We calculate the structure of an effectively optically thin and geometrically thin accretion disk in

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 ...

data yield the accretion disk thickness, diameter, electron density, and magnetic field. Introduction. The structure of AGN accretion disks on sub-parsec ...

Equations for the structure and appearance of supercritical accretion disks and the radiation-driven

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. ...

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 spatial and temporal development of protoplanetary accretion disks is investigated. Flat, homogeneous, mixed gas/dust disks with interstellar elementary frequencies, whose motion is estimated by the gravitation field of the central object, are conside...

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...

A simplified model of the vertical structure of accretion disks is derived. Analytical expressions for the temperature and density structure, which represent a generalization of the gray model long known in the theory of classical stellar atmospheres, are presented. The formalism naturally explains similarities and ...

Neutron Stars, Pulsars, Millisecond Pulsars, and Gravitational Radiation: GLOSSARY. Accretion disk: The flattened, pancake-like structure formed by matter ...

The solution for the radial drift velocity of thin disk accretion onto black holes must be transonic, and is analogous to the critical solution in spherical Bondi accretion, except for the presence of angular momentum. The transonic requirement yields a correct treatment of the inner region of the disk not found in ...

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

A powerful new method to determine the structure of effectively optically thin accretion disks is described. The method reduces the set of equations needed to be numerically solved to the microphysical equations only and reduces the dimension of the parameter space needed to be explored from three to two. It is shown why proton optical ...

A powerful new method to determine the structure of effectively optically thin accretion disks is described. The method reduces the set of equations needed to be numerically solved to the microphysical equations only and reduces the dimension of the parameter space needed to be explored from three to two. It is shown why proton optical ...

A method is proposed for restoring the structure of the accretion disk in a binary system from analysis of eclipse curves. Application of the method to the x-ray binary HZ Herculis yields the distribution of brightness and color temperatures over the optical accretion disk associated with the ...

The response of a circular accretion disk to rapid modulation of the mass-transfer rate into the disk is explored in order to model superhumps in SU UMa stars. It is proposed that periodically enhanced flow may disrupt or heat up the outer disk and produce the dips noted just before the superhump peaks. The ...

Results of two-dimensional gas dynamic computations of gas flow in symbiotic stars are presented, with radiation cooling of gas in the forming accretion disk taken into consideration. As computations show, radiation cooling does not change qualitatively the picture of the flow in the vicinity of the accreting star. The ...

Observations of T Tauri stars and young brown dwarfs suggest that the accretion rates of their disks

A model for disk accretion by a rotating magnetic neutron star is proposed which includes a detailed

We have constructed models for the vertical structure of disks around a black hole of 10/sup 6/ M/sub sun/ at distances from it smaller than the tidal breakup radius. These disks are massive enough that nuclear burning occurs in their central layers.

In thin accretion disks which are influenced by some nonaxisymmetric force (typically related to a precession effect), disk rings of different radii may lie in different planes. We derive the time-independent ''twist-equation,'' which governs the global structure of such a ...

The basic characteristics of line-driven winds from UV accretion disks were investigated analytically and numerically. Stellar winds have been compared with the outflow from a disk surrounding a supermassive black hole. It is found that in the approximation of vertically streaming radiation close to the disk ...

The authors have investigated both analytically and numerically the basic characteristics of line-driven winds from UV accretion disks. Stellar winds have been compared with the outflow from a disk surrounding a supermassive black hole. The authors find that in the approximation of vertically streaming radiation close to the ...

Convection driven by the turbulence of a thin accretion disk could play an important role in the disk structure and stability. A new high-surface-density state of the inner X-ray disk that is secularly stable is discovered when a certain parameter ..beta.. characterizing convective transport ...

The nonlinear evolution and spatial propagation of the thermal instability in accretion disks in galactic nuclei are investigated. Integrations of the vertical structure of the disks are described for different alpha prescriptions, and the thermal stability is examined. Global time-dependent calculations of the ...

