Accretion Flows in Galactic X-Ray Sources. Optically Thin Spherically Symmetric Model

Buff, J.; McCray, Richard

doi:10.1086/152780

Cited by 42 publications

(25 citation statements)

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“…There, the gas pressure and its selfgravity have been ignored and the analysis is purely Newtonian. The work of Buff & McCray (1974) is dedicated to a similar problem. Later researchers included both gas pressure and selfgravity (Okuda & Sakashita 1977;Maraschi et al 1978;Chia 1978Chia , 1979Grindlay 1978).…”

Section: The Shakura Modelmentioning

confidence: 99%

Luminosity, selfgravitation and nonuniqueness of stationary accretion

Karkowski¹,

Roszkowski²

2007

A&A

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Aims. We show the existence of two branches of solutions bifurcating from a point with maximal luminosity. Methods. We investigate a Newtonian description of accreting compact bodies with hard surfaces, including luminosity and selfgravitation of polytropic perfect fluids. This nonlinear integro-differential problem is studied numerically. Its reduced version simplifies (under appropriate boundary conditions) to an algebraic relation between luminosity and the gas abundance in stationary, spherically symmetric flows and it can be dealt with analytically.Results. There exist -for a given luminosity, asymptotic mass and asymptotic temperature -two sub-critical solutions that bifurcate from an extremal point. They differ by the fluid content and the mass of the compact centre. Their relevance to Thorne-Żytkow stars is discussed.

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Section: The Shakura Modelmentioning

confidence: 99%

Luminosity, selfgravitation and nonuniqueness of stationary accretion

Karkowski¹,

Roszkowski²

2007

A&A

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“…As noted by Buff & McCray (1974), if stellar radiation substantially increases the ionization degree of trace elements by the photoionization process, the radiative cooling rate can be lower than in the purely collisional case. For the sake of comparison, we shall also present the results of calculations on the basis of an appropriate cooling function (Stellingwerf & Buff 1982): , and E = 0.1 (Var4).…”

Section: Quasi-spherical Accretion Onto the Magnetospherementioning

confidence: 98%

“…Spherical accretion onto compact X-ray sources with preheating of matter was studied by Buff & McCray (1974), Ostriker et al (1976), Cowie et al (1978Cowie et al ( , 1981, Bisnovatyi-Kogan & Blinnikov (1980, further on cited as BKB), and Stellingwerf & Buff (1982). It was shown that if the accretion flow in the presence of radiative effects has properties similar to the Bondi flow (the sonic temperature T s is of the order of the recombination temperature and ρ s ≈ ρ ∞ ), then for accretion efficiencies E > E cr steady accretion becomes impossible, provided that L > L cr ≈ 10 −3 × 10 −2 × L Edd , where L Edd is the Eddington luminosity.…”

Section: For Finite Accretor Sizesmentioning

confidence: 99%

“…There are several available in the literature (Cox & Tucker 1969;Buff & McCray 1974;Raymond et al 1976;Stellingwerf & Buff 1982;Cowie et al 1981;Bond et al 1984;Nobili et al 1991;Sutherland & Dopita 1993;Hutchings & Thomas 2000). The difference among the functions is not only in different approximations of available calculated data.…”

Section: Quasi-spherical Accretion Onto the Magnetospherementioning

confidence: 99%

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The influence of radiative effects on the accretion onto stellar magnetospheres

Kryukov

Pogorelov

Anzer

et al. 2003

A&A

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Abstract. The influence of radiative effects on the accretion onto stellar magnetospheres is investigated by performing global 2-and 2.5-dimensional simulations on the basis of high-resolution numerical schemes with the application of irregular grids adapted to the shape of the magnetopause. The latter is represented by an impermeable, contracted dipole magnetic field surface with polar holes. Accreting matter is assumed to be optically thin. The physical mechanisms which are taken into account include cooling due to free-free and free-bound transitions, the Compton heating via X-ray scattering on electrons, and the inverse Compton cooling in the regions where the temperature of the matter becomes sufficiently large to be able to transfer part of its internal energy to photons. Depending on the determining parameters, both steady-state solutions with a system of discontinuities and unsteady flows with expanding shock waves can be obtained. It is shown that efficient cooling of the matter can substantially facilitate the penetration of the matter through the polar holes. The detailed consideration of the realistic radiative effects proved to be of great importance in our understanding of the accretion phenomenon, since they can substantially affect it both qualitatively and quantitatively.

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“…X-ray irradiated gas is subject to a thermal instability in the 10 5 -10 6 K temperature range [224] [225], suppressing X-ray line emission in that regime. Application of the Field stability criterion [226] indicates that a photoionized gas may become unstable when recombination cooling of H-like and Helike ions is important.…”

Section: Thermal Instabilitymentioning

confidence: 99%

Atomic X-ray spectroscopy of accreting black holes

Liedahl¹,

Torres²

2005

Can. J. Phys.

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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 rather distinct regimes of physical conditions and geometric scale. X-ray emission probes the innermost regions of the accretion disk, where relativistic effects prevail. While this has been known for decades, it also has been acknowledged that inferring physical conditions in the relativistic regime from the behavior of the X-ray continuum is problematic and not satisfactorily constraining. With the discovery in the 1990s of iron X-ray lines bearing signatures of relativistic distortion came the hope that such emission would more firmly constrain models of disk accretion near black holes, as well as provide observational criteria by which to test general relativity in the strong field limit. Here we provide an introduction to this phenomenon. While the presentation is intended to be primarily tutorial in nature, we aim also to acquaint the reader with trends in current research. To achieve these ends, we present the basic applications of general relativity that pertain to X-ray spectroscopic observations of black hole accretion disk systems, focusing on the Schwarzschild and Kerr solutions to the Einstein field equations. To this we add treatments of the fundamental concepts associated with the theoretical and modeling aspects of accretion disks, as well as relevant topics from observational and theoretical X-ray spectroscopy. PACS Nos.: 32.30. Rj, 32.80.Hd, 95.30.Dr, 95.30.Sf, 95.85.Nv, 97.10.Gz. 97.80.Jp, 98.35.Mp, 98.62.Mw

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Accretion Flows in Galactic X-Ray Sources. Optically Thin Spherically Symmetric Model

Cited by 42 publications

References 0 publications

Luminosity, selfgravitation and nonuniqueness of stationary accretion

Luminosity, selfgravitation and nonuniqueness of stationary accretion

The influence of radiative effects on the accretion onto stellar magnetospheres

Atomic X-ray spectroscopy of accreting black holes

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