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. ...
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do not have accretion disks. Optical spectra are the only way that we can .... inner accretion disks) confirms the asymmetrical distribution of such stars ...
Too hot accretion disks in ULX and superluminal jet sources ... Standard accretion disk around Kerr black hole can explain the hard disk spectra? ...
Spectra of accretion disks in active galactic nuclei & X-ray binaries ... and clean probe of accretion disks and black hole physics in most generic AGN! ...
We consider the structure and emission spectra of nonthermal accretion disks around both strongly and weakly magnetized neutron stars. Such disks may be dissipating their gravitational binding energy and transferring their angular momentum via semicontinu...
National Technical Information Service (NTIS)
Spectra of accretion disks hypothesized to produce the strong optical and ultraviolet flux in quasars and active galactic nuclei were calculated. The spectrum of radiation leaving the disk surface is described by non-LTE stellar atmospheres with high effe...
X-ray illuminated accretion disks. We show how the most relevant atomic features in the spectra depend on the assumed properties of the irradiated gas. ...
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
E-print Network
In this paper, we study the physical properties and characteristics of matter forming thin accretion disks in static and spherically symmetric wormhole spacetimes. In particular, the time averaged energy flux, the disk temperature, and the emission spectra of the accretion ...
Energy Citations Database
Nov 9, 2003... are too small to resolve directly, therefore we intend to use maximum entropy tomography techniques to spatially resolve disk spectra. ...
Thermal radiation from an accretion disk is a promising explanation for the optical-ultraviolet bump noted in the spectra of active galactic nuclei. However, the expected polarization of radiation from a standard thin disk conflicts with observation. The polarization of light emitted by a thin ...
The thermal emission of accretion disks in Active Galactic Nuclei (AGN) is examined. Medium broadband AGN spectra are shown in order to explain the emission mechanism proposed. Basic behaviors from radiation theory and from hydrodynamics of importance for...
We review the empirical constraints on accretion disk models of stellar-mass black holes based on recent multiwavelength observational results. In addition to time-averaged emission spectra, the time evolutions of the intensity and spectrum provide critic...
The importance of simultaneous IUE and Voyager observations of luminous accretion disk systems is shown. The composite spectra of SS Cyg, VW Hyi, CPD-48 1577, and V3895 Sgr show the changes which occur in the continuum flux distributions from 3200 A down ...
The dwarf nova SS Cygni was observed by IUE. The UV low resolution spectra show clear differences in the behavior of the accretion disk in quiescence and in outburst. A steady-state disk model can almost fit the continuum of the outburst spectra, while it...
Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework of the standard optically thick accretion disk in the Schwarzschild metric. On the other hand, ...
Based on a new estimation of their thickness, the global properties of relativistic slim accretion disks are investigated in this work. The resulting emergent spectra are calculated using the relativistic ray-tracing method, in which we neglect the self-irradiation of the accretion disk. The ...
NASA Astrophysics Data System (ADS)
accretion disks in the western Gulf region (Texas and Louisiana). Accretion ... protostellar disks are believed to be accretion disks associated with young, ...
Theory and Modelling Research in the LHEA - Research Topics. Low Mass X-ray Binaries -- Accretion Disk Corona Radiative Transfer � Synthetic X-ray Spectra ...
Feb 9, 2006 ... We recommend keeping this parameter fixed at log(alpha)=-1 or -2, the values for which the spectra were tabulated. ...
resolved spectra of the accretion disk and gas stream of the nova-like variable UX Ursae Majoris." Mon. Notices Roy. Astron. Soc. 298, 1079. ...
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 proton heating, ...
Slim-disk models describe advective accretion flows at high luminosities, while reducing to the standard thin disk form in the low luminosity limit. We have developed a new spectral model, slimbb, within the framework of XSPEC, which describes fully relativistic slim-disk accretion and includes ...