Active galactic nuclei (AGN) are powered by accretion and recent observations indicate the existence of accretion disks around a central black hole of 108 to 1010Msun. A derivation and discussion of the basic equations for the structure of a thin accretion disk around a ...

Most Galaxy-sized systems (M host sime 1012 M sun) in the ?CDM cosmology are expected to have interacted with at least one satellite with a total mass M sat sime 1011 M sun sime 3M disk in the past 8 Gyr. Analytic and numerical investigations suggest that this is the most precarious type of accretion for the survival of thin galactic ...

Analysis of thick, radiation pressure dominated (super-Eddington) accretion disks has proven to be difficult. Purely analytical methods have not yet been adequate to determine the structure of the disk and associated jet. The work presented here circumvents the analytical problems by using a numerical method; the ...

The thermal equilibrum structure and dynamical behavior of externally irradiated accretion disks are investigated. For radiative disks only the surface layer is heated, while for convective disks the heat penetrates deeply into the disk. For sufficiently strong radiation ...

To study the outflows from accretion disks, we solve the set of hydrodynamic equations for accretion disks in spherical coordinates (r?phi) to obtain the explicit structure along the ?-direction. Using self-similar assumptions in the radial direction, we change the equations to a set of ...

Theoretical calculations of linear polarization of thermal radiation from accretion disks in nova-like variables and dwarf novae in eruption are presented. The primary source of polarization is due to electron scattering in the disk's photosphere. It is shown that the degree of polarization can be used as a powerful probe of ...

We study the accretion process in the region of the Preston-Poisson space-time describing a Schwarzschild black hole perturbed by an asymptotically uniform magnetic field and axisymmetric tidal structures. We find that the accretion disk shrinks and the marginally stable orbit shifts toward the black hole with the ...

Young stellar systems orbiting in the potential of their birth cluster can accrete from the dense molecular interstellar medium during the period between the star's birth and the dispersal of the cluster's gas. Over this time, which may span several Myr, the amount of material accreted can rival the amount in the initial protoplanetary ...

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 ...

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 ...

We derive the evolution equations describing a thin axisymmetric disk of gas and stars with an arbitrary rotation curve that is kept in a state of marginal gravitational instability and energy equilibrium due to the balance between energy released by accretion and energy lost due to decay of turbulence. Rather than adopting a parameterized ? prescription, ...

The understanding of accretion processes and in particular of massive accretion disks is one of the most important topics in high-mass star formation. Based on our successful ATCA disk studies of high mass star formation, we now propose to investigate higher J inversion transitions of NH3 at high angular resolution ...

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 line profiles and ...

A study of both the physical and the thermodynamical characteristics of a satellitary accretion disk around Saturn has been performed in order to investigate the primordial stages of the formation of the Saturn satellites. In particular, the evolution of a satellitary disk during the infall of material from the surrounding cloud is ...

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 ...

Mar 1, 2011... common to both state extremes: a low temperature accretion disk, .... The Development of Magnesium-Lithium Alloys for Structural ...

Mass accretion onto (proto-)stars at high accretion rates \\dot{M}_* > 10^{-4} M_{&sun;} yr^{-1} is expected in massive star formation. We study the evolution of massive protostars at such high rates by numerically solving the stellar structure equations. In this paper, we examine the evolution via disk ...

The IUE was used to study processes connected with accretion disk structure and stability, wind accretion and wind-wind collisions, contact systems, and stellar activity in close binary stars. Time dependent phenomena already known from optical studies ap...

We have investigated the influence of X-ray irradiation on the vertical structure of the outer accretion disk in low-mass X-ray binaries by performing a self-consistent calculation of the vertical structure and X-ray radiation transfer in the disk. Penetrating deep into the ...

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 methanol, a molecule that is ...

