Accretion Disk Coronae were first suggested to explain the incomplete eclipses and shallow profiles observed from some Low Mass X-ray Binaries (White and ...
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THE X-RAY SPECTRA OF AGN ACCRETION DISK CORONAE: FIRST RESULTS A. Orr 1;2 , G. Torricelli of the present paper. The model In our model (described in detail by Torricelli et al., in preparation) we
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It is plausible that an accretion disk pumps energy into an outer tenuous layer of its atmosphere to form a high-tmeperature corona analogous to the solar corona. General features of such a corona, not specific to any model, are discussed, and order-of-magnitude estimates are made for the ...
Energy Citations Database
We present the properties of accretion disk corona (ADC) models in which the radiation field, the temperature, and the total opacity of the corona are determined self-consistently. We use a nonlinear Monte Carlo code to perform the calculations. As an exa...
National Technical Information Service (NTIS)
It is shown that the de-excitation of convection elements in accretion disks considerably reduces convective energy transfer. The energy transferred by floating-up magnetic field tubes is also small. Therefore, radiative transfer is the main mechanism of energy transfer. It is concluded that hot coronae cannot exist around ...
The structure of Compton-heated coronae above accretion disks is studied here by using analytic and numerical approaches are used here to determine the direct and scattered radiation reaching the base of the corona for a range of central source luminosities. It is found that the outer region of the ...
A model is worked out for the inner zone of an accretion disk, allowing for the existence of a vertical velocity component for the gas. The temperature in the central plane of the disk is found to be higher than in the standard theory, and it depends on the accretion rate. Some of the gas in the inner zone is shed, ...
Theory and Modelling Research in the LHEA - Research Topics. Low Mass X-ray Binaries -- Accretion Disk Corona Radiative Transfer � Synthetic X-ray Spectra ...
An algorithm has been developed that will carry out detailed, two-dimensional, fully self-consistent
NASA Technical Reports Server (NTRS)
of an accretion disk initially threaded by a uniform poloidal magnetic field in a non-rotating corona (either in a state of steady fall or in hydrostatic ...
- tonizing corona/cloud is illuminated by the soft photon emission from a cold, outer disk that does not penetrate much in to the corona. We assume that the energy is injected to the corona by two channels: a non laws for the luminosity of the cold disk, the thermal dissipation/heating rate in ...
Sep 10, 2008 ... Intro/Motivation. Ray-Tracing. Disk/Corona Model. Results. Applications. X-Ray Polarization from Accreting Black Holes. Jeremy Schnittman ...
HD101088 is a young binary accreting from a tenuous circumprimary and/or circumsecondary disk despite the apparent lack of a massive dusty circumbinary disk. We propose to observe it with RGS with an exposure of 60 ks to detect the emission lines from the O VII He-like ion and look for potential high-density plasma at the base of the ...
NASA Astrophysics Data System (ADS)
Recent observations of partial X-ray eclipses from 4U1822-37 have shown that the central X-ray source in this system is diffused by a large Compton-thick accretion disk corona (ADC). Another binary, 4U2129-47, also displays a partial eclipse and contains ...
We apply our self-consistent accretion disk corona (ADC) model, with two different geometries, to the broadband X-ray spectrum of the black hole candidate Cygnus X-1. As shown in a companion paper, models in which the Comptonizing medium is a slab surroun...
We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well-studied black hole binaries, we ...
PubMed
Recent work on a unified model of accretion flows and X-ray emission in low mass X-ray binaries is summarized. In this model, a weakly magnetic neutron star accretes gas simultaneously from a Keplerian disk and a corona above the inner part of the disk. P...
We investigate the model of disk/coronal accretion into a black hole. We show that the inner regions of an accretion disk in X-ray binaries can transform from a cool standard disk to an advection-dominated flow through the known properties of Coulomb interaction in a two-temperature plasma, ...
We herein present an observational and theoretical review of the winds of compact binaries. After a brief consideration of the accretion disk coronae and winds of X-ray binaries, the review concentrates on the winds of cataclysmic variables (CVs). Specifically, we consider the related problems of the geometry and mass-loss rate of the ...
The stability of magnetic fields within the accretion disks is examined, including the effects of magnetic buoyancy. Rayleigh-Taylor, and Kelvin-Helmholtz instabilities. The purpose of the study is to examine the efficacy of turbulent accretion (..cap alpha..-) disk models which depend upon ...
