Centrifugal barriers in magnetospheric accretion

Abstract

We reconsider the dynamics of accretion flows onto magnetized central star. For dipolar magnetically aligned case, the centrifugal barrier is at $R_{cb}=(2/3{)}^{1/3}{R}_c=0.87R_c$, where $R_c=(GM/{\Omega }^2{)}^{1/3}$ is the corotation radius. For oblique dipole direct accretion from the corotation radius $R_c$ is possible only for magnetic obliquity satisfying $\tan {\theta }_{\mu }\ge 1/(2\sqrt{3})$ (${\theta }_{\mu }\ge 16.1^{\circ }$). The accretion proceeds in a form of funnel flows - along two streams centered on the $\mu -\Omega$ plane, with azimuthal opening angle $\cos (\Delta \varphi )={\cot }^2{\theta }_{\mu }/12$. For the magnetosphere distorted by the diamagnetic disk, the centrifugal barrier can be at as small radius as $R_{cb}=0.719R_c$ for the fully confined dipole, extending out to $R_{cb}\sim R_c$ for the magnetically balanced case. Type-II X-ray bursts in accreting neutron stars may be mediated by the centrifugal barrier; this requires nearly aligned configuration. Centrifugally-barriered material trapped in the magnetosphere may lead to periodic obscuration ("dips") in the light curve of the host star, e.g., as observed in accreting young stellar objects and X-ray binaries.

References in corpus (6)

• Theory of Star Formation
• Magnetic White Dwarfs
• Accretion funnels onto weakly magnetized young stars
• A population study of type II bursts in the Rapid Burster
• Accreting strongly magnetised neutron stars: X-ray Pulsars
• Inertial oscillation modes of an inclined dipolar magnetosphere as a source of band-limited noise in X-ray pulsars

Cited by in corpus (4)

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• X-ray spectroscopy method of white dwarf mass determination in intermediate polars. External systematic uncertainties
• Deciphering Accretion-Driven Starquakes in Recycled Millisecond Pulsars using Gravitational Waves