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

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, ...

... Understanding of accretion disks, accretion flows, X-ray induced winds, compact obect evolution are all in a primitive state. ...

The polytropic relation between pressure and density of wind gases is used to obtain solutions for optically thin hot accretion disks with winds. It is assumed that the cooling mechanisms in the disks are bremsstrahlung and Compton scattering. This extends the previous work of Takahara et al. ...

How do accretion disks launch winds and jets? From the Fundamental Accretion and Ejection Astrophysics Astro2010. White Paper, Miller et al. ...

We herein present an observational and theoretical review of the winds of compact binaries. After a brief consideration of the accretion disk coronae and winds of X-ray binaries, the review concentrates on the winds of cataclysmic variables (CVs). Specifically, we consider the related problems ...

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 ...

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 ...

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 they ...

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...

(� \\Gamma5 km s \\Gamma1 ), possibly associated with a disk wind or magnetic accretion columns. The velocity (Beckwith and Sargent, 1993; Strom et al. 1993). Evidence that these disks accrete onto the stellar surface protostellar disks form and evolve (Strom, Edwards and ...

Jun 28, 2007 ... Hydrodynamic Models of Line-driven Accretion Disk Winds. III. ... Hydrodynamic Modeling of Cataclysmic Variable Winds ...

A theory for the formation and propagation of nonrelativistic jets and winds from magnetized accretion disks is derived from the equation of ideal magnetohydrodynamics. The theory allows the self consistent determination of the jet's axial velocity, radiu...

We present new results from the Chandra HETGS on the accretion disk wind in the bizarre ? state of GRS 1915+105. Renowned for its discrete jet ejections and its implications for the disk-jet connection around accreting black holes, the ? state is a 30-minute limit cycle featuring strong and ...

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 ...

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

It is suggested that the pre-main-sequence object Z CMa is a luminous accretion disk, similar in many respects to the FU Orionis variables. Z CMa shows the broad, doubled optical absorption lines expected from a rapidly rotating accretion disk. The first overtone CO absorption detected in Z CMa is blue-shifted, ...

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 third yearbook of the Astronomische Gesellschaft (AG) contains 19 contributions dedicated to the topic "Accretion and Winds". Modern developments in accretion-disk theory are presented; accretion disks are considered in close binaries, cataclysmic variables, neutron stars, and galaxies. ...

A general mechanism is presented for generating pressure-driven winds that are intrinsically bipolar from objects undergoing disk accretion. The energy librated in a boundary layer shock as the disk matter impacts the central object is shown to be sufficient to eject a fraction ..beta..approx.10/sup -2/ to 10/sup ...

Hydrodynamical winds from hot accretion disks around compact objects are investigated using a simplified model. The flow pattern above the disk is solved assuming that specific angular momentum is conserved along a stream line and that the radial component of the gravitational force balances the centrifugal force ...

The collapse of massive molecular clumps can produce high mass stars, but the evolution is not simply a scaled-up version of low mass star formation. Outflows and radiative effects strongly hinder the formation of massive stars via accretion. A necessary condition for accretion growth of a hydrostatic object up to high masses M > 20 MSun (rather than ...

The wind accretor LMC X-1, along with LMC X-3 and Cygnus X-1, is one of only three known persistently bright black hole binary systems. Our long-term RXTE monitoring campaign of LMC X-1 has revealed a surprising departure from the typical accretion disk temperature-luminosity relation. This behavior is consistent with the presence of a ...

The IUE data base is used to analyze the UV line shapes of cataclysmic variables RW Sex, RW Tri, and

The IUE data base is used to analyze the UV line shapes of cataclysmic variables RW Sex, RW Tri, and V Sge. Observed lines are compared to synthetic line profiles computed using a model of rotating bi-conical winds from accretion disks. The wind model cal...

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 involvement of accretion disks around supermassive black holes in the theory of active galactic nuclei (AGN) is discussed. The physics of thin and thick accretion disks is discussed and the partition between thermal and nonthermal energy production in supermassive disks is seen as ...

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 ...

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 ...