Measurements of the polarization of X-rays from Cyg X-1 can yield significant information about the structure of the accretion disk which produces the observed spectrum. In particular, both the physical geometry (sensitive to large changes in the viscosity) and also the soft X-ray cutoff of the inner region of 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 ...

Several types of cataclysmic events involving stellar-mass compact objects could result in the extreme, transient accretion onto a black hole widely believed to power gamma-ray bursts. We calculate the vertical structure of such thick accretion disks with a semi-analytical model which includes the effects of ...

The linear equations that describe the thermal stability of the convective and radiative vertical structure of an alpha model accretion disk are derived. For a specific model chosen to be representative of a dwarf nova disk, it is found that the eigenfunction for the temperature shows large excursions in the zone ...

We discuss the dynamics of the accretion flow onto a black hole driven by Poynting flux in a simplified model of a two-dimensional accretion disk. In this simplified model, the condition of the stationary accretion flow is found to impose a nontrivial constraint on the magnetic field configuration. The effect of ...

The dynamics and structure of accretion disks, which accumulate a vertical magnetic field in their centers, are investigated using two- and three-dimensional MHD simulations. The central field can be built up to the equipartition level, where it disrupts a nearly axisymmetric outer accretion ...

This is the first of two papers that investigate models of radiation-driven winds from super-critical accretion disks. The main assumptions in the models are that the mass and luminosity in the wind emanate from the radius in the disk where accretion becomes supercritical (the critical radius) and that the wind is ...

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, ...

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 ...

We consider the effects of ``photon bubble'' shock trains on the vertical structure of radiation pressure-dominated accretion disks. These density inhomogeneities are expected to develop spontaneously in radiation-dominated accretion disks where magnetic pressure exceeds gas pressure, even in ...

Using data from the Rossi X-Ray Timing Explorer, we investigate the spectral evolution along a "Z" track and a "?" track on the hardness-intensity diagrams of the first transient Z source XTE J1701�462. The spectral analyses suggest that the inner disk radius depends on the mass accretion rate, in agreement with the model prediction, R_in \\propto ...

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 vertical temperature ...

The purpose of the two-day Workshop on Physics of Accretion Disks Around Compact and Young Stars was

An effort is made to observationally constrain accretion disks on the basis of light curves from the

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 that the absorption ...

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 ...

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

We investigate the structure of accretion disks around massive protostar applying steady state models of thin disks. The thin disk equations are solved with proper opacities for dust and gas taking into account the huge temperature variation along the disk. We explore a ...

Aims: Cold steady-state disk wind theory from near Keplerian accretion disks requires a large scale magnetic field at near equipartition strength. However the minimum magnetization has never been tested with time dependent simulations. We investigate the time evolution of a Shakura-Sunyaev accretion ...

``Corrugated'' plasma disks can form in the dominant gravity of a central object when the peak plasma pressure in the disk is of the same order as that of the pressure of the ``external'' magnetic field, while the magnetic field resulting from internal plasma currents is of the same order as the external field. The corrugation refers to a periodic ...

The hot thermal accretion disks of the 1970s are studied and consideration is given to the effects of electron-positron pairs, which were originally neglected. It is found that disks cooled by internally produced photons have a critical accretion rate above which equilibrium is not possible in a radial annulus ...

Using Spitzer Space Telescope photometric observations of the eclipsing, interacting binary WZ Sge, we have discovered that the accretion disk is far more complex than previously believed. Our 4.5 and 8 ?m time series observations reveal that the well-known gaseous accretion disk is surrounded by an asymmetric ...

(Abridged) We perform dissipationless N-body simulations to elucidate the dynamical response of thin disks to bombardment by cold dark matter (CDM) substructure. Our method combines (1) cosmological simulations of the formation of Milky Way (MW)-sized CDM halos to derive the properties of substructure and (2) controlled numerical experiments of consecutive subhalo impacts onto ...

