The spectral evolution of accretion disks in X-ray binaries containing black holes is studied, based

... Title : Evidence for Residual Material in Accretion Disk Gaps: CO Fundamental Emission from the T Tauri Spectroscopic Binary DQ Tauri. ...

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? ...

The broad line profiles of active galaxies are consistent with emission from the surface of an accretion disk ionized by an ultraviolet continuum emitted from a linear or point source of continuum above the disk. If the point source is offset from the axi...

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 ...

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...

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 aim to monitor T Tauri star disk emission features and jet outflow morphologies to determine how these features vary with disk accretion rate, and how and when the outflow responds to major accretion events. Young stars are surrounded by circumstellar disks through which ...

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...

An effort is made to observationally constrain accretion disks on the basis of light curves from the eclipsing cataclysmic variable UX Ursae Majoris, reconstructing the spectral energy distribution across the face of an accretion disk. The spectral resolution obtained suffices to reveal not only the radial ...

accretion disks in the western Gulf region (Texas and Louisiana). Accretion ... protostellar disks are believed to be accretion disks associated with young, ...

The short-period Algol system TZ Eri was observed spectroscopically during 10 eclipses in order to study the accretion disk surrounding the primary star. It is shown that this disk belongs to the class of transient accretion disks which are produced by a collision of the gas stream with the ...

The broad line profiles of active galaxies are consistent with emission from the surface of an accretion disk ionized by an ultraviolet continuum emitted from a linear or point source of continuum above the disk. If the point source is offset from the axis of the disk, then the line peak is ...

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 ...

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 ...

The photoionization of extended narrow-line regions in Seyfert galaxies by the radiation produced in a thick accretion disk is studied. The emission-line spectrum is calculated for a range of black hole masses, varying the values of the ionization parameter and the disk size. It is found that models with a million ...

High resolution infrared spectroscopy is a very valuable tool for the study of the formation of low mass and very low mass stars. At the stage in which these objects are already visible, they still undergo strong mass accretion and mass loss processes. Many of the features observed on these stars can be explained by the magnetospheric accretion model, in ...

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...

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

We have found an isolated polar disk galaxy in what appears to be a cosmological wall situated between two voids. This void galaxy is unique as its polar disk was discovered serendipitously in an H I survey of SDSS void galaxies, with no optical counterpart to the H I polar disk. Yet the H I mass in the disk is ...

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 ...

The results of a grid of non-Local thermodynamic equilibrium (LTE) accretion disk models are presented. These models were computed by a program which calculates the radiative transfer at positions in an accretion disk characterized by a local temperature and midplane density. The models cover a range of ...

The results of a grid of non-Local thermodynamic equilibrium (LTE) accretion disk models are presented. These models were computed by a program which calculates the radiative transfer at positions in an accretion disk characterized by a local temperature and midplane density. The models cover a range of ...

The observed profiles of the Fe K alpha line in case of some Active Galactic Nuclei (AGN) show certain variations. In this paper we propose a model of disk emissivity variability to explain the observed Fe K alpha line profiles. The disk emission was analyzed using the ray-tracing method in Kerr metric, assuming a ...

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, ...

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 have studied the dependence of the profiles of molecular abundances and line emission on the accretion flow in the hot ($\\ga 100$K) inner region of protoplanetary disks. The gas-phase reactions initiated by evaporation of the ice mantle on dust grains are calculated along the accretion flow. We focus on ...

Within the framework of unsaturated Compton disk accretion onto a supermassive black hole as a model

In this paper we report 2007-2009 multicolour observations of the dwarf nova AH Her aiming to test the steady-state model for accretion disk emission.

Dec 31, 2008 ... A particularly powerful diagnostic is possible with very rapidly rotating black holes: the accretion disk capable of producing line emission ...

Dec 31, 2008... non-rotating accretion disk illuminated by an isotropic source of ... a hardening above ~ 10 keV and a Ka fluorescent emission line of ...

