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Accretion disk boundary layers in cataclysmic variables. 1: Optically thick boundary layersWe develop numerical models of accretions disks in cataclysmic variables (CVs), including and emphasizing the boundary layer region where the accretion disk meets the accreting white dwarf. We confine ourselves to solutions where the boundary layer region is vertically optically thick, and find that these solutions share several common features. The angular and radial velocities of the accreting material drop rapidly in a dynamical boundary layer, which has a radial width approximately 1%-3% of the white dwarf radius. The energy dissipated in this region diffuses through the inner part of the disk and is radiated from the disk surface in a thermal boundary layer, which has a radial width comparable to the disk thickness, approximately 5%-15% of the white dwarf radius. We examine the dependence of the boundary layer structure on the mass accretion rate, the white dwarf mass and rotation rate, and the viscosity parameter alpha. We delineate the boundary between optically thick and optically thin boundary layer solutions as a function of these parameters and suggest that by means of a careful comparison with observations it may be possible to estimate alpha in CVs. We derive an expression for the total boundary layer luminosities as a function of the parameters and show that it agrees well with the luminosites of our numerical solutions. Finally, we calcuate simple blackbody continuum spectra of the boundary layer and disk emission for our solutions and compare these to soft X-ray, EUV, and He II emission-line observations of CVs. We show that, through such comparisons, it may be possible to determine the rotation rates of the accreting stars in CVs, and perhaps also the white dwarf masses and the accretion rates. The spectra are quite insensitive to alpha, so the uncertainty in this parameter does not affect such comparisons.
Document ID
19950054926
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Popham, Robert
(Univ. of Illinois at Urbana-Champaign, Urbana, IL United States)
Narayan, Ramesh
(Harvard-Smithsonina Center for Astrophysics, Cambridge, MA United States)
Date Acquired
August 16, 2013
Publication Date
March 20, 1995
Publication Information
Publication: The Astrophysical Journal, Part 1
Volume: 442
Issue: 1
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A86525
Funding Number(s)
CONTRACT_GRANT: NSF AST-91-48279
CONTRACT_GRANT: NAGW-1583
CONTRACT_GRANT: NSF AST-93-15133
CONTRACT_GRANT: NSF PHY-91-00283
Distribution Limits
Public
Copyright
Other

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