Photoelectric U, B, V photometry of eclipses in the close binary system IP Peg, obtained mainly with the 6-m telescope, yields brightness profiles along the edgewise accretion disk. The radiation is dominated by a hot spot whose brightness and location in the disk depend on the state of activity in the binary. In the quiescent phase ...

The formation of thick stellar disks in spiral galaxies is studied. Simulations of gas-rich young galaxies show formation of internal clumps by gravitational instabilities, clump coalescence into a bulge, and disk thickening by strong stellar scattering. The bulge and thick disks of modern galaxies may form this way. Simulations of ...

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, ...

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 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 ...

Following a suggestion by Paczynski we have constructed models for the vertical structure of disks around stars in their late stages of evolution in which the viscosity that allows the angular momentum of the disk to be transported outward is due solely to turbulence produced by convection in the outer layers of the ...

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 ...

Cold steady-state disk wind theory from near Keplerian accretion disks requires a large scale magnetic field at near equipartition strength. However the minimum magnetization has never been tested. We investigate the time evolution of an accretion disk threaded by a weak vertical magnetic ...

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

Spectroscopic, time-resolved observations of the accretion disk in the long-period Algol system RY Gem during eclipse are presented. It is shown that the disk is non-Keplerian and has asymmetries between the leading and trailing sides of the accretion disk similar to those seen in the transient ...

We compute the properties of a geometrically thin, steady accretion disk surrounding a central rotating, magnetized star. The magnetosphere is assumed to entrain the disk over a wide range of radii. The model is simplified in that we adopt two (alternate) ad hoc, but plausible, expressions for the azimuthal component of the magnetic ...

Hydromagnetic disk winds have great potential as a general theory for the production and collimation of astrophysical jets in both protostellar and black hole environments. We first review the analytic stationary theory of these outflows as well as recent numerical simulations of MHD disk winds. We then focus on simulations that we have done on winds from ...

Accretion disks are associated with such diverse objects as planetary systems, Be stars, and spiral galaxies. However, their structure is poorly defined by existng observational data. This study was an attempt to gather specific structural information about the disks in Algol-type binary ...

X-rays from young stellar objects can influence the physical properties of their surroundings. A particularly interesting example is the ionization of the accretion disk by hard X-rays at distances of the order of 1 AU or more. The authors show that X-rays induce a layered ionization structure in which the outer layer is sufficiently ...

.1 Planetological History of the Early Earth Chapter 2 described how the collapse of the core of an interstellar3 The Earth The previous chapter brie y outlined how from an accretion disk ? the end product to look more closely at the basic structure and composition of the singular planet Earth where life

A cascade model for driven quasi-steady fluid turbulence is applied to calculation of the dissipation parameter, alpha, for a convection-accretion disk. The mode analysis is nonlocal in the vertical direction and allows arbitrary rotation curves. Nonaxisymmetric modes, nonlinear mode structure, and turbulent cascade dynamics are all ...

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...

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 ...

The understanding of accretion processes and specifically of massive accretion disks is considered the holy grail in high-mass star formation. We propose to study the recently identified massive accretion disk candidate IRAS18089-1732 at high angular resolution (<0.7'') in the highly excited ...

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 ...

Herbig Ae/Be stars(HAeBes) are young stellar objects of spectral class F2 through B0, with the central star often surrounded by a circumstellar disk of gas and dust. They are the higher mass analogs to T Tauri stars. The interaction between the star and the disk is not well understood, nor is the disk structure. ...

Jets and outflows are observed around a wide variety of accreting objects and seem to be a near-ubiquitous feature of accretion disks. Large-scale magnetic fields are often thought necessary for jet formation, but a longstanding puzzle is that the turbulence which is responsible for inward disk ...

Accretion disk-driven magneto-centrigugal winds are one of the leading mechanism for producing bipolar outflows in many astrophysical systems. Previous studies of this mechanism have concentrated either on the disk or on the wind. We show that the structures of the disk and the wind are ...