How does the Soft component change during the spectral evolution? Does the Rin of the accretion disk change? Is there any non-thermal emission component in ...

Dec 10, 2009 ... "Suzaku's sensitivity to iron emission lines and its ability to measure the ... confirms the presence of low-density accretion flow in these systems. ...

The heating and radiative cooling of steady-state viscous accretion disks in close binary systems are studied. It is shown that the temperatures of the outer regions of disks do not fall below approx.6000 K over a wide range of conditions. Depending upon the mass accretion rate, the outer parts of ...

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 ...

Spiral shocks have been discovered in hot accretion disks in dwarf novae during outbursts, using Doppler maps of HeI and Balmer emission lines. Here, we present the eclipse light curves of these lines and we simulate the parameters that affect dilution of the spiral shock light by the ambient symmetric disk ...

The exchange of angular momentum between accreting matter and the magnetosphere of a neutron star is studied as a possible explanation for the soft X-ray emission of X-ray pulsars. The flux of soft X-radiation from Her X-1 may be related to dissipation of rotational energy of accreting matter into a layer of the ...

Emission-line profiles of several cataclysmic variables have been observed through eclipse, and they do not show strong evidence for the rotational signature that is characteristic of an accretion disk. The lines appear to be formed in material that has some rotation with respect to the white dwarf, but that also has a substantial ...

The black-hole/accretion-disk model proposed to explain the high observed luminosities of AGN is discussed, reviewing the results of recent observational and theoretical investigations. The derivation of the governing equations for black holes and thick or thin disks is outlined; numerical predictions are presented in tables and graphs; and the ...

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 ...

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 ...

We studied the disk emission component hidden in the single-peaked broad emission lines (BELs) of active galactic nuclei (AGN) using a two-component model. We assumed that the broad lines are formed in an accretion disk plus a surrounding non-disk region, with isotropic ...

suggest that the gaseous disks becomes optically thick radially once the accretion rate drops below a few times 10W8 Ma yr-l. Its vertical scale height is ...

Observationally, some active galactic nuclei show soft x-ray excess which suggests that spectrum deviates from black body. Attempts in calculating the emission spectrum for optically thick disk were made. Most investigations to date were made by adopting ...

A Primer on Circums. �'Primordial' disk: Accretion; Star+optically- thi k di k. i i f. & d t E thick disk emission from gas & dust. Excess ...

. Magnetic materials. EMF. Faraday's law and the dynamo principle. Inductance and transformers. P.1.2b, accretion disks: disk temperature and spectral response, aspects of nuclear burning, supernovae

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 ...

The observed iron K{alpha} fluorescence lines in Seyfert I galaxies provide strong evidence for an accretion disk near a supermassive black hole as a source of the line emission. These lines serve as powerful probes for examining the structure of inner regions of accretion disks. Previous ...

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 ...

A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles that are well-fitted by a relativistic accretion disk model. We develop a Monte Carlo code to compute the linear polarization of a double peaked broad emission line arising from Thomson scattering. A Keplerian ...

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 ...

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 ...

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 ...

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 have found that two members of the TW Hydrae association, TW Hydrae and Hen 3-600A, are still actively accreting, based on the ballistic infall signature of their broad Halpha emission profiles. We present the first quantitative analysis of accretion in these objects and conclude that the same accretion ...

Accretion disks are widely believed to be the source of the optical/UV continuum in active galactic nuclei. However, continuum colors of AGN do not track disk temperatures as expected, remaining constant or becoming redder with higher disk temperature (Bonning et al. 2007, ApJ 659, 211). Here we study the ...

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 ...

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 ...

We propose an eclipsing light-curve diagnosis for black-hole accretion flows. When emission from an inner accretion disk around a black hole is occulted by a companion star, the observed light curve becomes asymmetric at ingress and egress on a time scale of 0.1-1seconds. This light-curve analysis provides a means ...