The US/Russia collaboration in plasma astrophysics combines the efforts of scientists from two groups -- the Russian Academy of Science Institutes and Cornell University -- to solve many of the complicated problems associated with the magnetohydrodynamical (MHD). Students and educators can find thorough descriptions about the collaboration's studies in wind ...

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

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 disk. That is, the gas was assumed to be highly supersonic. Figure 7 shows the averaged Mach number for the infalling wind as it impacts the disk. On average, the gas is indeed supersonic, but, particularly.--- Plot of the Mach number, averaged over OE and the two sides of the disk, of the gas impacting

. Figure 7 shows the averaged Mach number for the infalling wind as it impacts the disk. On average . #12; { 11 { Fig. 7.| Plot of the Mach number, averaged over #30; and the two sides of the disk, of the gas for the two runs are strongly correlated. Thus, the average rate of mass falling onto the disk is ...

We investigate nucleosynthesis inside both a gamma-ray burst accretion disk and a wind launched from an inner region of the disk using one-dimensional models of the disk and wind and a nuclear reaction network. Far from a central black hole, the composition of ...

The stability and evolution of windy accretion disks is investigated in detail. The basic disk evolution equations are briefly recapitulated, and an idealized analytic treatment of the wind and viscosity is used to show that steady disk flow is indeed unstable for sufficiently large ratio of ...

Although disk accretion onto compact objects-white dwarfs, neutron stars and black holes-is central to much of high-energy astrophysics, the mechanisms that enable this process have remained observationally difficult to determine. Accretion disks must transfer angular momentum in order for matter to travel radially ...

Steady state models of magnetized accretion disks that power centrifugally driven outflows are presented. Self-similar solutions for Keplerian disks that are dominated by ambipolar diffusion are constructed and the analogous solutions for resistive disks are presented. In each case, it is shown that one can obtain ...

Ultraviolet resonance lines appear to be powerful tools for diagnostics and study of the outflows from cataclysmic variable stars. The origin of these winds and their geometry are not known at present. In order to compare observed lines from the IUE database with synthetic line profiles from accretion disk winds, ...

Aims. We investigate the accretion process from an accretion disk onto a magnetized rotating star with a purely dipolar magnetic field. Our main aim is to study the mechanisms that regulate the stellar angular momentum. In this work, we consider two effects that can contrast with the spin-up torque normally associated with ...

The authors present an observational and theoretical review of the winds of cataclysmic variables (CVs). Specifically, they consider the related problems of the geometry and mass-loss rate of the winds of CVs, their ionization state and variability, and the results from studies of eclipsing CVs. Finally, they consider the properties of ...

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 disk ...

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 ...

Models predict that magnetic fields play a crucial role in the physics of astrophysical accretion disks and their associated winds and jets. For example, the rotation of the disk twists around the rotation axis the initially vertical magnetic field, which responds by slowing down the plasma in the ...

Recent observations of stellar-mass black holes have revealed evidence of black hole spin, disk winds, and aspects of how accretion flows vary with the mass accretion rate. We propose to build on these successes with a single 40 ksec (total) observation of a black hole transient in outburst. Though modest, this ...

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 ...

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 ...

Radiative winds and jets from luminous accretion disks/tori are reviewed. Among various models of astrophysical jets, plasma outflows emanating from accretion disks/tori and accelerated by the radiation pressure is the most promising one. Here explained are the roles of radiation pressure force ...

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 ...

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 ...

High Energy Astrophysics: Accretion Disks I 1/60 Accretion Disks I References: Accretion Power in Astrophysics, J. Frank, A. King and D. Raine. High Energy Astrophysics, Vol. 2, M.S. Longair, Cambridge Astrophysics: Accretion Disks I 2/60 1 Overview ...

We present a new 2D ray-tracing technique for computing the emergent spectra of winds originating from the surfaces of primary star and accretion disk in cataclysmic binaries. By using a highly modular approach, allowing easy modification and extension of the code, we self-consistently solve the pan-chromatic radiative transfer problem ...