Fully self consistent calculations of the spectra emitted by active galactic nuclei accretion disks are presented. The inner, radiation dominated regions of standard, alpha disks are treated. Incoherent Compton scattering and emission/absorption of radiation by hydrogen and helium are included in computing the ...
The line profiles and relative fluxes of the emission lines in the quiescent spectra of cataclysmic variables contain information about the physical state of the material in the accretion disks around the white dwarfs. Several physical and phenomenological models for the emission line regions are discussed, and the resulting emission ...
Observations of T Tauri stars and young brown dwarfs suggest that the accretion rates of their disks
NASA Technical Reports Server (NTRS)
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
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 ...
Context. The Galactic microquasar SS 433 is very luminous and ejects opposite jets at approximately one quarter the speed of light. It is regarded as a super-Eddington accretor but until recently there were no observations of accretion. Aims: We present an analysis of spectroscopic optical data obtained before and during a major flare, which yield in H? unambiguous evidence ...
dashed lines in Fig. 1 show simple disk spectra for the same values of M, MWD, .... LWD _ 1.5 ? l038 ergs s-1. The parameters for this solution ...
We study the power spectra of the variability of seven intermediate polars containing magnetized asynchronous accreting white dwarfs, XSS J00564+4548, IGR J00234+6141, DO Dra, V1223 Sgr, IGR J15094-6649, IGR J16500-3307 and IGR J17195-4100, in the optical band and demonstrate that their variability can be well described by a model based on fluctuations ...
the disk --- either entering the jet directly (the #12; BLR Accretion Disk ECC RSy ECD SSC e e + Sy FIGURE 1. Illustration of the model geometry and the relevant fl radiation mechanisms for leptonic jet models. ECD is the height of the blob above the accretion disk. The ECD spectrum can exhibit ...
Stellar black-hole candidates and active galactic nuclei are believed to contain accretion disks around black holes. Their X-ray variability is characterized by power spectra with a power law dependence on the variability frequency. The power slope beta is in the range between 1 and 2 and its most typical value is around 1.5. Mineshige ...
The observational appearance of a protostellar accretion disk has been calculated analytically by assuming a thin, thermally emitting disk with an unspecified power-law temperature gradient. The disk is assumed to have both a maximum and a minimum radius. The analytical spectrum is compared with data from the Rho ...
Understanding boundary layer heating is crucial in determining the thermal structure of the accreted envelope of a prenova white dwarf. The matched asymptotic expansion method was used to solve consistently for the structure of accretion disks transferring matter onto rotating white dwarfs. The fraction of ...
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, ...
An analytic approximation of the radiation spectra emitted from the accretion disks of hypothesized supermassive black holes at the centers of quasars and active galactic nuclei is defined. Stellar atmosphere surface gravity and temperature are assumed for every point on the disk surface. Known stellar ...
A simple model of the boundary layer and accretion disk wind of dwarf novae in outburst is briefly described and applied to the Chandra Low Energy Transmission Grating spectra of WZ Sge and SS Cyg in outburst.
DOE Information Bridge
Classical T Tauri stars offer a unique window into star+disk systems that are still in the accretion/outflow phase yet are no longer surrounded by an opaque circumstellar envelope. These objects hold the key to understanding how magnetospheric accretion occurs, how accretion powers outflows, and what the physical ...
The spectra of dwarf novae show broad absorption lines in outburst and strong emission lines during the quiescent state. Simplified calculations are presented for idealized disk models that demonstrate that these features can be attributed to radiative properties of accretion disks. Using these models, it is shown ...
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 ...
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
The authors present a model for the high-low state transition of the X-ray Nova GS 1124-68 (Nova Muscae 1991) observed by Ginga. The model consists of an advection-dominated accretion flow (ADAF) near the central black hole surrounded by a thin accretion disk. During the rise phase of the outburst, as the mass ...