Accretion disks are among the most luminous and ubiquitous sources in astrophysics and they have drawn a good deal of attention from the observational and theoretical communities. In this paper, we study the process of matter forming thin accretion disks around black hole solutions in the context of the brane-world ...

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 first VLBI images of H2O maser emission in the Circinus Galaxy AGN show both an accretion disk and outflow 0.1 to 1 pc from the central engine. The maser traces a warped, edge-on accretion disk between radii of about 0.1 and 0.4 pc that is bound by a 1.3�106 Msolar central mass. The ...

A possible accretion model associated with the ionization instability of quasar disks is proposed to

We propose a 100-ks triggered XMM observation of the accreting millisecond pulsar J1808 in its next outburst to gather strong evidence of the inner disk origin of its broad iron emission line. The accretion disk during short-outburst transients is expected to be truncated both at the inner ...

We calculate the temperature profiles of (thin) accretion disks around rapidly rotating neutron stars (with low surface magnetic fields), taking into account the full effects of general relativity. We then consider a model for the spectrum of the X-ray emission from the disk that is parameterized by the mass ...

Accretion from a disk onto a collapsed, relativistic star--a neutron star or black hole--is the mechanism widely believed to be responsible for the emission from compact X-ray binaries. Because of the extreme spatial resolution required, is not yet possib...

We present near-infrared, H-band (1.45 - 1.85 m) observations of the eclipsing dwarf nova, IP Peg, in quiescence. The light curves are composed of ellipsoidal variations from the late-type secondary star and emission from the accretion disk and the bright spot. The light curves have two eclipses: a primary eclipse of the ...

Approximately half the luminosity of a typical cataclysmic variable may emerge as an optically thick component peaking in the EUV. Observations of this component are important for understanding the energetics and accretion rates of CV's in general, as well as for understanding the physics of the accretion process. The nature of the turbulent ...

Optical spectroscopy of the nova-like variable V1315 Aql shows strong single-peaked emission lines, high-velocity s-waves in the wings of the lines, and two distinct absorption components. In order to explain all the features, I suggest that disk overflow accretion has to be combined with an 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 nonthermal source which produces the ...

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, ...

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 ...

The formation and evolution of an accretion disk formed during the collapse of a rotating cloud core

A thin, energy accumulating alpha-disk which orbits a Kerr black hole is reported. Energy accumulating disks are compared with standard thin disks. In the innermost region, the accumulating disk can be rapidly cooled by means of bremsstrahlung, leading to a rapid energy release in the inner region. In the innermost ...

Hyperaccreting neutron stars or magnetar disks cooled via neutrino emission can be candidates of gamma-ray burst (GRB) central engines. The strong field >=1015-1016 G of a magnetar can play a significant role in affecting the disk properties and even lead to the funnel accretion process. In this paper, we ...

Hyperaccreting neutron stars or magnetar disks cooled via neutrino emission can be candidates of gamma-ray burst (GRB) central engines. The strong field {>=}10{sup 15}-10{sup 16} G of a magnetar can play a significant role in affecting the disk properties and even lead to the funnel accretion process. In ...

Studies of classical T Tauri stars have indicated that the accretion footprint lies in middle to polar latitudes on the star, consistent with theoretical expectations of the funnelled-accretion model. Herbig Ae stars are higher mass analogs of classical T Tauri stars. Their circumstellar disks, disk lifetimes and ...

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 studied the geometry of the inner (AU-scale) circumstellar environment around the Herbig Be star MWC 147. Combining, for the first time, near- (NIR, K band) and mid-infrared (MIR, N band) spectro-interferometry on a Herbig star, our VLTI/MIDI and AMBER data constrain not only the geometry of the brightness distribution, but also the radial temperature distribution in the ...

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...

Whether the existence of cold accretion disks around isolated, magnetized neutron stars might result in a distinct observational signature due to the Compton drag interaction between the electrostatically accelerated changes and the thermal radiation emitted by these disks. The particle dynamics resulting from the combined effects of ...

