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J.L. Fisker, D. Balsara (University of Notre Dame)
For a weakly magnetized white dwarf with a thin accretion disk, the matter impacts near the equator and spreads out as new matter continuously piles up behind it. In a scenario proposed and investigated analytically by Piro & Bildsten (2004) for the white dwarf case and Inogamov and Sunyeav (1999) for the neutron star case, viscous forces slow down the accreted matter from its Keplerian velocity as it moves towards the pole and eventually comes into corotation with the stellar surface at a lattitude, \theta. The viscous dissipation of the rotational energy heats the material, which gives rise to a radiating hot band of material on either side of the disc, which adds an extra component to the luminosity spectrum depending on \theta.
In this paper we present preliminary calculations of an alpha-disk and investigate the size of the spreading layer and the effect of differential rotation and vertical mixing as the matter spreads and settles on the star.
[1] Piro, A., & Bildsten, L.~2004, ApJ. 610, 977
[2] Inogamov, N.A., & Sunyeav, R.A.~1999, Astron. Lett., 25, 269
This work has been performed through the Joint Institute of Nuclear Astrophysics (http://www.JINAweb.org) under NSF-PFC grant PHY02-16783
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.