scholarly journals Global Radiation-Magnetohydrodynamic Simulations of Black-Hole Accretion Flow and Outflow: Unified Model of Three States

2009 ◽  
Vol 61 (3) ◽  
pp. L7-L11 ◽  
Author(s):  
Ken Ohsuga ◽  
Shin Mineshige ◽  
Masao Mori ◽  
Yoshiaki Kato
Keyword(s):  
Black Hole ◽  
Global Radiation ◽  
Unified Model ◽  
Accretion Flow ◽  
Black Hole Accretion ◽  
Magnetohydrodynamic Simulations ◽  
Hole Accretion

scholarly journals The effects of resolution on black hole accretion simulations of jets

2020 ◽  
Vol 498 (2) ◽  
pp. 2428-2439
Author(s):  
Christopher J White ◽  
Fiona Chrystal
Keyword(s):  
Black Hole ◽  
Velocity Structure ◽  
Grid Resolution ◽  
Black Hole Accretion ◽  
General Relativistic ◽  
Axisymmetric Structure ◽  
Magnetohydrodynamic Simulations ◽  
Jet Power ◽  
Hole Accretion

ABSTRACT We perform three general-relativistic magnetohydrodynamic simulations of black hole accretion designed to test how sensitive results are to grid resolution in the jet region. The cases differ only in numerics, modelling the same physical scenario of a radiatively inefficient, geometrically thick, magnetically arrested flow on to a rapidly spinning black hole. Properties inferred with the coarsest grid generally agree with those found with higher resolutions, including total jet power and its decomposition into different forms, velocity structure, non-axisymmetric structure, and the appearance of resolved millimetre images. Some measures of variability and magnetization are sensitive to resolution. We conclude that most results obtained by limiting resolution near the jet for computational expediency should still be reliable, at least in so far as they would not be improved with a finer grid.

ACCRETION PROBLEM IN A KERR BLACK HOLE GEOMETRY VIEWED AS FLOWS IN CONVERGING–DIVERGING DUCTS

2010 ◽  
Vol 19 (13) ◽  
pp. 2059-2069
Author(s):  
K. CHAKRABARTI ◽  
M. M. MAJUMDAR ◽  
SANDIP K. CHAKRABARTI
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Mach Number ◽  
Cross Sections ◽  
Kerr Black Hole ◽  
Flat Space ◽  
Accretion Flow ◽  
Black Hole Accretion ◽  
Hole Geometry ◽  
Hole Accretion

Accretion flow on a horizon is supersonic, no matter what the flow angular momentum or the spin of the black hole is. This means that a black hole accretion can always be viewed as a flow in a flat space–time through one or more convergent–divergent ducts. In this paper, we study how the area of cross-sections must vary in order that the flow has the same properties in both systems. We show that the accretion flow experiencing a shock is equivalent to having two ducts connected back-to-back, both with a neck where the flow becomes supersonic. We study the pressure and Mach number variations for corotating, contrarotating flows and flows around a black hole with evolving spin.

scholarly journals MONTE CARLO SIMULATIONS OF THE THERMAL COMPTONIZATION PROCESS IN A TWO-COMPONENT ACCRETION FLOW AROUND A BLACK HOLE IN THE PRESENCE OF AN OUTFLOW

2010 ◽  
Vol 19 (05) ◽  
pp. 607-620 ◽  
Author(s):  
HIMADRI GHOSH ◽  
SUDIP K. GARAIN ◽  
SANDIP K. CHAKRABARTI ◽  
PHILIPPE LAURENT
Keyword(s):  
Black Hole ◽  
Low Energy ◽  
Hot Electrons ◽  
Accretion Flow ◽  
Black Hole Accretion ◽  
Bulk Motion ◽  
Scattering Effects ◽  
Two Component ◽  
Outflow Rate ◽  
Hole Accretion

A black hole accretion may have both the Keplerian and the sub-Keplerian component. In the so-called Chakrabarti–Titarchuk scenario, the Keplerian component supplies low-energy (soft) photons while the sub-Keplerian component supplies hot electrons which exchange their energy with the soft photons through Comptonization or inverse Comptonization processes. In the sub-Keplerian component, a shock is generally produced due to the centrifugal force. The postshock region is known as the CENtrifugal pressure–supported BOundary Layer (CENBOL). In this paper, we compute the effects of the thermal and the bulk motion Comptonization on the soft photons emitted from a Keplerian disk by the CENBOL, the preshock sub-Keplerian disk and the outflowing jet. We study the emerging spectrum when the converging inflow and the diverging outflow (generated from the CENBOL) are simultaneously present. From the strength of the shock, we calculate the percentage of matter being carried away by the outflow and determine how the emerging spectrum depends on the outflow rate. The preshock sub-Keplerian flow is also found to Comptonize the soft photons significantly. The interplay between the up-scattering and down-scattering effects determines the effective shape of the emerging spectrum. By simulating several cases with various inflow parameters, we conclude that whether the preshock flow, or the postshock CENBOL or the emerging jet is dominant in shaping the emerging spectrum depends strongly on the geometry of the flow and the strength of the shock in the sub-Keplerian flow.

scholarly journals Numerical parameter survey of non-radiative black hole accretion: flow structure and variability of the rotation measure

2011 ◽  
Vol 415 (2) ◽  
pp. 1228-1239 ◽  
Author(s):  
Bijia Pang ◽  
Ue-Li Pen ◽  
Christopher D. Matzner ◽  
Stephen R. Green ◽  
Matthias Liebendörfer
Keyword(s):  
Black Hole ◽  
Flow Structure ◽  
Numerical Parameter ◽  
Accretion Flow ◽  
Black Hole Accretion ◽  
Rotation Measure ◽  
Hole Accretion

scholarly journals Scale-invariance of black hole accretion: modelling emission from a black hole X-ray binary with relativistic accretion flow simulations

2019 ◽  
Vol 490 (4) ◽  
pp. 5353-5358
Author(s):  
M Mościbrodzka
Keyword(s):  
Black Hole ◽  
Near Infrared ◽  
Thermal Emission ◽  
Broad Band ◽  
Scale Invariant ◽  
X Ray ◽  
Accretion Flow ◽  
Black Hole Accretion ◽  
Sgr A ◽  
Hole Accretion

ABSTRACT We model the non-thermal emission spectrum of the extremely sub-Eddington X-ray binary system A0620-00. It is believed that this non-thermal emission is produced by radiatively inefficient ‘quiescent’ accretion on to a stellar-mass black hole present in the system. We post-process general relativistic magnetohydrodynamics (GRMHD) simulations with multiwavelength, fully polarized, relativistic radiative transfer calculations to predict broad-band spectra and emission polarization levels for a range of electron models and accretion rates. We find that a model with strong coupling of electrons and ions in the accretion disc and accretion rate of only $\dot{M}=3\times 10^{-13} \, \rm [M_\odot \, yr^{-1}]$ is able to recover the observed X-ray spectral slope, as well as the excess of linear polarization detected in the source in the near-infrared (NIR)/optical bands. Our models constrain the spectral properties of a putative relativistic jet produced in this system. In addition, we show that the magnetized winds from our hot accretion flow carry away a small fraction of the orbital angular momentum of the binary, which is unable to explain the observed rapid orbital decay of the system. GRMHD simulations similar to the present ones are often used to explain emission from sub-Eddington supermassive black holes in Sgr A* or M87; the present simulations allow us to test whether some aspects of quiescent black hole accretion are scale-invariant.

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