It is now widely accepted that most galaxies undergo an active phase, during which a central super-massive black hole generates vast radiant luminosities through the gravitational accretion of gas. Winds launched from a rotating accretion disk surrounding the black hole are thought to play a critical role, allowing the ...

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 Roche lobe and is heated by X-rays from the ...

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 ...

Chandra and XMM data have revealed narrow and highly redshifted Fe K emission lines in a handful of AGN. Rapid flux variability and energy shifts of the lines have lead to speculations for their origin ranging from hotspots on the accretion disk to emission from decelerating ejected blobs of gas traveling close to ...

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 our understanding of ...

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 ...

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 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 corona is unaffected by multiple scattering in the ...

We investigate the properties and evolution of accretion tori formed after the coalescence of two compact objects. At these extreme densities and temperatures, the accreting torus is cooled mainly by neutrino emission produced primarily by electron and positron capture on nucleons (?-reactions). We solve for the ...

We show that changes in the orientation of the inner accretion disk of Cygnus X-1 affect the shape of the broad Fe K{alpha} emission line emitted from this object, in such a way that eV-level spectral resolution observations (such as those that will be carried out by the ASTRO-E2 satellite) can be used to analyze the dynamics of the ...

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 expected for thermal ...

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 ...

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...

Too hot accretion disks in ULX and superluminal jet sources ... Standard accretion disk around Kerr black hole can explain the hard disk spectra? ...

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 ...

The Balmer H alpha emission line in the stationary spectrum of SS 433 has a component originating in the wind above the accretion disk. The Doppler motion of this line is a blurred representation of the motion of the compact object accreting. I show how this may be understood in terms of ...

Most black hole binaries show large changes in X-ray luminosity caused primarily by variations in mass accretion rate. An important question for understanding black hole accretion and jet production is whether the inner edge of the accretion disk recedes at low accretion rate. Recently, ...

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 ...

The dynamical and radiative consequences of disk accretion onto magnetic T Tauri stars (TTS) are examined using the Ghosh and Lamb model. It is shown that a prolonged disk accretion phase is compatible with the low rotation rates measured in these stars if they possess a kilogauss strength field that disrupts the ...

The exchange of angular momentum between accreting matter and the magnetosphere of a neutron star is studied as a possible explanation for the soft X-ray emission of X-ray pulsars. The flux of soft X-radiation from Her X-1 may be related to dissipation of rotational energy of accreting matter into a layer of the ...

In this work we present the results from analysis of the H? emission line observed at the primary minimum, at phases in the 0.0138 - 0.0263 range, when the disk was partly eclipsed by the mass losing star. The results indicate that the double peaked emission profile can be explained as being emitted in a large, eccentric ...

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 ...

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 ...

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 ...

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 ...

Recent Spitzer IRAC observations of young stars in Orion and NGC 2264 have shown a strong link between primordial circumstellar disks and stellar rotation. Slow rotators show a larger percentage of stars with excess infrared emission than fast rotators. If stars with massive primordial disks evolve into massive debris ...

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. ...

In the accretion disks of quiescent dwarf novae, Doppler mapping studies reveal that Balmer emission lines increase sharply toward the center of the disk, with surface brightnesses scaling roughly as R exp {minus}3/2 varies as Omega(Kep). Similarly, among chromospherically active stars the H-alpha and Ca II H and K ...

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 ...

Various papers on accretion disks (ADs) and magnetic fields in astrophysics are presented. Individual topics addressed include: relevance of magnetic fields to stars and ADs, nonlinear breakup of the sun's toroidal field, accretion and particle acceleration by spiral shock wages, MHD flows in ADs and jets, slender flux tubes in ADs, ...

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 ...

