scholarly journals Simulations of radiation driven winds from Keplerian discs

2020 ◽  
Author(s):  
Sananda Raychaudhuri ◽  
Mukesh K Vyas ◽  
Indranil Chattopadhyay
Keyword(s):  
Black Holes ◽  
Angular Momentum ◽  
Accretion Rate ◽  
Accretion Disc ◽  
Accretion Discs ◽  
Thermal Pressure ◽  
Linear Effect ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Order Of Magnitude

Abstract We study the ejection of winds from thin accretion discs around stellar mass black holes and the time evolution of these winds in presence of radiation field generated by the accretion disc. Winds are produced by radiation, thermal pressure and the centrifugal force of the disc. The winds are found to be mildly relativistic, with speeds reaching up to terminal speeds 0.1 for accretion rate 4 in Eddington units. We show that the ejected matter gets its rotation by transporting angular momentum from the disc to the wind. We also show that the radiation drag affects the accretion disc winds in a very significant manner. Not only that the terminal speeds are reduced by an order of magnitude due to radiation drag, but we also show that the non-linear effect of radiation drag, can mitigate the formation of the winds from the matter ejected by the accretion disc. As radiation drag reduces the velocity of the wind, the mass outflow rate is reduced in its presence as well.

scholarly journals An ionized accretion disc wind in Hercules X-1

2019 ◽  
Vol 491 (3) ◽  
pp. 3730-3750
Author(s):  
P Kosec ◽  
A C Fabian ◽  
C Pinto ◽  
D J Walton ◽  
S Dyda ◽  
...  
Keyword(s):  
Accretion Rate ◽  
Compact Object ◽  
Accretion Disc ◽  
Strong Correlations ◽  
X Ray ◽  
Outflow Rate ◽  
Mass Outflow ◽  
X Ray Binaries ◽  
Absorption Features ◽  
Reflection Grating

ABSTRACT Hercules X-1 is one of the best-studied highly magnetized neutron star X-ray binaries with a wealth of archival data. We present the discovery of an ionized wind in its X-ray spectrum when the source is in the high state. The wind detection is statistically significant in most of the XMM–Newton observations, with velocities ranging from 200 to 1000 km s−1. Observed features in the iron K band can be explained by both wind absorption and a forest of iron emission lines. However, we also detect nitrogen, oxygen, and neon absorption lines at the same systematic velocity in the high-resolution Reflection Grating Spectrometer grating spectra. The wind must be launched from the accretion disc, and could be the progenitor of the ultraviolet absorption features observed at comparable velocities, but the latter likely originate at significantly larger distances from the compact object. We find strong correlations between the ionization level of the outflowing material and the ionizing luminosity as well as the superorbital phase. If the luminosity is driving the correlation, the wind could be launched by a combination of Compton heating and radiation pressure. If instead the superorbital phase is the driver for the variations, the observations are likely scanning the wind at different heights above the warped accretion disc. If this is the case, we can estimate the wind mass outflow rate, corrected for the limited launching solid angle, to be roughly 70 per cent of the mass accretion rate.

scholarly journals Magnetohydrodynamic Turbulence in Accretion Discs: Towards More Realistic Models

1997 ◽  
Vol 163 ◽  
pp. 210-214
Author(s):  
Ulf Torkelsson ◽  
Axel Brandenburg ◽  
Åke Nordlund ◽  
Robert F. Stein
Keyword(s):  
Angular Momentum ◽  
Boundary Conditions ◽  
Accretion Disc ◽  
Quantitative Change ◽  
Accretion Discs ◽  
Momentum Transport ◽  
Magnetohydrodynamic Turbulence ◽  
Accretion Flow ◽  
Angular Momentum Transport ◽  
Main Effects

AbstractThe shearing box has rapidly become the accepted way to investigate turbulence in Keplerian shear flows. In this paper we discuss to what extent and in which way the outcome of the shearing box is affected by the adopted boundary conditions, and how the shearing box can be modified to capture more of the physics of an accretion disc. The original shearing box model is too symmetric to generate a net accretion flow, but the symmetry can be broken by including the main effects of the cylindrical geometry of the real disc. However the quantitative change in the resulting angular momentum transport is small.