The polarization of X radiation from an accretion disk in a binary X-ray source is investigated. Calculations are discussed which indicate that radiation from an accretion disk is linearly polarized as a result of Thomson scattering, that the hard X-ray electric vector lies in the orbital plane in the standard ...
We propose a two-component model consisting of a standard thin accretion disk and a hotter corona for 3U 1820--30, with the giant X-ray bursts originating in the inner (radiation-pressure dominated) region of the disk. Arguments in favor of and methods to test such a model are briefly discussed. Parameters of the ...
The X-ray spectrum from a cool accretion disk heated by virialized protons is computed. The cool disk is either embedded in a magnetically heated accretion disk corona or partly extends into an ion supported torus (or ADAF). We calculate the stationary equilibrium between ...
A model for the central engine of active galactic nuclei (abbreviated as AGN) has been constructed to simultaneously explain their UV bump and X-ray spectra. It is based on an accretion disk model around a supermassive black hole in that a cold optically thick disk is surrounded by a hot 'corona' and that energy ...
Accretion Disk Coronae J. Wilms 1 J.B. Dove 2 , M.A. Nowak 3 , and M.C. Begelman 3 1 Institut f as well as several alternative configurations (Dove et al., 1997a,b; Wilms et al., 1997). The physical is sandwiched between two accre� #12; 2 J. Wilms et al.: Accretion Disk ...
Non-thermal X-ray emission in compact accretion engines can be interpreted to result from magnetic dissipation in an optically thin magnetized corona above an optically thick accretion disk. If coronal magnetic field originates in the disk and the disk is turbulent, then ...
Accreting neutron stars provide the bulk of high luminosity X-ray sources. Decade long studies of low-mass X-ray binaries have provided a wealth of information about the various nature of X-ray emissions and proposed emission sites include the neutron star surface, an immediate boundary layer, the inner disk region, a possible compact ...
Within the framework of unsaturated Compton disk accretion onto a supermassive black hole as model for power-law active galactic nuclei X-ray sources (as opposed to the synchro-Compton model), we compare the hot inner disk model of Shapiro, Lightman, and Eardley and the disk corona model with ...
We present preliminary results from the analysis of an RXTE observation of Cyg X-1 in the hard state. We show that the observed X-ray spectrum can be explained with a model for an accretion disk corona (ADC), in which a hot sphere is situated inside of a ...
Accretion disk coronae in high-luminosity systems ... Author(s): Band, David L.; Klein, Richard I.; Castor, John I.; Nash, J. K. ...
PROPERTIES OF ACCRETION DISK CORONAE J. Wilms 1 , J. Dove 2 , R. Staubert 1 , M. C. Begelman 2 1 & Rees 1988; Grebenev et al. 1993; Mai� sack et al. 1993; Wilms et al. 1996 and references therein of Cyg X�1 (Wilms et al. 1996) and a model with a final optical depth of 0.22 and an average temperature
accretion disks in the western Gulf region (Texas and Louisiana). Accretion ... protostellar disks are believed to be accretion disks associated with young, ...
The thermal equilibrum structure and dynamical behavior of externally irradiated accretion disks are investigated. For radiative disks only the surface layer is heated, while for convective disks the heat penetrates deeply into the disk. For sufficiently strong radiation and given irradiation ...
Thermal conduction between a cool accretion disk and a hot inner corona can result in either evaporation of the disk or condensation of the hot corona. At low mass accretion rates, evaporation dominates and can completely remove the inner disk. At ...
A model for the fluctuating hard component of intense cosmic X-ray sources (such as Cyg X-1) is developed, based upon the amplification of magnetic fields by convective motions and differential rotation within a hot (T> or approx. =10/sup 6/K) accretion disk. Field reconnection within the inner portion of the disk is shown to be ...
Observations of T Tauri stars and young brown dwarfs suggest that the accretion rates of their disks
We calculate the structure of an effectively optically thin and geometrically thin accretion disk in
A model for disk accretion by a rotating magnetic neutron star is proposed which includes a detailed
It is demonstrated through nonlinear numerical simulations that there are two kinds of magnetic accretion disks. One is a high-beta disk, called a solar-type disk, where magnetic flux escapes from the disk due to magnetic buoyancy (or Parker) instability to produce a (low-beta) hot ...
accretion? " What is the structure of the inner disk? " How do accretion disks drive jets? ... IXO will reveal the physics of disk accretion, and low L_X ...
Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveals a three-layered atmospheric structure in the inner region of their accretion disks. Above the cold and optically thick disk with a temperature of 0.2 to 0.5 kiloelectron volts, there is a warm layer with a temperature of 1.0 to ...
The stability and evolution of windy accretion disks is investigated in detail. The basic disk evolution equations are briefly recapitulated, and an idealized analytic treatment of the wind and viscosity is used to show that steady disk flow is indeed unstable for sufficiently large ratio of the mass loss rate in ...
Black holes, lurking at the centers of distant galaxies, feed on gas to become quasars. The bulk of the powerful emission from radio-quiet quasars originates from two structures close to the central black hole: the accretion disk and the hot corona. The disk-corona relationship and its dependence on the rate of gas ...
In paper 1 (Chakrabarti & D'Silva 1994), we have studied the conditions under which flux tubes are expelled from adiabatic thick accretion disks. In the present paper, we explore a few other models of thick disks, where flux tubes could be stored. We show that flux tubes with sufficiently weak fields are not expelled out if they ...
Models are presented for the 6-7 keV iron line emission from low-mass X-ray binaries. A simplified model for an accretion disk corona is used to examine the dependence of the observable line properties, line width and mean energy, on the radial distance of the emission region from the X-ray source, and on the fraction of the X-rays ...
The spectral evolution of accretion disks in X-ray binaries containing black holes is studied, based on the disk instability model. The thermal transition of the outer portions of the disk controls the mass flow rate into the inner portions of the disk, thus modulating the soft X-ray flux which ...
Observations of X-ray binaries indicate substantial half-thicknesses for the accretion disks in these systems (up to h/R ? 0.25, where h is the disk half-thickness and R its radius), while standard ? accretion disks predict appreciably smaller half-thicknesses. We study the theoretical vertical ...
X-ray reflection features observed from the innermost regions of accretion disks in active galactic nuclei (AGNs) allow important tests of accretion theory. In recent years, it has been possible to use the Fe K? line and reflection continuum to parameterize the ionization state of the irradiated inner accretion ...
We investigate the iron K$\\alpha$ fluorescent line produced by hard X-ray photons from magnetic reconnection-heated corona. The hot corona with temperature being about $10^9$K can irradiate the underlying disk with a continuum X-ray spectrum produced via thermal Comptonization. Then the iron atoms in the disk ...
We investigate the launching and stability of extragalactic jets through magnetohydrodynamic simulations of jet evolution. In these simulations, a small scale equilibrium magnetic corona is twisted by a differentially rotating accretion disk. Two-dimensional calculations show the formation of a collimated outflow. This outflow is ...
We propose to obtain a Chandra/HETGS spectrum of IM Lup with an exposure of 150 ks. IM Lup is the only known X-ray bright transition object between the classical T Tauri star phase and the weak-lined T Tauri phase. IM Lup shows an IR excess, but its Halpha equivalent width is small, indicating very low accretion rates. The Chandra spectrum will provide important information on ...
We analyze the physical properties and infall rates of the circum-galactic gas around disks obtained in multi-resolved, cosmological, AMR simulations. At intermediate and low red-shifts, disks are embedded in an extended, hot, tenuous corona that contributes largely in fueling the disk with non-enriched gas whereas ...
High Energy Astrophysics: Accretion Disks II 1/59 Accretion Disks II 1 The dynamical equations Astrophysics: Accretion Disks II 2/59 The simplest accretion disc model to construct is that of the thin disc on the azimuthal angle z #12;High Energy ...
data yield the accretion disk thickness, diameter, electron density, and magnetic field. Introduction. The structure of AGN accretion disks on sub-parsec ...
The structure of AGN accretion disks on sub-parsec scales can be probed t,hrough ... GHz to map absorption caused by an inner accretion disk. ...
Nov 19, 2004 ... In an accretion disk, material near the outside moves slower than ... Depending on the angle at which we observe the accretion disk, ...
Jan 29, 2010 ... KY Relativistic Accretion Disk models. A set of models from Dovciak et al. (2004 ) for accretion disk spectra in the strong gravity regime. ...
do not have accretion disks. Optical spectra are the only way that we can .... inner accretion disks) confirms the asymmetrical distribution of such stars ...
