculated numerically the relation between the observed position of the black hole silhouette and the brightest point in the thin accretion disk, depending on the black hole spin. From this relation, we derive the spin of the supermassive black hole M87*, a = 0.75 ± 0.15 .

scholarly journals Magnetic fields of AGNs and standard accretion disk model: testing by optical polarimetry

2009 ◽  
Vol 507 (1) ◽  
pp. 171-182 ◽  
Author(s):  
N. A. Silant'ev ◽  
M. Yu. Piotrovich ◽  
Yu. N. Gnedin ◽  
T. M. Natsvlishvili
Keyword(s):  
Magnetic Fields ◽  
Accretion Disk ◽  
Model Testing ◽  
Disk Model

scholarly journals The accretion disk paradigm for young stars

2007 ◽  
Vol 3 (S243) ◽  
pp. 1-12 ◽  
Author(s):  
Claude Bertout
Keyword(s):  
Accretion Disk ◽  
Indirect Evidence ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Young Stars ◽  
Young Stellar Objects ◽  
Recent Attempt ◽  
Disk Model ◽  
Stellar Objects ◽  
T Tauri

AbstractAccretion and magnetic fields play major roles in several of the many models put forward to explain the properties of T Tauri stars since their discovery by Alfred Joy in the 1940s. Early investigators already recognized in the 1950s that a source of energy external to the star was needed to account for the emission properties of these stars in the optical range.The opening of new spectral windows from the infrared to the ultraviolet in the 1970s and 1980s showed that the excess emission of T Tauri stars and related objects extends into all wavelength domains, while evidence of outflow and/or infall in their circumstellar medium was accumulating.Although the disk hypothesis had been put forward by Merle Walker as early as 1972 to explain properties of YY Orionis stars and although Lynden-Bell and Pringle worked out the accretion disk model and applied it specifically to T Tauri stars in 1974, the prevailing model for young stellar objects until the mid-1980s assumed that they experienced extreme solar-type activity. It then took until the late 1980s before the indirect evidence of disks presented by several teams of researchers became so compelling that a paradigm shift occurred, leading to the current consensual picture.I briefly review the various models proposed for explaining the properties of young stellar objects, from their discovery to the direct observations of circumstellar disks that have so elegantly confirmed the nature of young stars. I will go on to discuss more modern issues concerning their accretion disk properties and conclude with some results obtained in a recent attempt to better understand the evolution of Taurus-Auriga young stellar objects.

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