We present new insights about accretion and ejection physics based on joint RXTE/Chandra HETGS studies of rapid X-ray variability in GRS 1915+105. For the first time, with fast phase-resolved spectroscopy of the ? state, we are able to show that changes in the broadband X-ray spectrum (RXTE) on timescales of seconds are associated with measurable changes in absorption lines ...

We investigate nucleosynthesis inside both a gamma-ray burst accretion disk and a wind launched from an inner region of the disk using one-dimensional models of the disk and wind. Far from a central black hole, the composition of accreting gas is taken ...

The supercritical wind theory of Papers II and III is applied to winds driven by accretion phenomena. An expression for the total luminosity LT is derived in terms of the accretion rate dotMT and injection radius r?. When applied specifically to accretion disks, the theory ...

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 the presence of ...

We present the results of hydrodynamical simulations of the disk photosphere irradiated by strong X-rays produced in the innermost part of the disk of an accreting black hole. As expected, the irradiation heats the photosphere and drives a thermal wind. To apply our results to the well-studied X-ray transient ...

The magnetocentrifugal disk wind mechanism is the leading candidate for producing the large-scale, bipolar jets commonly seen in protostellar systems. I present a detailed formulation of a global, radially self-similar model for a non-ideal disk that launches a magnetocentrifugal wind. This formulation generalizes ...

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 ...

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, ...

An analytic model is proposed for nonradiating accretion flows accompanied by up or down winds in a global magnetic field. Physical quantities in this model solution are written in variable-separated forms, and their radial parts are simple power-law functions that include one parameter for wind strength. Several mathematically ...

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 emission lasting over a few ...

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 ...

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

We analyze the dynamics of two-dimensional stationary, line-driven winds from accretion disks in cataclysmic variable stars. The driving force is that of line radiation pressure, in the formalism developed by Castor, Abbott, & Klein for O stars. Our main assumption is that wind helical streamlines lie on ...

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 ...

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

I present new insights about accretion and ejection physics in low-mass X-ray binaries based on high-resolution Chandra HETGS studies of accretion disk winds in the microquasar GRS 1915+105. First, using 10 years of Chandra observations to probe the long-term connection between accretion ...

Young stars can produce X-rays by different mechanisms: Coronal activity, accretion shocks and shocks in outflows. We propose to observe two targets within one field-of-view (FOV): SU Aur is accreting mass from a disk and shows violent coronal activity. We will study the time evolution of stellar flares on time scales from seconds to ...

A model involving binary mass transfer and accretion onto main sequence stars is developed to explain the brightest known stars in external galaxies, the Hubble-Sandage variables. The similarity in spectral properties between the Hubble-Sandage variables and cataclysmic variables and the extreme disparity in their luminosities are presented as evidence for the essential ...

A simple model of the boundary layer and accretion disk wind of dwarf novae in outburst is briefly described and applied to the Chandra Low Energy Transmission Grating spectra of WZ Sge and SS Cyg in outburst.

A simple model of the boundary layer and accretion disk wind of dwarf novae in outburst is briefly described and applied to the Chandra Low Energy Transmission Grating spectra of WZ Sge and SS Cyg in outburst.

We analyze the dynamics of two-dimensional stationary, line-driven winds from accretion disks in cataclysmic variable (CV) stars by generalizing the formalism of Castor, Abbott, and Klein (CAK) for O stars. In Paper I, we solved the wind Euler equation, derived its two eigenvalues, and addressed the solution ...

I calculate the specific angular momentum of mass accreted by a binary system embedded in the dense wind of a mass losing asymptotic giant branch star. The accretion flow is of the Bondi-Hoyle-Lyttleton type. For most of the relevant parameters space the flow is basically an isothermal high Mach number accretion ...

The magnetocentrifugal disk wind mechanism is the leading candidate for producing the large-scale, bipolar jets commonly seen in protostellar systems. I present a detailed formulation of a global, radially self-similar model for a fully general, non-ideal disk that launches a magnetocentrifugal disk ...