Mass outflow rate from accretion discs around compact objects

1999 ◽  
Vol 16 (12) ◽  
pp. 3879-3901 ◽  
Author(s):  
Tapas K Das ◽  
Sandip K Chakrabarti
Keyword(s):  
Compact Objects ◽  
Accretion Discs ◽  
Outflow Rate ◽  
Mass Outflow

scholarly journals Star formation in accretion discs and SMBH growth

2020 ◽  
Vol 493 (3) ◽  
pp. 3732-3743 ◽  
Author(s):  
Alexander J Dittmann ◽  
M Coleman Miller
Keyword(s):  
Black Holes ◽  
Star Formation ◽  
Active Galactic Nuclei ◽  
Accretion Rate ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Compact Objects ◽  
Accretion Discs ◽  
Massive Black Holes ◽  
Gas Accretion

ABSTRACT Accretion discs around active galactic nuclei (AGNs) are potentially unstable to star formation at large radii. We note that when the compact objects formed from some of these stars spiral into the central supermassive black hole (SMBH), there is no radiative feedback and therefore the accretion rate is not limited by radiation forces. Using a set of accretion disc models, we calculate the accretion rate on to the central SMBH in both gas and compact objects. We find that the time-scale for an SMBH to double in mass can decrease by factors ranging from ∼0.7 to as low as ∼0.1 in extreme cases, compared to gas accretion alone. Our results suggest that the formation of extremely massive black holes at high redshift may occur without prolonged super-Eddington gas accretion or very massive seed black holes. We comment on potential observational signatures as well as implications for other observations of AGNs.

scholarly journals Super-Eddington accretion discs with advection and outflows around magnetized neutron stars

2019 ◽  
Vol 626 ◽  
pp. A18 ◽  
Author(s):  
Anna Chashkina ◽  
Galina Lipunova ◽  
Pavel Abolmasov ◽  
Juri Poutanen
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Mass Loss ◽  
Accretion Rate ◽  
Accretion Disc ◽  
Accretion Discs ◽  
X Ray ◽  
Radial Profiles ◽  
X Ray Binaries ◽  
Eddington Limit

We present a model for a super-Eddington accretion disc around a magnetized neutron star taking into account advection of heat and the mass loss by the wind. The model is semi-analytical and predicts radial profiles of all the basic physical characteristics of the accretion disc. The magnetospheric radius is found as an eigenvalue of the problem. When the inner disc is in radiation-pressure-dominated regime but does not reach its local Eddington limit, advection is mild, and the radius of the magnetosphere depends weakly on the accretion rate. Once it approaches the local Eddington limit the disc becomes advection-dominated, and the scaling for the magnetospheric radius with the mass accretion rate is similar to the classical Alfvén relation. Allowing for the mass loss in a wind leads to an increase in the magnetospheric radius. Our model can be applied to a wide variety of magnetized neutron stars accreting close to or above their Eddington limits: ultra-luminous X-ray pulsars, Be/X-ray binaries in outbursts, and other systems. In the context of our model we discuss the observational properties of NGC 5907 X-1, the brightest ultra-luminous pulsar currently known, and NGC 300 ULX1, which is apparently a Be/X-ray binary experiencing a very bright super-Eddington outburst.

scholarly journals Hot Accretion onto Black Holes with Outflow

2018 ◽  
Vol 168 ◽  
pp. 04005
Author(s):  
Myeong-Gu Park ◽  
Du-Hwan Han
Keyword(s):  
Black Holes ◽  
Angular Momentum ◽  
Accretion Rate ◽  
Host Galaxies ◽  
Accretion Flow ◽  
Mass Accretion Rate ◽  
Viscosity Parameter ◽  
Growth History ◽  
History Of ◽  
Flow Study