Sep 27, 2002 ... Accretion Disk Simulation ... Instead, the graphic shows spiral shock waves in a three dimensional simulation of an accretion disk -- material ...
The canonical hard state is associated with emission from all three fundamental accretion components: the accretion disk, the hot accretion disk corona and the jet. On top of these, the hard state also hosts very rich temporal variability properties (low frequency QPOs in ...
High Energy Astrophysics: Accretion Disks I 1/60 Accretion Disks I References: Accretion Power in Astrophysics, J. Frank, A. King and D. Raine. High Energy Astrophysics, Vol. 2, M.S. Longair, Cambridge Astrophysics: Accretion Disks I 2/60 1 Overview ...
An interesting feature found in X-ray binary observations is the change between a soft and a hard spectrum. Such transitions were observed for both neutron star and black hole systems. The soft and hard spectral state are understood as originating from accretion via a disk which reaches inward to the compact object, in the first case, or an ...
We apply our self-consistent accretion disk corona (ADC) model, with two different geometries, to the broadband X-ray spectrum of the black hole candidate Cygnus X-1. As shown in a companion paper, models in which the Comptonizing medium is a slab surrounding the cold accretion disk cannot have ...
Disks, Accretion. USE. ACCRETION DISKS. Disks, Optical. USE. VIDEO DISKS. Disposal (In Space), Hazardous Material. USE. HAZARDOUS MATERIAL DISPOSAL (IN ...
A disk model with gas pressure viscosity. The spectrum from an accretion disk ... viscosity scales as the gas pressure. From Stella and Rosner 1984, ApJ, ...
We analyze a suite of global magnetohydrodynamic (MHD) accretion disk simulations in order to determine whether scaling laws for turbulence driven by the magnetorotational instability, discovered via local shearing-box studies, are globally robust. The simulations model geometrically thin disks with zero net magnetic flux and no ...
We present preliminary results from the analysis of an R.XTE observation of Cyg X-1 in the hard state. We show that the observed X-ray spectrum can be explained with a model for an accretion disk corona (ADC), in which a hot sphere is situated inside of a cold accretion disk (similar to an ...
The purpose of the two-day Workshop on Physics of Accretion Disks Around Compact and Young Stars was
Equations for the structure and appearance of supercritical accretion disks and the radiation-driven
An effort is made to observationally constrain accretion disks on the basis of light curves from the
. The times of eclipse can be advanced or delayed by 0.03 or more in orbital phase. X-RAY BINARY MS 1603; accepted 2008 May 27 ABSTRACT We present CCD photometry of the low-mass X-ray binary UW Coronae Borealis 1603.6+2600, UW CrB) -- X-rays: binaries 1. INTRODUCTION The interacting binary UW CrB is the optical
We discuss the application of meridionally self-similar models to winds and jets from hot coronae, in particular in the central region of accretion disks. A summary of how they may help understanding the evolution of jets from young stars is outlined. Then we discuss their application to the classification of AGN jets and extension to ...
A possible accretion model associated with the ionization instability of quasar disks is proposed to
KU Cyg is an eclipsing binary consisting of an F-type star accreting through a large accretion disk from a K5III red giant. Here we present the discovery of a 5 year dip around 1900 found from its 100 year DASCH light curve. It showed a ~0.5 mag slow fading from 1899 to 1903 and brightened back around 1904 on a relatively shorter ...
The radio-loud Narrow-Line Seyfert 1 galaxy PKS 0558-504 is a highly variable, X-ray bright source with super-Eddington accretion rate and a powerful radio jet, and hence represents an ideal laboratory to study the link between accretion and ejection phenomena. Here we present the preliminary results from an ongoing multiwavelength monitoring campaign that ...
0.6 and 1.1 keV from the iron L shell and the K shell of oxygen, nitrogen and other medium-Z. elements (e.g. Kahn, Seward and Chlebowski 1984; Vrtilek et al ...
A mechanism for the transition between low/hard, high/soft, and steep power law (SPL) spectral states in black hole X-ray binaries is proposed. The low/hard state is explained by the development of a magnetically arrested accretion disk attributable to the accumulation of a vertical magnetic field in a central bundle. This disk forms ...
The Monte Carlo Method was used to estimate the level of polarization from axisymmetric accretion disks similar to those in low-mass X-ray binaries and some classes of cataclysmic variables. In low-mass X-ray binaries electron scattering is supposed to be the dominant opacity source in the inner disk, and most of the optical light is ...