It is plausible that an accretion disk pumps energy into an outer tenuous layer of its atmosphere to form a high-tmeperature corona analogous to the solar corona. General features of such a corona, not specific to any model, are discussed, and order-of-magnitude estimates are made for the physical parameters of a corona on the Cygnus X-1 ...

We propose to continue our ongoing study of Galactic black hole transients in outburst in a streamlined form, via two (2) 30 ksec HETGS observations. This program has revealed relativistic Fe K disk lines, warm-absorber-like disk winds, and now a possible anti-correlation between winds and jets. Observations of a ...

We propose to continue our ongoing study of Galactic black hole transients in outburst in a streamlined form, via two (2) 30 ksec HETGS observations. This program has revealed relativistic Fe K disk lines, warm-absorber-like disk winds, and now a possible anti-correlation between winds and jets. Observations of a ...

We propose to continue our ongoing study of Galactic black hole transients in outburst in a streamlined form, via two (2) 30 ksec HETGS observations. This program has revealed relativistic Fe K disk lines, warm-absorber-like disk winds, and now a possible anti-correlation between winds and jets. Observations of a ...

Recent theoretical advances in our understanding of the dynamics of circumstellar accretion disks are reviewed. Of particular importance are developments regarding angular momentum transport processes in disks. It has recently been shown through direct numerical simulation that vertical convection results in inward transport, and thus ...

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 ...

We construct a model for supercritical accretion disks with winds, where the mass-accretion rate highly exceeds the Eddington rate and a significant fraction of the accreting gas is expelled as a superwind, under a self-similar treatment. The mass-accretion rate dot{M} ...

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 ...

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. The central star will ...

Nov 6, 2000 ... "accretion" means collecting of additional material. Two major places where astronomers see accretion disks are in binary star systems (two ...

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 ...

The third yearbook of the Astronomische Gesellschaft (AG) contains 19 contributions, presented during the spring meeting of the AG, Berlin (Germany), Mar 1990, dedicated to the topic "accretion and winds". Modern developments in accreption-disk theory are presented; accretion disks are ...

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

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 investigate the effects of ...

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 this paper, we ...

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 ...

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...

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 ...

It is suggested that disk accretion provides the requisite external source to power the winds of T Tauri stars. As a test of this hypothesis, a potential accretion diagnostic for a representative sample of stars is compared to diagnostics of the wind strength. The luminosity of H-alpha, formed ...

We outline recent progress in understanding the accretion of plasma to rotating magnetized stars obtained from global axisymmetric (2D) and 3D magnetohydrodynamic (MHD) simulations in three main areas: (1.) Formation of jets from disk accretion onto rotating magnetized stars: From simulations where the viscosity and magnetic ...

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 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 ...

A large body of recent work points towards feedback processes related to the active accretion of matter onto supermassive black holes in the centers of most massive galaxies as being one of the primary regulatory processes for pc to Mpc scales in the Universe. We seek to close the gap in our knowledge of the physics behind active galactic nuclei (AGN) feedback processes by ...

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 high-mass eclipsing X-ray binary system SMC X-1/Sk 160 will be observed for one complete binary orbit (3.892 days) to provide a detailed far ultraviolet spectroscopic record of this important system. The spectra will be used to 1) characterize the phase-dependent X-ray ionization of the stellar wind and its density distribution, 2)study enhanced metal abundances in the ...

Near-infrared images (1-2.2 microns) of young stellar objects, where the light distribution results from diffusion and absorption of radiation of the central stellar object by circumstellar dust, are presented. The distribution of matter is modeled as a combination of a disk, a clump, and a wind-blown cavity. Various density laws for the ...

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 ...

Protostellar jets are most probably disk winds or stellar winds collimated by rotating magnetospheres. The structure of these magnetospheres follows from solutions of the Grad-Schlueter-Shafranov (GSS) equation for the force-balance between axisymmetric magnetic surfaces. In this paper, two-dimensional force-free solutions of the ...

I present new insights about accretion and ejection physics based on two high-resolution X-ray studies of strong variability in the microquasar GRS 1915+105. First, we use 10 years of Chandra HETGS observations to probe the long-term connection between the accretion disk wind and the radio jet. We find that the ...

