A discrete-time model for inhomogeneous spherical accretion onto neutron stars

Journal Article · Tue May 01 04:00:00 EDT 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/168718· OSTI ID:6711648

Demmel, V; Morfill, G; Atmanspacher, H ^[1]

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1. Max-Planck-Institut fuer Physik und Astrophysik, Garching (Germany, F.R.)

This paper presents a phenomenological model for accreting neutron stars at high mass accretion rates. The optically thick infalling plasma and the outgoing radiation are described as two interfacing fluids in the gravitational field of the compact star. The strong interaction of the fluids causes the mass and radiation flow to be highly inhomogeneous. It is assumed that the plasma is trapped in large localized clumps arising through a Rayleigh-Taylor instability at the boundary between the fluids near the neutron star surface. The radiation created through the impact of the clumps on the surface is assumed to form bubbles of approximately the same size. The high-energy density of the bubbles is sufficiently large to push the matter above them out, creating channels in the plasma flow. The interaction between the two fluids can be described in time-discrete evolution equations of the clumps, bubbles, and channels. When this is combined with the 'average' continuity equations for the mass, energy, and momentum for this highly inhomogeneous accretion scenario, the luminosity of the neutron star can be calculated as a function of the mass accretion rate. This calculation shows that, for large mass accretion rates, luminosities substantially exceeding the Eddington limit can be obtained. 24 refs.

• OSTI ID: 6711648
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 354; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
FLUID MECHANICS
GRAVITATION
GRAVITATIONAL FIELDS
HYDRODYNAMICS
INSTABILITY
MAGNETOHYDRODYNAMICS
MATHEMATICAL MODELS
MECHANICS
NEUTRON STARS
RAYLEIGH-TAYLOR INSTABILITY
STABILITY
STAR ACCRETION
STAR EVOLUTION
STAR MODELS
STARS
STELLAR RADIATION