During the T Tauri phase, there is a differentially rotating region attached to the top of the stellar convective layer connecting the star with the accretion disk that rotates significantly faster than the stellar surface; rotation periods during the TT phase are about 7-8 days (?_* = 0.8-0.9 day^{-1}) while the Keplerian frequency is: ?_k = 11.1 day^{-1} ...
Nov 6, 2000 ... "accretion" means collecting of additional material. Two major places where astronomers see accretion disks are in binary star systems (two ...
Sep 4, 1998 ... 3. Formation of an Accretion Disk. Bonnet-Bidaud and van der Klis (1979) showed that even if the accretion is from the stellar wind, ...
Recent observations of partial X-ray eclipses from 4U1822-37 have shown that the central X-ray source in this system is diffused by a large Compton-thick accretion disk corona (ADC). Another binary, 4U2129-47, also displays a partial eclipse and contains an ADC. The possible origin of an ADC is discussed and a simple hydrostatic ...
Context. The number of strong iron K? line detections in Seyfert AGN is clearly growing in the Chandra, XMM-Newton and Suzaku era. The iron emission lines are broad, some are relativistically blurred. These relativistic disk lines have also been observed for galactic black hole X-ray binaries. Thermal components found in hard spectra were interpreted as an indication for a ...
We present new calculations of X-ray polarization from accreting black holes (BHs), using a Monte Carlo ray-tracing code in full general relativity. In our model, an optically thick disk in the BH equatorial plane produces thermal seed photons with polarization oriented parallel to the disk surface. These seed photons are then ...
The formation and evolution of an accretion disk formed during the collapse of a rotating cloud core
A scenario for the central engine of AGN has been developed, consisting of a massive black hole (MBH) onto which gas accretes through an accretion disk. The accretion disk radiates the observed optical and ultraviolet continua. Surrounding the MBH is a no...
Approaching the 14th anniversary of the first observations of GRS 1915+105 with RXTE, we present new results from a joint RXTE/Chandra study of the remarkable X-ray spectral variability of this enigmatic microquasar. For the first time, we are able to show that changes in the broadband X-ray spectrum (RXTE) on timescales of seconds are associated with changes in absorption lines (Chandra HETGS) ...
290 Stepinski:On Maonetic Dynamos in Thin Accretion Disks Around Stars pressure is smaller than gas pressure, otherwise the assumption of a thin disk ...
They could see details as fine as the neutron star's accretion disk, a ring of gas swirling around and flowing onto the neutron star, as the disk buckled ...
accretion disk where the viscosity is dominated by radiation pressure. ... viscosity norm. 2. 2cos /i d where i is the inclination of the disk and d is the ...
I point to an interesting similarity in the radio and the soft X-ray light curves between the November 2009 outburst of the X-ray binary Aquila X-1 and some solar flares. The ratio of the soft X-ray and radio luminosities of Aquila X-1 in that outburst is also similar to some weak solar flares, and so is the radio spectrum near 8 GHz. Based on these, as well as on some other recent studies that ...
I point to an interesting similarity in the radio and the soft X-ray light curves between the 2009 November outburst of the X-ray binary Aquila X-1 and some solar flares. The ratio of the soft X-ray and radio luminosities of Aquila X-1 in that outburst is also similar to some weak solar flares, as is the radio spectrum near 8 GHz. Based on these as well as on some other recent studies that point ...
Cool stars represent a rich source of EUV radiation promising unique information on physical processes relevant to stellar atmospheres, magnetic activity, mass transfer, and mass loss. Hot plasma can be associated with cool stars in stellar chromospheres and coronae, in disk structures surrounding cool stars, in magnetically confined material, and as a ...
Derivations are made for the mass and the mass-turnover time scale of an accretion disk as a function of the accretion rate, the observed disk radius, the non-viscous disk radius, and two parameters. These parameters depend on the effectiveness of viscosity and tidal angular momentum loss. ...
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Derivations are made for the mass and the mass-turnover time scale of an accretion disk as a function of the accretion rate, the observed disk radius, the non-viscous disk radius, and two parameters. These parameters depend on the effectiveness of viscosi...
Too hot accretion disks in ULX and superluminal jet sources ... Standard accretion disk around Kerr black hole can explain the hard disk spectra? ...