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? ...

Context. Even though turbulent motions are found everywhere in astrophysical systems, the origin of this turbulence is poorly understood. When cosmic structures form, they grow in mass via accretion from their surrounding environment. Aims: We propose that accretion is able to drive internal turbulent motions in a wide range of ...

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 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 in an ...

Observations of X-ray binaries indicate substantial half-thicknesses for the accretion disks in these systems (up to h/R ? 0.25, where h is the disk half-thickness and R its radius), while standard ? accretion disks predict appreciably smaller half-thicknesses. We study the theoretical vertical ...

We have constructed vertically integrated, steady state convective models of accretion disks to explore the mechanism of instability in dwarf novae. The models and observations of dwarf novae suggest a picture in which transferred matter piles up in an optically thin torus. The torus eventually becomes optically thick and the resulting convective ...

Vertically integrated, steady state convective models of accretion disks have been constructed to explore the mechanism of instability in dwarf novae. The models and observations of dwarf novae suggest a picture in which transferred matter piles up in an optically thin torus. The torus eventually becomes optically thick, and the resulting convective ...

The magnetorotational instability (MRI) is the most likely candidate for angular momentum transport and radial flow of mass in protoplanetary disks (PPDs), but demands a minimum ionization fraction for the gas to couple to the magnetic field. It is known that large regions of PPDs are insufficiently ionized for the MRI to act, and are �dead zones.� Only at the ...

The conference Galaxy Disks and Disk Galaxies, sponsored by the Vatican Observatory, was held in June 12-16, 2000 at the Pontifical Gregorian University, in Rome (Italy). The meeting hosted about 230 participants coming from 30 countries. The very full program consisted of 29 review papers, 34 invited talks, and more than 180 posters. The meeting covered ...

About half of the binary systems are close enough to each other for mass to be exchanged between them at some point in their evolution, yet the accretion mechanism in wind accreting binaries is not well understood. We study the dynamical effects of gravitational focusing by a binary companion on winds from late-type stars. In particular, we investigate the ...

Mass accretion onto (proto-)stars at high accretion rates M-dot{sub *}> 10{sup -4} M{sub sun} yr{sup -1} is expected in massive star formation. We study the evolution of massive protostars at such high rates by numerically solving the stellar structure equations. In this paper, we examine the evolution via ...

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 disk ...

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 vertical temperature ...

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 ...

In massive star formation (gsim 40 M sun) by core accretion, the direct stellar radiation pressure acting on the dust particles exceeds the gravitational force and interferes with mass accretion at the dust sublimation front, the first absorption site. Ram pressure generated by high accretion rates of 10-3 M sun yr-1 is thought to be ...

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 accretion ...

As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. ...

As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. ...

We investigate stationary slim accretion disks around Kerr black holes. We construct a new numerical method based on the relaxation technique. We systematically cover the whole parameter space relevant to stellar mass X-ray binaries. We also notice some non-monotonic features in the disk structure, overlooked in ...

a simple, height�averaged, self�similar model of ad� vective accretion disk threaded by a large�scale magnetic field (with open field lines), and have shown that the disk structure and the magnetic field lines (dragging effect), and the intensity of the magnetic field deter� mines the ...

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 ...

The formation and evolution of the circumstellar disk in unmagnetized molecular clouds is investigated using three-dimensional hydrodynamic simulations from the prestellar core until the end of the main accretion phase. In collapsing cloud cores, the first (adiabatic) core with a size of gsim3 AU forms prior to the formation of the protostar. At its ...

The formation and evolution of the circumstellar disk in unmagnetized molecular clouds is investigated using three-dimensional hydrodynamic simulations from the prestellar core until the end of the main accretion phase. In collapsing cloud cores, the first (adiabatic) core with a size of {approx}>3 AU forms prior to the formation of the protostar. ...