Symbiotic stars appear almost certainly to be interacting binaries with a cool giant losing mass from its wind or by Roche lobe overflow to a much more compact companion. The latter is thought to be usually a white dwarf, but may sometimes be a main sequence star and perhaps even a neutron star. Symbiotic stars go through activity phases, which are thought to be sometimes due ...

Large-scale homogeneous surveys of Galactic stars may indicate that the elemental abundance gradient evolves with cosmic time, which is a phenomenon that was not foreseen in existing models of Galactic chemical evolution (GCE). If this phenomenon is confirmed in future studies, we can show that this effect, at least in part, is due to large-scale winds that once enriched the ...

The UV spectra of nova-like variables are dominated by emission from the accretion disk, modified by scattering in a wind emanating from the disk. Here, we model the spectra of RW Tri and UX UMa, the only two eclipsing nova-like variables which have been observed with the Hubble Space Telescope in the ...

It is well known that there is mass outflow in cataclysmic variables, since IUE observations show P Cyg profiles of various high-excitation lines of C IV and S IV. It is proposed here that these outflows are hydromagnetic winds from accretion disks. The winds extract angular momentum from these systems and ...

The IUE data base is used to analyze the UV line shapes of cataclysmic variables RW Sex, RW Tri, and V Sge. Observed lines are compared to synthetic line profiles computed using a model of rotating bi-conical winds from accretion disks. The wind model calculates the wind ionization structure ...

I will discuss results of 2D and 3D MHD simulations of disk accretion onto young rotating magnetized stars. The disk magnetosphere interaction leads to formation of funnel streams and hot spots on the stellar surface. The energy distribution in the spots is such that the highest energy photons are expected to radiate from the central ...

The aim of our research is to address why millisecond pulsars have relatively weak surface magnetic fields, of about 10^8 G, with a narrow spread. We propose that the accretion of plasma from the companion star fully screens the original neutron star field, but the accretion disk carries additional magnetic flux from the companion ...

.--- A schematic cross section through the star (in the center of the figuer) and disk (shown hatched) in a nova stars N. Murray and J. Chiang Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ONT M5S 3H8, Canada Cataclysmic variable stars are thought to consist of a low mass star orbiting

Galactic accreting compact objects, such as stellar-mass black holes and neutron stars, can give us a unique perspective into the behavior of matter in extreme conditions. However, the exact nature of accretion onto these objects is not yet well understood. X-ray studies provide us with a means to observe the innermost regions around these objects and to ...

Galactic accreting compact objects, such as stellar-mass black holes and neutron stars can give us a unique perspective into the behavior of matter in extreme conditions. However, the exact nature of accretion onto these objects is not yet well understood. X-ray studies provide us with a means to observe the innermost regions around these objects and to ...

Steady disk winds, or jets, from inner region of a geometrically thin accretion disk were studied under the assumption that the wind flow is confined within a hollow cylindrical-shell region. By using the cold-wind approximation, in which the variation of the flow ...

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 ...

In paper 1 (Chakrabarti & D'Silva 1994), we have studied the conditions under which flux tubes are expelled from adiabatic thick accretion disks. In the present paper, we explore a few other models of thick disks, where flux tubes could be stored. We show that flux tubes with sufficiently weak fields are not expelled out if they ...

We present direct evidence, from adaptive-optics near-infrared imaging, of the jets in the Galactic microquasar SS433 interacting with enhanced wind-outflow off the accretion disk that surrounds the black hole in this system. Radiant quantities of gas are transported significant distances away from the black hole approximately ...

We calculate the chemical evolution of protoplanetary disks considering radial viscous accretion, vertical turbulent mixing, and vertical disk winds. We study the effects on the disk chemical structure when different models for the formation of molecular hydrogen on dust grains are adopted. Our ...