A deep (489 ks) Chandra High Energy Transmission Grating spectrum of the classical T Tauri star TW Hydrae shows a new type of coronal structure that is produced by the accretion process. In the standard model for a stellar dipole, the magnetic field truncates the disk and channels the accreting material onto the star. The He-like ...
Accretion disks are invoked to explain a host of astrophysical phenomena, from protostellar objects to AGN. And yet the mechanism allowing accretion disks to operate are completely unknown. This proposal seeks to observe the ``smoking gun'' signature of magnetically-driven viscosity in ...
Magnetic energy release plays an important role in a wide variety of cosmic objects such as the Sun, stellar coronae, stellar and galactic accretion disks and pulsars. The observed radio, X-ray and ?-ray emission often directly results from magnetic 'flares', implying that these processes are spatially fragmented and of an impulsive ...
We study the possibility that the event that loads the jet with matter from the accretion disk or the surrounding corona could also cause a flare comparable to those happening in the jet. We present preliminary results of an ongoing study, obtained using a simple toy model created to test the hypothesis that a wind-like expansion of ...
Context. The microquasar Cygnus X-3 was detected at high energies by the gamma-ray space telescopes AGILE and Fermi. The gamma-ray emission is transient, modulated with the orbital period and seems related to major radio flares, i.e. to the relativistic jet. The GeV gamma-ray flux can be substantially attenuated by internal absorption with the ambient X-rays. Aims: We examine quantitatively the ...
Context: .Recently, much attention has been paid to the magnetic coupling (MC) process, which is supported by the very high emissivity indexes observed in Seyfert 1 galaxy MCG-6-30-15 and GBHC XTE J1650-500. But the rotational energy transferred from a black hole is simply assumed to be radiated away from the surrounding accretion disk in the black-body ...
This dissertation presents research on two low mass X-ray binaries. The eclipsing low-mass X-ray binary 4U 1822-371 is the prototypical accretion disk corona (ADC) system. We have obtained new time-resolved UV spectroscopy with the ACS/SBC on the Hubble Space Telescope and new V- and J-band photometry with the 1.3-m SMARTS telescope at ...
We propose a physical model of the Cygnus X-2 like Z-track sources: GX 340+0, GX 5-1 and Cygnus X-2 based on the results of applying a particular emission model for low mass X-ray binaries to high quality Rossi-XTE data on the sources. In this emission model the Comptonizing Accretion Disk Corona is very extended, and the evidence for ...
The eclipsing low-mass X-ray binary 4U 1822-371 is the ideal system in which to observe hot accretion and the effects of strong irradiation. Its orbital period is 5.57~hr and its orbital inclination is high enough that flux from the neutron star is blocked by the edge-on accretion disk in the system. Because the neutron star is hidden ...
We consider axisymmetric viscous accretion flows where a fraction of of the viscously dissipated energy is stored in the accreting gas as entropy and a fraction 1 - f is radiated. Assuming alpha-viscosity we obtain a two-parameter family of self-similar solutions. Very few such exact self-consistent solutions are known for viscous differentially rotating ...
We analyze the RXTE observations of the 2009 outburst of H~1743-322, as well as the observations of the previous five outbursts for comparison. The hardness-intensity diagram (HID) shows a complete counter-clockwise q-track for the 2009 outburst and, interestingly, the track falls in} between a huge one in 2003, with a complete transition to high/soft state, and that of} the failed outburst in ...
To understand the origin of hard X-ray emissions from black-hole X-ray binaries during their low/hard states, we calculate the X-ray spectra of black-hole accretion flow for the following three configurations of hot and cool media: (a) an inner hot-flow and a cool outer disk (inner hot-flow model), (b) a cool disk sandwiched by ...
We identify an accretion disk atmosphere and corona from the high resolution X-ray spectrum of Hercules X-1, and we determine its detailed physical properties. More than two dozen recombination emission lines (from Fe XXVI at 1.78 A to N VI at 29.08 A) and Fe K-alpha, K-beta fluorescence lines were detected in a 50 ks observation with ...
We present a unified model for the formation of jets in X-ray binaries and active galactic nuclei. It has been previously shown that the dividing line between FR I and FR II galaxies in luminosity occurs at the same luminosity as the dividing line between gas-pressure and radiation-pressure dominated disks. We combine past results showing that the scale heights for the ...
