scholarly journals MHD Accretion Disk Winds: The Key to AGN Phenomenology?

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 13 ◽  
Author(s):  
Demosthenes Kazanas
Keyword(s):  
Black Hole ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Mass Flux ◽  
Accretion Rate ◽  
Compact Object ◽  
Mass Scale ◽  
Observational Constraints ◽  
X Ray ◽  
Mass Accretion Rate

Accretion disks are the structures which mediate the conversion of the kinetic energy of plasma accreting onto a compact object (assumed here to be a black hole) into the observed radiation, in the process of removing the plasma’s angular momentum so that it can accrete onto the black hole. There has been mounting evidence that these structures are accompanied by winds whose extent spans a large number of decades in radius. Most importantly, it was found that in order to satisfy the winds’ observational constraints, their mass flux must increase with the distance from the accreting object; therefore, the mass accretion rate on the disk must decrease with the distance from the gravitating object, with most mass available for accretion expelled before reaching the gravitating object’s vicinity. This reduction in mass flux with radius leads to accretion disk properties that can account naturally for the AGN relative luminosities of their Optical-UV and X-ray components in terms of a single parameter, the dimensionless mass accretion rate. Because this critical parameter is the dimensionless mass accretion rate, it is argued that these models are applicable to accreting black holes across the mass scale, from galactic to extragalactic.

scholarly journals Hybrid Accretion-Disks in AGN and the AGN Contribution to the XRB

1994 ◽  
Vol 159 ◽  
pp. 491-491
Author(s):  
Amri Wandel
Keyword(s):  
Accretion Disk ◽  
Accretion Disks ◽  
Power Law ◽  
Accretion Rate ◽  
Bremsstrahlung Spectrum ◽  
Spectral Evolution ◽  
X Ray ◽  
X Ray Background ◽  
Inner Region ◽  
Two Temperature

The hybrid accretion-disk (HAD) model links the two characteristic components of AGN spectra – the UV bump and the X-ray power-law – in the framework of one physical model. The radially stratified hybrid disk is a self consistent combination of a thin, cool accretion disk at large radii, with an inner hot two-temperature disk. Its spectrum consists of three components, corresponding to the three radial disk regions: a blackbody thermal spectrum from the outer cool disk, a Comptonized soft photon power-law spectrum from the intermediate region, and a thermal Comptonized bremsstrahlung spectrum from the inner region. The dependence of the hybrid disk spectrum on the accretion rate and on other parameters is discussed and applied to AGN spectral evolution, and in particular to explaining the cosmic X-ray background by AGN.

Polarization properties of iron emission lines as a tool to identify the finite thickness of disks with moderately super-eddington accretion rate

2021 ◽  
pp. 2150074
Author(s):  
Ze-Yuan Tang ◽  
Ye-Fei Yuan
Keyword(s):  
Accretion Disk ◽  
Accretion Disks ◽  
Accretion Rate ◽  
Finite Thickness ◽  
Polarization Degree ◽  
Iron Line ◽  
Disk Thickness ◽  
X Ray ◽  
X Ray Binaries ◽  
Polarized Radiation

The Fe-K[Formula: see text] fluorescence lines are commonly observed in AGNs and X-ray binaries. The lines are believed to be originated from the reflection of the hard X-ray continuum near the inner-most region of the accretion disks of black holes. The geometry of the accretion disk is usually assumed to be infinitely thin, but this assumption is not appropriate when the accretion rate is moderately super-Eddington. With the increase of the accretion rate, the disk becomes thick, which will significantly affect the properties of the fluorescence lines. For instance, the polarized radiation is strongly depended on the geometry of the accretion disk. In this work, based on the lamp-post model, we study the polarization properties of the relativistic Fe-K[Formula: see text] lines from thick disks in the framework of fully general relativity. We find that with the increase of the disk thickness, the polarization degree (PD) at the blue edge of the iron line increase significantly, and there appears a peak at the profile of the PD of the iron emission line, which at most is one order higher that of the line from the thin disk. Thus, the polarization properties of relativistic broad Fe-K[Formula: see text] lines can be used to as a tool to diagnose the disk thickness.