The (U-B), (B-V) and (V-R) colour indexes from accretion disks, and sources with power-law spectra, are calculated. They take into account interstellar extinction, in detail. Results are given on two-colour diagrams (U-B)-(B-V) and (B-V)-(V-R). Applications to Nova Vul 1988 and A0620-00 are discussed shortly.
Active galactic nuclei (AGN) accretion disk spectra were calculated using non-LTE stellar atmosphere models for Kerr and Schwarzschild geometries. It is found that the Lyman limit absorption edge, probably the most conclusive observational evidence for th...
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, ...
Sep 27, 2002 ... Accretion Disk Simulation ... Instead, the graphic shows spiral shock waves in a three dimensional simulation of an accretion disk -- material ...
Black holes are most often detected by the radiation produced when they gravitationally pull in surrounding gas, in a process called accretion. The efficiency with which the hot gas radiates its thermal energy strongly influences the geometry and dynamics of the accretion flow. Both radiatively efficient thin disks and radiatively ...
We present fully self-consistent calculations of the spectra emitted by accretion disks in active galactic nuclei. We treat the inner, radiation-pressure-dominated regions of standard alpha-disks. Incoherent Compton scattering and emission/absorption of radiation by hydrogen and helium are included in compting the ...
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 ...
Quasars are thought to be powered by supermassive black holes accreting surrounding gas. Central to this picture is a putative accretion disk which is believed to be the source of the majority of the radiative output. It is well known, however, that the most extensively studied disk model-an optically thick ...
We present an archival study of ultraviolet spectra of the X-ray binary LMC X-4 obtained with the IUE satellite. We fit these spectra with models that incorporate the X-ray heating of the O star and accretion disk. A systematic analysis of the UV continuum confirms the general picture of an O star that fills its ...
We present our code for the calculation of the 1D structure and synthetic spectra of accretion disks. The code is an extension of the well-tested stellar atmosphere code PHOENIX and is therefore capable of including large lists of atomic and molecular lines as well as a large set of dust species. We assume the standard ...
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 corona, atmospheric ...
We calculate upper bounds on the inner radii of geometrically thin accretion disks in galactic black hole systems by relating their rapid variability properties to those of neutron stars. We infer that the inner disk radii do not exhibit large excursions between different spectral states, in contrast with the concept that the ...
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 ...
We explore the effect of the stellar magnetic field on the spectrum of the disk by comparing synthesized disk spectra to the observed ultraviolet spectrum of the well-studied DQ Her binary GK Per. We use the parameterized disk-magnetosphere interaction models of Miller and Lamb to calculate the radius of the inner ...
We study the accreting white dwarfs (WDs) and accretion disks in Cataclysmic Variables (CVs) by carrying out a systematic analysis of the FUSE spectra of galactic CVs. Using the codes TLUSTY, SYNSPEC and BINSYSN, we generate synthetic spectra of WDs, and accretion ...
As several authors in the past, we calculate optically thick but geometrically thin (and slim) accretion disk models and perform a ray-tracing of photons in the Kerr geometry to calculate the observed disk continuum spectra. Previously, it was common practice to ray-trace photons assuming that they are emitted from ...
The warped spacetime near black holes is one of the most exotic observable environments in the Universe. X-ray spectra from active galaxies obtained with the current generation of X-ray observatories reveal line emission that is modified by both special relativistic and general relativistic effects. The interpretation is that we are witnessing X-ray irradiated matter orbiting ...
The standard spectral model for analyzing the soft component of thermal emission from a thin accretion disk around a black hole is the multi-temperature blackbody (MTB) model. The widely used implementation of this model, which is known as ``diskbb,'' assumes nonzero torque at the inner edge of the accretion disk. ...
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, ...
In this work, we consider the possibility of observationally testing Ho?ava gravity by using the accretion disk properties around slowly rotating black holes of the Kehagias-Sfetsos (KS) solution in asymptotically flat spacetimes. The energy flux, temperature distribution, the emission spectrum as well as the energy conversion efficiency are obtained, and ...
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 nonthermal source which produces the ...