We present the results of three-dimensional global magnetohydrodynamic simulations of the Parker-shearing instability in a differentially rotating torus initially threaded by toroidal magnetic fields. An equilibrium model of a magnetized torus is adopted as an initial condition. When beta0=Pgas&solm0;Pmag approximately 1 at the initial state, magnetic flux buoyantly escapes from the ...
Jul 20, 2009... protoplanetary disks, radiative transfer, T-TAURI DISKS, ACCRETION DISKS, YOUNG OBJECTS, CIRCUMSTELLAR DISKS, STARS, GROWTH, EARTH, DUST ...
... studies to, eg, measure inner disk truncation radii, probe the nature of the disk accretion process, and chart the evolution in the gas content of disks. ...
DTIC Science & Technology
The purpose of the two-day Workshop on Physics of Accretion Disks Around Compact and Young Stars was to bring together workers on accretion disks in the western Gulf region (Texas and Louisiana). Part 2 presents the workshop program, a list of poster pres...
The main physical phenomena which occur on accretion disks, are discussed. A numerical simulation of a three dimensional accretion disk model around a white dwarf in a binary system composed of two equal mass stars is developed. The smoothed particle hydr...
With the discovery that Alfven waves can be strongly unstable in a magnetized accretion disk, it can be expected to explain the turbulence necessary to drive accretion in these disks. The instability of non-axisymmetric Alfven waves is studied using analy...
Geometrically thin, optically thick, turbulent accretion disks are believed to surround many stars. Some of them are the compact components of close binaries, while the others are throught to be T Tauri stars. These accretion disks must be magnetized obje...
The influence of accretion disk instabilities on the UV fluxes of Seyfert 1 galaxies was studied. The observed characteristic timescales of variability are consistent with the interpretation that most of the UV radiation originates in an accretion disk, a...
The astrophysical importance of the new class of theoretical models for accretion disks concentrating mainly on the applications to active galactic nuclei are discussed. The slim accretion disks model describes several important astrophysical processes wh...
We examine the role of the accretion disk in the steady-burning white dwarf model for supersoft sources. The accretion luminosity of the disk is quite small compared to the nuclear burning luminosity of the central source. Thus, in contrast to standard ac...
Mar 12, 2005 ... Accretion Disk Simulation Credit: Michael Owen, John Blondin ... Such accretion disks power bright x-ray sources within our own galaxy. ...
The turning point in the relation between the X-ray photon index and the Eddington Ratio for AGN that was recently revealed by Constantin et al. (2009) and Gu & Cao (2009), provides new stimulus for investigating: 1) the role of accretion in powering the ambiguous low luminosity AGN and 2) the proposed analogy between accretion onto supermassive and ...
Nov 9, 2003 ... Consequently accretion disks have fundamental roles in the formation of planets, stars and compact objects, and are the engines driving the ...
... Understanding of accretion disks, accretion flows, X-ray induced winds, compact obect evolution are all in a primitive state. ...
Material falling (accreting) onto a black hole in a binary system, or at the center of a galaxy, forms an accretion disk about the event horizon, with the inner ...
... unique opportunities to study the details of the accretion flow in the cases of normal white dwarfs with accretion disks and magnetic white dwarfs. ...
Radial oscillations resulting from axisymmetric perturbations in viscous accretion disks surrounding
The effect of the differential rotation of the disk of the galaxy on magnetic field which penetrates
How are accretion disks in Seyfert Galaxies oriented relative to the disk of the spiral galaxy which hosts them? This angle, ?, serves as a link between the innermost workings of the black hole plus fueling accretion disk and the larger galaxy, either as the memory of the activity-provoking ...
Recent observations of partial X-ray eclipses from 4U 1822-37 have shown that the central X-ray source in this system is diffused by a large Compton-thick accretion disk corona (ADC). We show that another binary, 4U-2129+47, also displays a partial eclipse and contains an ADC. The possible origin of an ADC is discussed and simple ...
The spectral evolution of accretion disks in X-ray binaries containing black holes is studied, based
The standard model of an accretion disk is considered. The temperature in the inner region is computed. It is assumed that the radiated power derives from comptonized photons, produced in a homogeneous single temperature plasma, supported by radiation pre...
Jan 22, 2011 ... Title: The Production of Jets From Magnetized Accretion Disks: Simulation of the Blandford-Payne Mechanism. Authors: Meier, D. ...