The structure of protoplanetary disks within 1 AU of their central stars has important implications for terrestrial planet formation, giant planet migration, and disk accretion. Near-IR interferometry presents the unique opportunity to spatially resolve inner disk regions, and recent ...

In theory of accretion disks, angular momentum and mass transfer are associated with the generation of energy through viscous dissipation. In the construction of SED models of protostellar disks, the stellar irradiation is usually assumed to be the dominant heating source. Here we construct a new set of self-consistent analytical ...

Cataclysmic variables (CVs) are a nearby, non-obscured population of systems in which the physics of accretion, particularly disk accretion, can be studied. FUV observations of CVs target the disk, disk winds and the white dwarf (WD); with FUSE, we can address questions concerning the ...

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 ...

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 ...

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 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. ...

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 an X-ray study of the low-luminosity active galactic nucleus (AGN) in NGC 4258 using data

A model for the fluctuating hard component of intense cosmic X-ray sources (such as Cyg X-1) is developed, based upon the amplification of magnetic fields by convective motions and differential rotation within a hot (T> or approx. =10/sup 6/K) accretion disk. Field reconnection within the inner portion of the disk is shown to be ...

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 from 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

Returning radiation is radiation emitted by an accretion disk which returns to its surface due to gravitational focusing or the shape of the disk. While it is unimportant for thin disks around nonrotating black holes, returning radiation will have significant effects on the structure and ...

Recently, Ida et al. made an N-body simulation of lunar accretion from a protolunar disk formed by a giant impact. One of their important conclusions is that the accretion time of the Moon is as short as one month. Such rapid accretion is a necessary consequence of the high surface density of a lunar mass ...

Recent infrared observations of molecular lines by the Spitzer Space Telescope have revealed the chemical properties in the surface layers of planet-forming regions in protoplanetary disks. These observations, together with (sub)millimetre molecular line observations, are useful tools for diagnosing the physical and chemical properties of disks, key to our ...

A general class of stationary magnetic configurations which can exist in (thin) plasma accretion disks is identified by solving analytically the coupled nonlinear equations that describe the radial and the vertical equilibrium conditions of the disk. These configurations are characterized by a ...

The accretion disks around pre-main-sequence stars provide the raw material and initial conditions for the formation of planetary systems. Disk chemistry is thus essential to predict the composition of planetesimals and eventually planets - comet compositions in our own solar system reveal that efficient astrophysical pathways to ...

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 reexamine the dynamic response of a thin, accretion disk to twisting torques, guided by the earlier analyses by Bardeen and Petterson. We make several corrections to this earlier work, and present a new version of the twist equations consistent with their physical assumptions. By describing the distortion of the disk in terms ...

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 ...

Jan 31, 2005 ... KERRBB is a multi-temperature blackbody model for a thin, steady state, general relativistic accretion disk around a Kerr black hole. ...

The thesis consists of an introduction and summary, and five research papers. The introduction and summary provides the background in accretion disk physics and magnetohydrodynamics. The research papers describe numerical studies of magnetohydrodynamical ...

First � Previous � Next � Last � Index � Home � Text. Long-term Periodicities and Accretion Disks. Slide 4 of 22.

Jan 22, 2010 ... Many astrophysical objects, including neutron stars and accretion disks, are powered by a combination of very strong magnetic fields and ...

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

Jun 11, 2010 ... Relativistic Illumination Law from Accretion Disks ... Relativistic Iron Fluorescent Line from Accretion Disks ...

Quasar Jets and Accretion Disks. Questions: " Does the most compact optical emission from an AGN come from an accretion disk or from a relativistic jet? ...

Binary Black Holes, Accretion Disks and Relativistic. Jets: Photocenters of Nearby AGN and Quasars. Principal Investigator: Ann E. Wehrle (Interferometry ...

Accretion Disk Coronae were first suggested to explain the incomplete eclipses and shallow profiles observed from some Low Mass X-ray Binaries (White and ...

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 ...