This dissertation presents research on two low mass X-ray binaries. The eclipsing low-mass X-ray binary 4U 1822-371 is the prototypical accretion disk corona (ADC) system. We have obtained new time-resolved UV spectroscopy with the ACS/SBC on the Hubble Space Telescope and new V- and J-band photometry with the 1.3-m SMARTS telescope at CTIO. We show that ...

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. ...

We study the two-dimensional, time-dependent MHD of radiation-driven winds from luminous accretion disks initially threaded by a purely axial magnetic field. The radiation force is mediated primarily by spectral lines. We use ideal MHD to compute the evolution of Keplerian disks, varying the magnetic field ...

Newly formed stars produce sufficient Lyman continuum luminosity phi to significantly alter the structure and evolution of the accretion disk surrounding them. In the absence of a stellar wind, a nearly static, photoionized, 10^4 K, disk atmosphere, with a scale height that increases with disk ...

Approaching the 14th anniversary of the first observations of GRS 1915+105 with RXTE, we present new results from a joint RXTE/Chandra study of the remarkable X-ray spectral variability of this enigmatic microquasar. For the first time, we are able to show that changes in the broadband X-ray spectrum (RXTE) on timescales of seconds are associated with changes in absorption lines (Chandra HETGS) ...

Nov 9, 2003 ... Consequently accretion disks have fundamental roles in the formation of planets, stars and compact objects, and are the engines driving the ...

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

We propose to study the theory of broad line regions in AGN.We will focus on assessing the role of radiation driven disk winds in producingboth emission and absorption lines. Four key factors motivate our study:{1} the importance of broad lines in AGN spectra and in AGN physics, {2} the wealth and quality of the optical and UV data obtained by HST, {3} the ...

We derive a constraint on the pair density ratio, z(sub +) = n(sub +)/n(sub p), in an electron-positron pair wind flowing away from the central region of an accretion disk around a compact object under the assumption of a coupling between electrons, posit...

Gamma-ray bursts, while rare, may be important contributors to galactic nucleosynthesis. Here we consider the types of nucleosynthesis that can occur as material is ejected from a gamma-ray burst accretion disk. We calculate the composition of material within the disk as it dissociates into protons and neutrons and then use a ...

We have carried out a synthetic spectral analysis of archival IUE of the old nova V841 Oph Lacertae (Nova Oph 1848). The spectrum, obtained with the E140M disperser, reveals a rising continuum shortward of 1560 A, a C IV P-Cygni profile indicative of wind outflow associated with disk accretion, a deep Ly alpha profile, and strong N V ...

These proceedings include papers presented at the Accretion Processes in Astrophysical Systems: Some Like It Hot Conference held in October, 1997 in Maryland, USA. The conference concentrated on the apparent generality of the disk{minus}wind{minus}jet geometry on scales ranging from protostars to the centers of active galactic nuclei. Some of the topics ...

How are accretion disks in Seyfert Galaxies oriented relative to the disk of the spiral galaxy which hosts them? This angle, ?, serves as a link between the innermost workings of the black hole plus fueling accretion disk and the larger galaxy, either as the memory of the activity-provoking ...

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

The standard model of an accretion disk is considered. The temperature in the inner region is computed. It is assumed that the radiated power derives from comptonized photons, produced in a homogeneous single temperature plasma, supported by radiation pre...

Jan 22, 2011 ... Title: The Production of Jets From Magnetized Accretion Disks: Simulation of the Blandford-Payne Mechanism. Authors: Meier, D. ...

Jan 22, 2011 ... Title: The Production of Jets From Magnetic Accretion Disks: Simulation of the Blandford-Payne Mechanism. Authors: Meier, David L. ...

of a collimated jet ejected from the center of the accretion disk. The jet velocity is a strong function of the strength of the initial magnetic field: ...

Feb 23, 2004 ... "Accretion disks are known to flow around many objects in the universe ... Under normal conditions, accretion disks appear far too minute to ...

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

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

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

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

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

Sep 4, 1998 ... In the case of a HMXB with a large ( $\\mathrel{\\hbox{\\rlap{\\hbox{\\lower4pt\\ ) magnetic field the accretion disk cannot extend all the way down to ...