Jan 22, 2011 ... Title: The Production of Jets From Magnetic Accretion Disks: Simulation of the Blandford-Payne Mechanism. Authors: Meier, David L. ...
of a collimated jet ejected from the center of the accretion disk. The jet velocity is a strong function of the strength of the initial magnetic field: ...
The standard model for accretion disks (e.g., Pringle, 1981; Lin and Papaloizou, 1985) parameterizes
Feb 23, 2004 ... "Accretion disks are known to flow around many objects in the universe ... Under normal conditions, accretion disks appear far too minute to ...
Jan 31, 2005 ... KERRBB is a multi-temperature blackbody model for a thin, steady state, general relativistic accretion disk around a Kerr black hole. ...
The thesis consists of an introduction and summary, and five research papers. The introduction and summary provides the background in accretion disk physics and magnetohydrodynamics. The research papers describe numerical studies of magnetohydrodynamical ...
First � Previous � Next � Last � Index � Home � Text. Long-term Periodicities and Accretion Disks. Slide 4 of 22.
Jan 22, 2010 ... Many astrophysical objects, including neutron stars and accretion disks, are powered by a combination of very strong magnetic fields and ...
... Title : Evidence for Residual Material in Accretion Disk Gaps: CO Fundamental Emission from the T Tauri Spectroscopic Binary DQ Tauri. ...
Jun 11, 2010 ... Relativistic Illumination Law from Accretion Disks ... Relativistic Iron Fluorescent Line from Accretion Disks ...
Quasar Jets and Accretion Disks. Questions: " Does the most compact optical emission from an AGN come from an accretion disk or from a relativistic jet? ...
Binary Black Holes, Accretion Disks and Relativistic. Jets: Photocenters of Nearby AGN and Quasars. Principal Investigator: Ann E. Wehrle (Interferometry ...
Dec 19, 1999 ... Here gas from a blue giant star is shown being stripped away into an accretion disk around its compact binary companion. ...
Sep 4, 1998 ... In the case of a HMXB with a large ( $\\mathrel{\\hbox{\\rlap{\\hbox{\\lower4pt\\ ) magnetic field the accretion disk cannot extend all the way down to ...
We present Suzaku broad-band observational results on the Galactic black-hole binary Cygnus X-1. The source was observed for 17 ks with Suzaku in 2005 October, while it was in a low/hard state with a 0.7-300 keV luminosity of 4.6 x 10^37 erg/s. Spectra of the X-ray Imaging Spectrometer (XIS) and the Hard X-ray Detector (HXD) were clearly detected over 0.7-400 keV, and reproduced successfully ...
The black-hole binary Cygnus X-1 was observed for 17ks with the Suzaku X-ray observatory in 2005 October, while it was in a low/hard state with a 0.7-300keV luminosity of 4.6�1037ergs-1. The XIS and HXD spectra, spanning 0.7--400keV, were reproduced successfully, incorporating a cool accretion disk and a hot Comptonizing corona. The ...
Accretion disks around young stars produce excess infrared continuum associated with the disk and excess optical and ultraviolet continua associated with the boundary layer or 'hot spot' as material falls from the disk onto the stellar photosphere. When w...
Based on previous works on black hole accretion disks, I continue to explore the disk dynamics using the finite difference method to solve the highly nonlinear problem of time-dependent alpha disk equations. Here a radially zoned model is used to develop ...
Calculations of the velocity field in an accretion disk show that matter may flow in the disk not only toward but also away from the central object. The rates of flow are determined, and the geometry of hydrodynamic motions in nonstationary disks is discussed.
Equations are derived to describe the accretion disk in the field of a rotating black hole for an arbitrary angle between the plane of the disk and the rotation axis of the black hole. The central zone of the disk will be aligned with the equatorial plane of the black hole.
A central dogma of X-ray astronomy is that luminous X-ray emission is a universal property of efficiently accreting supermassive black holes. One interesting challenge to this idea has come from the quasar PHL 1811 which appears to be intrinsically X-ray weak and also has distinctive emission-line properties. We propose to observe a sample of eight SDSS quasars, selected to ...
The presence of alpha-viscosity in the atmospheres of accretion discs is investigated. It results in the existence of coronae and/or winds. When discs are illuminated by the central X-ray sources, the mass loss may be a significant fraction of the total m...
Planets form inside protostellar disks in a dead zone where the electrical resistivity of the gas is