AG Dra is a symbiotic variable bearing a number of similarities to the suspected emitting components in RS Oph among which are an irradiated red giant mass donor, metal poor, similarly long orbital periods, a hot accreting white dwarf irradiating an optically thick bright accretion disk. Both objects have been counted among the yellow ...
Consideration is given to the effects of thermal and nonthermal electron-positron pair production upon the structure of two-temperature accretion disks and upon the two-temperature criterion in quasi-spherical accretion flows, by balancing pair creation with annihilation and inflow. It is found that thermal pair creation is unimportant ...
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 spectrum of Gamma rays from the decay of Pi dey is sensitive to the ... X- Ray Reflected Spectra from Accretion Disk Models. II. Diagnostic Tools for X-Ray ... This study demonstrates the ability of the model to generate recurrent 3D ...
Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40
Our very-first high resolution spectra of SV Cen close binary system obtained in the H? line reveal its absorption and emmision components, changing with orbital phase. An accretion disk surrounding the component eclipsed at the primary minimum is the most plausible explanation of this complex structure.
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 ...
This work led to the development of code for fitting models to data, and to an understanding of the nature of the models which enabled a more rapid search of 'parameter space' of optimal fits to spectral data sets. The code was used to find optimal fits t...
... Presumably, ULXs are X-ray binaries with possible maximum stellar-size black holes; ~40 M� black holes theoretically possible (Fryer 1999)
The Lyman edge region in the spectra of 11 high-redshift quasars is studied using data designed to detect broadened Lyman edge absorption predicted by thermal models of the 'big blue bump' continuum component, especially thin accretion disks. Three objects have broadened, partial edges near the systemic redshifts, as ...
A possible accretion model associated with the ionization instability of quasar disks is proposed to
Ultraviolet resonance lines appear to be powerful tools for diagnostics and study of the outflows from cataclysmic variable stars. The origin of these winds and their geometry are not known at present. In order to compare observed lines from the IUE database with synthetic line profiles from accretion disk winds, we have developed a numerical radiation ...
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 ...
We present Suzaku and XMM observations of the high-mass X-ray pulsar LMC X-4 at different phases in its superorbital cycle, which is due to the precession of a warped accretion disk. The superorbital period and phase for each observation is determined accurately using RXTE ASM data. At all superorbital phases, the broadband X-ray ...
Optical and IR spectroscopy data on the T Tauri star FU Ori obtained with instrumentation at Kitt Peak and the Mt. Hopkins Multiple Mirror telescope were examined for double peaks predicted by a disk accretion model. The data, collected in January 1986, were used to calculate a mean extinction curve and optical spectra. Comparison of ...
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 ...
We develop numerical models of accretions disks in cataclysmic variables (CVs), including and emphasizing the boundary layer region where the accretion disk meets the accreting white dwarf. We confine ourselves to solutions where the boundary layer region is vertically optically thick, and find ...
I present H- and K-band light curves of the dwarf nova cataclysmic variable (CV), IP Peg, and the novalike CV, RW Tri, and an H-band light curve of the novalike CV, SW Sex. All three systems showed contributions from the late-type secondary star and the accretion disk, including a primary eclipse of the accretion ...
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, ...
We present a model of accretion disk where the disk luminosity is entirely due to the reprocessing of hard radiation impinging on the disk. The hard radiation itself is emitted by a hot point source above the disk, that could be physically realized by a strong shock terminating an aborted jet. ...
The formation and evolution of an accretion disk formed during the collapse of a rotating cloud core
Recent work on the X-ray spectra of Seyfert galaxies has shown the presence of a reflection component due to the hard X-ray continuum scattering from, and causing fluorescence by, cold matter. The strength of the reflection spectrum is usually consistent with the hard X-rays being emitted above a flat accretion disk. In this paper we ...