scholarly journals The X-Ray Binary KS 1731{260: Possible Analogy with Her X-1

2014 ◽  
Vol 1 (1) ◽  
pp. 246-250
Author(s):  
Vojtěch Šimon
Keyword(s):  
Neutron Star ◽  
Accretion Disk ◽  
Cycle Length ◽  
Accretion Rate ◽  
Variable Mass ◽  
X Rays ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Variable Impact

The X-ray binary with the neutron star (NS), KS 1731-260, displays superorbital cycle similar to that in Her X-1. The accretion disk had the memory of the cycle-length even when this modulation sometimes disappeared in the main outburst of KS 1731-260, and during anomalous low state in Her X-1. The disk still existed during such seasons. Although irradiation of the disk by X-rays is a viable explanation for the disk precession and warping (see model of Foulkes et al.), the mechanisms which give rise to the observed X-ray modulation are quite dierent for each of these systems. Variable absorption can explain this cycle only in Her X-1. We propose a variable mass accretion rate onto the NS in KS 1731-260 due to a highly variable impact of the inflowing mass stream with the changing phase of the cycle.

Testing propagating mass accretion rate fluctuations model PROPFLUC on black hole X-ray binaries

2016 ◽  
Vol 337 (4-5) ◽  
pp. 524-528
Author(s):  
S. Rapisarda ◽  
A. Ingram ◽  
M. van der Klis
Keyword(s):  
Black Hole ◽  
Accretion Rate ◽  
X Ray ◽  
Mass Accretion Rate ◽  
X Ray Binaries

scholarly journals Observational Constraints on the Dependence of Radio‐Quiet Quasar X‐Ray Emission on Black Hole Mass and Accretion Rate

2008 ◽  
Vol 176 (2) ◽  
pp. 355-373 ◽  
Author(s):  
Brandon C. Kelly ◽  
Jill Bechtold ◽  
Jonathan R. Trump ◽  
Marianne Vestergaard ◽  
Aneta Siemiginowska
Keyword(s):  
Black Hole ◽  
Accretion Rate ◽  
Observational Constraints ◽  
Black Hole Mass ◽  
X Ray

scholarly journals Disk Instabilities in the Black Hole Binaries

1996 ◽  
Vol 158 ◽  
pp. 135-138 ◽  
Author(s):  
J. K. Cannizzo
Keyword(s):  
Black Hole ◽  
Accretion Disk ◽  
Time Constant ◽  
Accretion Disks ◽  
Binary Systems ◽  
Recent Progress ◽  
Light Curves ◽  
X Ray ◽  
Black Hole Binaries ◽  
Exponential Character

I will briefly review recent progress in our understanding of the global propagation of accretion disk instabilities operating in interacting binary systems in which the accreting star is a ~ 10 M⊙ black hole. A detailed discussion of this work can be found in Cannizzo, Chen & Livio (1995).The X-ray light curves of the brightest and best studied X-ray novae – systems such as A0620–00, GS2000+25, GS1124–68, and GRO J0422+32 – are notable in two respects: the rise times are fast (a few days) and the decays have an exponential character, where the e–folding time constant is about 30 to 40 d (Mineshige, Yamasaki, & Ishizaka 1993, hereafter MYI). It is noteworthy that outbursts in dwarf novae also decay exponentially, with the time constant being about a factor of 10 shorter. In this contribution I will discuss the constraints on the physics of accretion disks which the (observed) exponential decay enables us to make.

JET FORMATION IN MICROQUASARS AND ACTIVE GALACTIC NUCLEI: MAGNETIC FIELD LIMITS

2008 ◽  
Vol 17 (10) ◽  
pp. 1931-1937
Author(s):  
M. M. KAUFMAN BERNADÓ ◽  
M. MASSI
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Accretion Rate ◽  
Plasma Pressure ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Disk Material ◽  
The Magnetic Field