Classic Bondi accretion flow can be generalized to rotating viscous accretion flow. Study of hot accretion flow onto black holes show that its physical charateristics change from Bondi-like for small gas angular momentum to disk-like for Keperian gas angular momentum. Especially, the mass accretion rate divided by the Bondi accretion rate is proportional to the viscosity parameter alpha and inversely proportional to the gas angular momentum divided by the Keplerian angular momentum at the Bondi radius for gas angular momentum comparable to the Keplerian value. The possible presence of outflow will increase the mass inflow rate at the Bondi radius but decrease the mass accretion rate across the black hole horizon by many orders of magnitude. This implies that the growth history of supermassive black holes and their coevolution with host galaxies will be dramatically changed when the accreted gas has angular momentum or develops an outflow.

scholarly journals What is wrong with steady accretion discs?

2019 ◽  
Vol 628 ◽  
pp. A121 ◽  
Author(s):  
C. J. Nixon ◽  
J. E. Pringle
Keyword(s):  
Angular Momentum ◽  
Accretion Rate ◽  
High Viscosity ◽  
Accretion Discs ◽  
Dwarf Novae ◽  
Mhd Turbulence ◽  
Angular Momentum Transport ◽  
Major Process ◽  
The Difference ◽  
The Magnetic Field

In a standard, steady, thin accretion disc, the radial distribution of the dissipation of the accretion energy is determined simply by energy considerations. Here we draw attention to the fact that while the (quasi-)steady discs in dwarf novae in outburst are in agreement with the expected emission distribution, the steady discs in the nova-like variables are not. We note that essentially the only difference between these two sets of discs is the time for which they have been in the high viscosity, high accretion rate state. In such discs, the major process by which angular momentum is transported outwards is MHD turbulence. We speculate that such turbulence gives rise to corona-like structures (here called magnetically controlled zones, or MCZs) which are also able to provide non-negligible angular momentum transport, the magnitude of which depends on the spatial scale L of the magnetic field structures in such zones. For short-lived, high accretion rate discs (such as those in dwarf novae) we expect L ∼ H and the MCZ to have little effect. But, with time (such as in the nova-like variables) an inverse cascade in the MHD turbulence enables L, and the net effect of the MCZ, to grow. We present a simple toy model which demonstrates that such ideas can provide an explanation for the difference between the dwarf novae and the nova-like variable discs.

scholarly journals Simulation of AGN feedback and its impact on galaxies

2016 ◽  
Vol 12 (S324) ◽  
pp. 231-234
Author(s):  
Martin A. Bourne
Keyword(s):  
Black Holes ◽  
Large Scale ◽  
Accretion Disc ◽  
Moving Mesh ◽  
Host Galaxy ◽  
Scaling Relations ◽  
Mass Outflow ◽  
Phase Medium ◽  
Energy Conserving ◽  
Multi Phase

AbstractFeedback released during the growth of supermassive black holes is expected to play a key role in shaping black hole-host galaxy co-evolution. Powerful, accretion disc driven winds have been invoked to explain both observed scaling relations (e.g., M − σ) and large-scale outflows with mass outflow rates of ~ 100 − 1000 M⊙ yr−1 and momentum rates of up to ~ 30 LAGN/c. Critically, how these winds couple to the host galaxy depends on if they are momentum or energy conserving. I outline observational signatures that could distinguish between these regimes and discuss their roles in establishing galaxy properties. Furthermore, I discuss high-resolution simulations exploring feedback in a multi-phase medium, highlighting how structural properties of galaxies can impact feedback efficiency. Finally, feedback, in the form of collimated jets, is expected to regulate cooling in galaxy clusters. I discuss new simulations of jet feedback using the moving-mesh code AREPO and outline the scope of our new study.

Sign in / Sign up

Export Citation Format

Share Document