A subset of Active Galactic Nuclei (AGNs) have broad, double-peaked Balmer emission lines, regarded as the best kinematic evidence for the production of broad lines by the accretion disk. It has been suggested that double-peaked emitters have a weak or non-existent disk-wind, hence offering a direct view of the ...

continuum power laws, emission lines, and a thermal Big Blue Bump (BBB). ..... in the nuclei of galaxies will yield important information on their overall lifetime and on the .... broad Balmer lines may be an outer extension of the accretion disk. ...

Radial velocity studies of accreting binary stars commonly use accretion disk emission lines to determine the radial velocity of the primary star and therefore the mass ratio. These emission-line radial velocity curves are often shifted in phase from the expected motion of the primary. These ...

Jul 22, 2011 ... Ionized relativistic line (relline profile). ? Bulk emission possibly from Fe XXV/XXVI. ? Reflection from accretion disk ~20-100r ...

The present report concerns the following projects 'High energy emission from hot accretion disks from active galactic nuclei'; 'OSSE spectral timing and monitoring observations of Cygnus X- 1'; 'OSSE observations of blazars'; and 'Search for correlated t...

"Gravitaionally Redshifted Emission Implying ann Accretion Disk and Massive Black Hole in the Active Galaxy MCG-6-30-15" Y. Tanaka, K. Nandra, A.C. Fabian, ...

The most energetic phenomena in the universe are systems powered by gravity through accretion. For compact stars such as white dwarfs, neutron stars, and especially black holes, the energy released per unit mass accreted can significantly exceed that released by nuclear reactions. Over the last half century a growing body of observations has revealed a ...

We present Keck Interferometer observations of the three prototypical FU Orionis stars, FU Ori, V1057 Cyg, and V1515 Cyg. With a spatial resolution of a few milliarcseconds and a spectral resolution of ?/?? = 2000, our near-infrared observations spatially resolve gas and dust emission extending from stellocentric radii of ~0.05 AU to several AU. We fit these data with ...

Accretion is a fundamental process which establishes the dynamics of the protoplanetary disk and the final properties of the forming star. In solar-type stars, the star-disk coupling is determined by the magnetic field structure, which is responsible for funneling material from the disk midplane to higher latitudes ...

Accretion is a fundamental process which establishes the dynamics of the protoplanetary disk and the final properties of the forming star. In solar-type stars, the star-disk coupling is determined by the magnetic field structure, which is responsible for funneling material from the disk midplane to higher latitudes ...

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 ...

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 ...

Low-mass X-ray binaries (LMXBs) are systems in which a low-mass companion transfers mass via Roche-lobe overflow onto a black hole (BH) or a weakly magnetized neutron star (NS). It is believed that both the solid surface and the magnetic field of an NS can affect the accretion flow and show some observable effects. Using the disk ...

The observed iron K{alpha} fluorescence lines in Seyfert I galaxies provide strong evidence for an accretion disk near a supermassive black hole as a source of the emission. Here we present an analysis of the geometrical and kinematic properties of the disk based on the extreme frequency shifts of a line profile as ...

A maximum likelihood analysis of the NGC 4258 maser positions and velocities reveals a ~2 ? deviation from Keplerian motion in the projected rotation curve of the high-velocity features, corresponding to a ~9 km s-1, or 0.8%, flattening of the LOS velocities with respect to Keplerian motion over the range of the high-velocity masers. While there are a number of potential explanations for this ...

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 ...

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 Kerr geometry ...

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 higher mass accretion ...

Tidal torques acting on a gaseous accretion disk around a binary black hole can create a gap in the disk near the orbital radius. At late times, when the binary inspiral time scale due to gravitational wave emission becomes shorter than the viscous time scale in the disk, the binary decouples ...

It seems to be a widely accepted opinion that the types of accretion disks (or flows) generally realized in the nuclei of radio galaxies and in further lower mass-accretion rate nuclei are inner, hot, optically thin, radiatively inefficient accretion flows (RIAFs) surrounded by outer, cool, optically thick, ...