Multiwavelength spectra of the long-period Algol AU Mon (P = 11.1 days) have been studied to determine the properties of the accretion structures in the binary. The spectra were collected with the 0.9m Coude Feed Telescope at KPNO and also with the 9m Hobby-Eberly Telescope high resolution spectrograph. A total of 50 ...
We propose to obtain mid-IR spectra using IRS on board Spitzer of four ~5 Myr old stars in the Orion OB1b association, which show indications of an advanced degree of dust evolution in their disks, and for which the ground-based observations suggest they are in the critical phase just prior to the opening of gaps in their disks. Our ...
We analyze narrow-band eclipse light curves of the nova-like cataclysmic variable UX UMa, obtained from low-resolution spectra spanning lambda lambda 3600-9800 A . The light curves for narrow bands in the continuum as well as those for individual spectral lines are treated independently, and are used to construct images of the accretion ...
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...
We perform detailed radiative transfer modeling of the emission expected from magnetic flares in Active Galactic Nuclei (AGN). We assume a compact flare source above the accretion disk surrounding a supermassive black hole. The source is supposed to be anchored in the disk by magnetic structures and orbits around the center on ...
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 ...
Understanding how disks dissipate is essential to studies of planet formation. However, identifying exactly how dust and gas dissipate is complicated due to the difficulty of finding objects that are clearly in the transition phase of losing their surrounding material. We use Spitzer Infrared Spectrograph (IRS) spectra to examine 35 photometrically ...
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. ...
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...
The inner accretion disk geometry of black hole binaries (BHBs) in transition between the low/hard and high/soft states is important for understanding accretion flow around black holes. In the low/hard state a discrepancy exists over whether the cool, optically thick accretion disk extends ...
We present new models for illuminated accretion disks, their structure and reprocessed emission. We consider the effects of incident X-rays on the surface of an accretion disk by solving simultaneously the equations of radiative transfer, energy balance and ionization equilibrium over a large range of column ...
We present new models for illuminated accretion disks, their structure, and reprocessed emission. We consider the effects of incident X-rays on the surface of an accretion disk by simultaneously solving the equations of radiative transfer, energy balance, and ionization equilibrium over a large range of column ...
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 ...
Classical T Tauri stars undergo magnetospheric accretion, power outflows, and possess the physical and chemical conditions in their disks to give rise to planet formation. Existing high resolution FUV spectra verify that this spectral region offers unique diagnostics of these processes, which have the potential to significantly advance ...
Radiation can play a significant role in the transport of angular momentum from relativistic accretion disks, leading to intrinsically nonlinear systems. This thesis considers what this implies for the non-pulsing x-ray binary systems, particularly with regard to the x-ray bursters. Considerations here are founded on a time-dependent model of a ...
The brane-world description of our universe entails a large extra dimension and a fundamental scale of gravity that might be lower by several orders of magnitude as compared to the Planck scale. An interesting consequence of the brane-world scenario is in the nature of the vacuum solutions of the brane gravitational field equations, with properties quite distinct as compared to the standard ...
We present a new 2D ray-tracing technique for computing the emergent spectra of winds originating from the surfaces of primary star and accretion disk in cataclysmic binaries. By using a highly modular approach, allowing easy modification and extension of the code, we self-consistently solve the pan-chromatic radiative transfer problem ...
We report on a scheme for incorporating vertical radiative energy transport into a fully relativistic, Kerr-metric model of optically thick, advective, transonic alpha disks. Our code couples the radial and vertical equations of the accretion disk. The flux was computed in the diffusion approximation, and convection is included in the ...
Spectra in outburst sources are found to become soft in viscous timescales before going back to hard as in the pre-outburst phase. By using two component accretion disks we show that major characteristics of the spectral evolution can be reproduced. We find that the outburst is possibly caused by a sudden rise in viscosity which ...
Optical spectra of the emission lines in a sample of 6 recent novae (the recurrent novae YY Dor, N LMC 2009, and U Sco, and the He-Ne novae DE Cir, V2672 Oph, and KT Eri) show Balmer lines consisting of a broad pedestal of emission with a narrower superposed central emission component. While the broad pedestal is generally modelled as an expanding equatorial torus, we argue ...
Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework of the standard...
Angular momentum transport by photons is analyzed for thin and thick configurations of steady accretion flows near black holes. The radiative viscosity coefficient is derived accurately from kinetic theory for arbitrary photon spectra. Thin Keplerian disks cannot be supported by radiative viscosity. However, in a quasi-spherical ...
A unified treatment is presented of the two distinct states of vertically thin AGN accretion disks: a cool (about 10 to the 6th K) optically thick solution, and a hot (about 10 to the 9th K) optically thin solution. A generalized formalism and a new radiative cooling equation valid in both regimes are introduced. A new luminosity limit is found at which ...
We present an analysis of the broadband spectra of 4U 1705-44 obtained with Suzaku in 2006-2008 and by BeppoSAX in 2000. The source exhibits two distinct states: the hard state shows emission from 1 to 150 keV, while the soft state is mostly confined to be <40 keV. We model soft-state continuum spectra with two thermal components, one of which is a ...
We have carried out a combined Hubble Space Telescope (HST/GHRS) and Far Ultraviolet Spectroscopic Explorer (FUSE) analysis of the prototype dwarf nova SS Cygni during quiescence. The FUSE and HST spectra were obtained at comparable times after outburst and have matching flux levels where the two spectra overlap. In our synthetic spectral analysis, we have ...
A number of neutron star low-mass X-ray binaries (LMXBs) have recently been discovered to show broad, asymmetric Fe K emission lines in their X-ray spectra. These lines are generally thought to be the most prominent part of a reflection spectrum, originating in the inner part of the accretion disk where strong relativistic effects can ...
The UV spectra of nova-like variables are dominated by emission from the accretion disk, modified by scattering in a wind emanating from the disk. Here, we model the spectra of RW Tri and UX UMa, the only two eclipsing nova-like variables which have been observed with the Hubble Space Telescope ...
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 ...
We have calculated the reflection component of the X-ray spectra of active galactic nuclei (AGN) and shown that they can be significantly modified by the relativistic motion of the accretion flow and various gravitational effects of the central black hole. The absorption edges in the reflection spectra suffer severe energy shifts and ...
Context. We present angle-dependent, broad-band intensity spectra from accretion disks around black holes of 10 M?. In our computations disks are assumed to be slim, which means that the radial advection is taken into account while computing the effective temperature of the disk. Aims: We ...
We present the results of hydrodynamical simulations of the disk photosphere irradiated by strong X-rays produced in the innermost part of the disk of an accreting black hole. As expected, the irradiation heats the photosphere and drives a thermal wind. To apply our results to the well-studied X-ray transient source GRO J1655-40, we ...
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 ...
UV emission in many X-ray binaries is dominated by X-raysreprocessed in the accretion disk. For pulsars illumination ofthe accretion disk by a rotating beam of X-rays should resultin pulsed UV emission lines with Doppler shifts correspondingto projected gas velocities. Simultaneous high time resolutionUV and X-ray ...
The Mira AB system is a nearby (~107 pc) example of a wind accreting binary star system. In this class of system, the wind from a mass-losing red giant star (Mira A) is accreted onto a companion (Mira B), as indicated by an accretion shock signature in spectra at ultraviolet and X-ray wavelengths. Using novel ...
We obtained Hubble Space Telescope far-ultraviolet spectra of the Z Cam-type dwarf nova RX And during the early rise to outburst and the decline from the same outburst. The spectral wavelength range covered was 1149-1435 �. The rise spectrum is dominated by strong, very broad absorption lines, while the decline spectrum has strong, narrower absorption with weak to moderately ...
Galactic accreting compact objects, such as stellar-mass black holes and neutron stars, can give us a unique perspective into the behavior of matter in extreme conditions. However, the exact nature of accretion onto these objects is not yet well understood. X-ray studies provide us with a means to observe the innermost regions around these objects and to ...
