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Origin of the DA and non-DA white dwarf starsVarious proposals for the bifurcation of the white dwarf cooling sequence are reviewed. 'Primordial' theories, in which the basic bifurcation of the white dwarf sequence is rooted in events predating the white dwarf stage of stellar evolution, are discussed, along with the competing 'mixing' theories in which processes occurring during the white dwarf stage are responsible for the existence of DA or non-DA stars. A new proposal is suggested, representing a two-channel scenario. In the DA channel, some process reduces the hydrogen layer mass to the value of less than 10 to the -7th. The non-DA channel is similar to that in the primordial scenario. These considerations suggest that some mechanism operates in both channels to reduce the thickness of the outermost layer of the white dwarf. It is also noted that accretion from the interstellar medium has little to do with whether a particular white dwarf becomes a DA or a non-DA star.
Document ID
19900045698
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Shipman, Harry L.
(Delaware, University Newark, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1989
Subject Category
Astrophysics
Meeting Information
Meeting: IAU Colloquium
Location: Hanover, NH
Country: United States
Start Date: August 15, 1988
End Date: August 19, 1988
Accession Number
90A32753
Funding Number(s)
CONTRACT_GRANT: NAG5-972
CONTRACT_GRANT: NAG5-348
CONTRACT_GRANT: NSF AST-87-20530
Distribution Limits
Public
Copyright
Other

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