We introduce the use of a well-known parameter, the Alfvén Radius, R A , as a new tool to discern whether an X-ray binary system may undergo a microquasar phase, i.e. ejecting relativistic particles orthogonal to the accretion disk. We study what we call the basic condition, R A /R* = 1 in its dependency on the magnetic field strength and the mass accretion rate. With this basic condition we establish under which combination of parameters any class of accreting neutron stars could become a microquasar instead of confining disk-material down to the magnetic poles and creating the two emitting caps typical for an X-ray pulsar. In the case of black-hole accreting binaries we equate the magnetic field pressure to the plasma pressure in the last stable orbit (i.e. R A /R LSO = 1) and we get upper limits for the magnetic field strength as a function of the mass accretion rate and the black hole mass.

scholarly journals Probing Supercritical Accretion in Ultraluminous X-ray Source M82 X-1 by means of X-ray Spectral Evolution Analysis

2020 ◽  
Vol 240 ◽  
pp. 07005
Author(s):  
Izatul Hafizah ◽  
Kiki Vierdayanti
Keyword(s):  
Black Hole ◽  
Binary System ◽  
Accretion Rate ◽  
Spectral Evolution ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Blackbody Model ◽  
Chi Squared ◽  
Dominant State ◽  
Black Hole Binary

We analyze the spectral evolution of ultraluminous X-ray source (ULX) M82 X-1 by means of spectral fitting. We use selected Swift/XRT data in 2014 and 2015. The flux of M82 X-1 increased by a factor of 2-3 from 2014 to 2015. Most of the data in 2015 show greater dominance of hard component than those of 2014. Due to moderate signal-to-noise ratio, we only fit each spectrum with power-law and disk blackbody model separately. The data in 2014 are better fitted with powerlaw model based on the value of reduced-chi squared. On the other hand, both powerlaw and diskbb models showed comparable re- duced chi-squared value for the data in 2015. We found that the range of spectral index for 2014 data is 1.65 < Γ < 2.08 and for 2015 data is 1.02 < Γ < 1.95 from the powerlaw model, resembling the range for that of black hole binary system at low mass accretion rate. We obtained higher innermost disk temper- ature from the disk blackbody model, 1.20 keV < Tin < 3.63 keV, compared to that of black hole binary system in the thermal state. The calculated innermost radius of the disk, Rin, varies between 0.99 to 4.89 RS assuming 10 M0 black hole which indicates that the spectral state is not in thermal dominant state but rather we suspect that M82 X-1 exhibits greater mass accretion rate than that of the thermal dominant state.

scholarly journals Ultraluminous X-ray sources with flat-topped noise and QPO

2019 ◽  
Vol 486 (2) ◽  
pp. 2766-2779 ◽  
Author(s):  
Kirill Atapin ◽  
Sergei Fabrika ◽  
Maria D Caballero-García
Keyword(s):  
Black Hole ◽  
Power Density ◽  
Root Mean Square ◽  
Accretion Rate ◽  
Mean Square ◽  
Periodic Oscillations ◽  
Simple Interpretation ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Ngc 6946

ABSTRACT We analysed the X-ray power density spectra of five ultraluminous X-ray sources (ULXs) NGC 5408 X-1, NGC 6946 X-1, M 82 X-1, NGC 1313 X-1, and IC 342 X-1 that are the only ULXs that display both flat-topped noise (FTN) and quasi-periodic oscillations (QPOs). We studied the QPO frequencies, fractional root-mean-square (rms) variability, X-ray luminosity, and spectral hardness. We found that the level of FTN is anticorrelated with the QPO frequency. As the frequency of the QPO and brightness of the sources increase, their fractional variability decreases. We propose a simple interpretation using the spherization radius, viscosity time, and α-parameter as basic properties of these systems. The main physical driver of the observed variability is the mass accretion rate that varies ≳3 between different observations of the same source. As the accretion rate decreases the spherization radius reduces and the FTN plus the QPO move towards higher frequencies, resulting in a decrease of the fractional rms variability. We also propose that in all ULXs when the accretion rate is low enough (but still super-Eddington) the QPO and FTN disappear. Assuming that the maximum X-ray luminosity depends only on the black hole (BH) mass and not on the accretion rate (not considering the effects of either the inclination of the super-Eddington disc or geometrical beaming of radiation), we estimate that all the ULXs have about similar BH masses, with the exception of M 82 X-1, which might be 10 times more massive.

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