Random Precessing Jet and Accretion Disk at the Galactic Center

1990 ◽  
pp. 377-378
Author(s):  
M. Fujimoto ◽  
Y. Sofue
Keyword(s):  
Accretion Disk ◽  
Galactic Center

scholarly journals Can supernova shells feed supermassive black holes in galactic nuclei?

2020 ◽  
Vol 644 ◽  
pp. A72
Author(s):  
J. Palouš ◽  
S. Ehlerová ◽  
R. Wünsch ◽  
M. R. Morris
Keyword(s):  
Accretion Disk ◽  
Galactic Center ◽  
Galactic Nuclei ◽  
Rotational Axis ◽  
Average Mass ◽  
The Galaxy ◽  
Gravitational Pull ◽  
Thin Layer Approximation ◽  
Hydrodynamical Simulations ◽  
Central Parsec

Aims. We simulate shells created by supernovae expanding into the interstellar medium of the nuclear region of a galaxy, and analyze how the shell evolution is influenced by the supernova position relative to the galactic center, by the interstellar matter density, and by the combined gravitational pull of the nuclear star cluster and supermassive black hole (SMBH). Methods. We adopted simplified hydrodynamical simulations using the infinitesimally thin layer approximation in 3D (code RING) and determined whether and where the shell expansion may bring new gas into the inner parsec around the SMBH. Results. The simulations show that supernovae occurring within a conical region around the rotational axis of the galaxy can feed the central accretion disk surrounding the SMBH. For ambient densities between 103 and 105 cm−3, the average mass deposited into the central parsec by individual supernovae varies between 10 and 1000 solar masses depending on the ambient density and the spatial distribution of supernova events. Supernovae occurring in the aftermath of a starburst event near a galactic center can supply two to three orders of magnitude more mass into the central parsec, depending on the magnitude of the starburst. The deposited mass typically encounters and joins an accretion disk. The fate of that mass is then divided between the growth of the SMBH and an energetically driven outflow from the disk.

scholarly journals An Accretion Disk Model for the Innermost 200PC of the Galaxy

1994 ◽  
Vol 140 ◽  
pp. 174-175
Author(s):  
W.J. Duschl ◽  
S.v. Linden ◽  
P.L. Biermann
Keyword(s):  
Mass Flow Rate ◽  
Accretion Disk ◽  
Mass Flow ◽  
Flow Rate ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Radial Dependence ◽  
Square Root ◽  
Disk Model ◽  
The Galaxy

AbstractWe demonstrate that it is possible to understand observed radial velocities of molecular clouds close to the Galactic Center as being due to motion of this material in an accretion disk. Our models indicate a stationary disk with a radial mass flow rate of 10-1.8 Mʘ/yr with a viscosity of 1.9 · 103 pc km/s at 100 pc from the Galactic Center and a radial dependence of it, that goes approximately like the square root of the radius from the Galactic Center.

scholarly journals Stellar Disk in the Galactic Center: A Remnant of a Dense Accretion Disk?

2003 ◽  
Vol 590 (1) ◽  
pp. L33-L36 ◽  
Author(s):  
Yuri Levin ◽  
Andrei M. Beloborodov
Keyword(s):  
Accretion Disk ◽  
Galactic Center ◽  
Stellar Disk

scholarly journals X-Ray Novae and Related Systems

1992 ◽  
Vol 151 ◽  
pp. 205-214
Author(s):  
J. Craig Wheeler ◽  
Soon-Wook Kim ◽  
Shin Mineshige
Keyword(s):  
Accretion Disk ◽  
Gamma Ray ◽  
Galactic Center ◽  
Uv Spectra ◽  
Standard Theory ◽  
Recurrence Time ◽  
Good Representation ◽  
X Ray ◽  
Corotation Radius ◽  
Amplitude Profile

Accretion disk thermal instability models have been successful in accounting for the basic observations of dwarf novae and the steady behavior of nova-like systems. Models for the dwarf-nova like variability of the old nova and intermediate polar GK Per give good agreement with the burst amplitude, profile and recurrence time in the optical and UV. A month-long “precursor plateau” in the UV is predicted for the expected 1992 outburst prior to the rise to maximum in the optical and UV. The models for the time scales of the outbursts and corresponding UV spectra at maximum are consistent with the inner edge of the accretion disk being essentially constant between quiescence and outburst and a factor of four larger than the corotation radius. These conclusions represent a challenge to the standard theory of magnetic accretion. Disk instability models have also given a good representation of the soft X-ray and optical outbursts of the X-ray novae A0620-00 and GS2000+25. Formation of coronae above the disk, heated by magneto-acoustic flux from the disk, may account for the temporal and spectral properties of the hard X-ray and gamma ray emission of related sources such as Cyg X-1, GS 2023+33 (V404 Cyg), 1E 1740.7-2942 (the “Galactic Center” Einstein Source), and GS 1124-683 (Nova Muscae).