Galactic accreting compact objects, such as stellar-mass black holes and neutron stars can give us a unique perspective into the behavior of matter in extreme conditions. However, the exact nature of accretion onto these objects is not yet well understood. X-ray studies provide us with a means to observe the innermost regions around these objects and to ...
AU Mon is a long period (11.113 days) Algol binary system with a stable accretion disk that can be seen in the double-peaked emission in the H-alpha line. We present new modeling of the accretion structures in this system. We have reexamined archival UV data from the IUE telescope spanning 15 years and we have also analyzed H-alpha ...
Hot accretion disks around rotating black holes produce copious amounts of X-rays, ..gamma..-rays and e/sup +/e/sup -/ pairs. These Comptonized models with an energy flux spectral index of the X-ray spectrum approx. 1 are optically thick to ..gamma gamma.. pair production. The resultant high energy spectrum steepens above a few MeV. The few ..gamma..-ray ...
Black hole XRB X-ray variability contains information about the accretion and emission mechanisms in strong gravity, but to unlock this information and understand the very rich phenomenology of X-ray timing properties (band-limited noise, QPOs, low-frequency noise), we need to understand the origin of the variations. For many years it has been assumed that the Lorentzian ...
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. ...
We obtained Hubble STIS spectra of three nova-like variables: V751 Cygni, V380 Oph, and-the only confirmed nova-like variable known to be below the period gap-BK Lyn. In all three systems, the spectra were taken during high optical brightness state, and a luminous accretion disk dominates their far-ultraviolet ...
with Dr. Shoji Kato (ITP & Kyoto Univ)I discuss the transition from an optically thick cool Shakura-Sunyaev disk to anoptically thin hot advection-dominated accretion flow at certain radius whichmight give explanations to the low state spectra of black hole X-ray binaries.The main point in our model is the inclusion of the ...
The disk instability model for dwarf nova eruptions is investigated by computing the spectral development of the accretion disk through a complete limit cycle. Observed stellar spectra are used to model the radiation emitted by optically thick annuli within the disc. The general findings agree with those of Smak ...
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
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 advection dominated ...
Low mass X-ray binaries (LMXBs) are interacting systems in which a neutron star or black hole accretes material from a donor star via an accretion disk. LMXBs provide excellent environments for studying the evolution of compact objects, disk accretion dynamics, and physics in the strong gravity ...
Accretion disks around super-massive black holes are widely believed to be the source of the optical/UV continuum in many classes of active galactic nuclei. We study the relationships between the optical/UV continuum colors and the characteristic disk temperature as inferred from the AGN bolometric luminosity and black hole mass. AGN ...
Low-resolution, ultraviolet spectra of the pre-main-sequence objects Z Canis Majoris, V1057 Cygni, and FU Orionis are presented. Ultraviolet absorption features indicate spectral types of A5 I for FU Ori and F5 I for Z CMa. These results are in reasonable agreement with predictions of simple accretion disk models. The lack of ...
Time-resolved spectroscopy covering half an orbit and one eclipse during an outburst of the dwarf nova IP Peg are presented and compared with quiescent data. The outburst spectra show strong Balmer and He II 4686 A emission lines that are atypical of outbursting dwarf novae. Double-peaked velocity profiles and rotational distortions during eclipse show that the lines arise ...
abridged: We use XSCORT, together with the hydrodynamic accretion disc wind simulation from Proga & Kallman (2004), to calculate the impact that the accretion disk wind has on the X-ray spectrum from a 1E8 solar mass black hole Active Galactic Nuclei (AGN) accreting at 0.5 L/L_Edd. The properties of the ...
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 ...
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: ...
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 ...
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 ...
Jan 22, 2010 ... Many astrophysical objects, including neutron stars and accretion disks, are powered by a combination of very strong magnetic fields and ...
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? ...
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 ...