The formation of low mass stars takes place with the assistance of an accretion disk that transports gas and dust from the envelope of the system to the star, and a jet that removes angular momentum and allows accretion to proceed. In the radio, these ionized jets can be studied very close to the star via the thermal (free-free) ...

High-luminosity active galactic nuclei (AGNs) powered by accretion onto a massive black hole (or other compact object) may have bolometric luminosities dominated by thermal emission from a geometrically thick accretion disk. Radiation from these disks is strongly anisotropic, which has ...

An increasing number of active galactic nuclei (AGNs) exhibit broad, double-peaked Balmer emission lines, which represent some of the best evidence for the existence of relatively large-scale accretion disks in AGNs. A set of 20 double-peaked emitters have been monitored for nearly a decade in order to observe long-term variations in ...

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 balanced conduction ...

We present the results of an imaging survey of protoplanetary disks around single T Tauri stars in Taurus. Thermal emission at 2 mm from dust in the disks has been imaged with a maximum spatial resolution of 1" by using the Nobeyama Millimeter Array. Disk images have been successfully obtained under almost uniform ...

Latest observational data provides evidence that the emissions from Sgr A* originate from an accretion disc within ten gravitational radii of the dynamical centre of Milky Way. We investigate the physical processes responsible for the variable observed emissions from the compact radio source Sgr A*. We study the evolution of 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. ...

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 imaging techniques, we ...

I investigate the evolution of 3 Myr-old MIPS-detected circumstellar disks in IC 348 that may be in an intermediate stage between primordial, optically-thick disks of gas/dust and debris disks characteristic of the final stages of planet formation. I demonstrate that these anemic disks are not a homogenous class ...

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 ...

A major issue for understanding the accretion process of AGN is determining the structure of the inner accretion disk. The only way to map the disk at distances < 1 pc from the central supermassive black hole is by using radio interferometric observations of nuclear water masers. In a new study of the nuclear ...

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. ...

Herbig Ae/Be stars are pre-main-sequence stars of intermediate mass, which are still accreting material from their environment, probably via a disk composed of gas and dust. Here we present a recent study of the geometry of the inner (AU-scale) circumstellar region around the Herbig Be star MWC 147 using long-baseline interferometry. By combining for the ...

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

A possible accretion model associated with the ionization instability of quasar disks is proposed to

Current astrophysical research suggests that the most persistently luminous objects in the Universe are powered by the flow of matter through accretion disks onto black holes. Accretion disk systems are observed to emit copious radiation across the electromagnetic spectrum, each energy band providing access to ...

The massive black hole at the Galactic Centre is known to be variable in radio, millimeter, near-IR and X-rays. We investigate the physical processes responsible for the variable observed emissions from the compact radio source, Sgr A*. We study the evolution of the variable emission region and present light curves and time-resolved spectra of ...

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 ...

We present the first detailed phase-resolved spectral analysis of a joint Chandra High-Energy Transmission Grating Spectrometer and Rossi X-ray Timing Explorer observation of the ? variability class in the microquasar GRS 1915+105. The ? cycle displays a high-amplitude, double-peaked flare that recurs roughly every 50 s and is sometimes referred to as the "heartbeat" oscillation. The spectral and ...

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 ...

Understanding black hole systems in their canonical hard state is a major goal of high energy astrophysics. This state features a hard X-ray spectrum, a high level of timing noise, and emission from a jet at radio, infrared, and perhaps higher frequencies. Observations can constrain the theoretical models by answering two questions: Does the inner edge of the ...

The energetics of a ..gamma..-ray burster can be explained by the rapid accretion of > or approx. =10/sup 19/ g of matter onto a neutron star surface. It is proposed that this sudden infall of matter may be the result of a radiation-driven instability which occurs at the boundary between an accretion disk and the surface of a slowly ...

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. ...

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 ...

Dec 19, 1999 ... Here gas from a blue giant star is shown being stripped away into an accretion disk around its compact binary companion. ...