scholarly journals Random Precessing Jet and Accretion Disk at the Galactic Center

1990 ◽  
Vol 140 ◽  
pp. 377-378
Author(s):  
M. Fujimoto ◽  
Y. Sofue
Keyword(s):  
Accretion Disk ◽  
Galactic Center ◽  
Galactic Plane ◽  
Azimuthal Angle ◽  
Rotation Period ◽  
Orbital Plane ◽  
The Galaxy ◽  
Ambient Gas ◽  
Image Position ◽  
Unit Vectors

As a mechanism to generate asymmetric radio features in the central 50 pc of the Galaxy (Sofue and Fujimoto 1987), we consider a gaseous jet from the tilted accretion disk at the center and the interaction of the jet with ambient gas on the galactic plane. It is shown schematically in figure 1 that the magnetic torques N1,2,3 exert on a gaseous element ρhΔsΔr of a ring to change its tilted orbital plane, and where γ1,2,3 are constants of a factor of unity and e1,2,3 unit vectors. The azimuthal angle ϕ is measured along the rotation from the lowest part of the ring below the galactic plane. The orbital plane is tilted against the galactic plane by the angle θ The change of the angular momentum of the disk element L = ρhΔsΔrr × v is, where 〈〉 means the average over one rotation period T or over ϕ = 0 to 2π in equations (1) to (3).

scholarly journals Numerical theory of accretion flow and jet launching: A study on the galactic center

2010 ◽  
Vol 6 (S275) ◽  
pp. 102-103
Author(s):  
Salomé Dibi ◽  
Samia Drappeau ◽  
Sera Markoff ◽  
Chris Fragile
Keyword(s):  
Magnetic Field ◽  
Accretion Disk ◽  
Parameter Space ◽  
Galactic Center ◽  
Radiative Cooling ◽  
Accretion Flow ◽  
Radiative Processes ◽  
Numerical Theory ◽  
Sgr A ◽  
The Magnetic Field

AbstractWe obtained the first spectral predictions from a simulation of the Galactic Center to include radiative processes internally. We performed simulations with and without cooling, with and without spin, and for different initial configurations of the magnetic field, in order to test the effect on jet launching and inner accretion disk characteristics. By exploring parameter space, we will attempt to place new constraints on the controversial question about the presence or not of a jet from Sgr A*, as well as study jet launching in general. We have shown that, as expected, the spin of the BH affects the structure of the jet. The presence of cooling also strongly influences the inner structure of the accretion disk and therefore affects jet launching. These results show that radiative cooling is not negligible, as is usually assumed for the very underluminous supermassive BH, Sgr A*. On the contrary, the inclusion of cooling has a very visible influence on the accretion disk. Furthermore it creates an important difference in the resulting spectra.

scholarly journals MHD Aspects of Galactic Center Physics

1989 ◽  
Vol 136 ◽  
pp. 301-312
Author(s):  
J. Heyvaerts
Keyword(s):  
Magnetic Field ◽  
Energy Balance ◽  
Magnetic Fields ◽  
Accretion Disk ◽  
Galactic Center ◽  
The Sun ◽  
Physical Similarity ◽  
General Energy ◽  
Sgr A ◽  
The Magnetic Field

This review addresses the question of MHD phenomena in the galactic center, which are expectedly important in view of the large value of the magnetic field. A physical similarity with other MHD environments where magnetic fields are dominated by a dense driver and dominate a more tenuous halo is recognized. Known physics rules this type of coupling. Most proposed MHD theories of the galactic center fit, at least partly, in this general frame. One of them views Sgr A and its environment up to 50pc as an active corona, similar to that of the sun. whose driver is some central accretion disk, which may (or may not) be the molecular ring. This unified picture is outlined and is shown to naturally explain a number of otherwise puzzling observed features, such as the radio arc and bridge, possibly the ionized minispiral and some aspects of the general energy balance of this region.

Iron K-Line Emission from X-Ray Binaries

1988 ◽  
Vol 102 ◽  
pp. 47-50
Author(s):  
K. Masai ◽  
S. Hayakawa ◽  
F. Nagase
Keyword(s):  
Accretion Disk ◽  
Radiative Recombination ◽  
Characteristic Temperature ◽  
Line Emission ◽  
Ionization Front ◽  
Continuum Radiation ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx> 10 keV is likely due to fluorescence outside the He II ionization front.

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