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Record 41 of 5363
Chemical stratification in white dwarf atmospheres and envelopes
Author and Affiliation:
Koester, D.(Louisiana State University, Baton Rouge, United States)
Abstract: Theoretical arguments supporting a new mechanism maintaining a homogeneously mixed composition in white dwarf atmospheres with traces of helium are presented. Diffusion time scales, meridional circulation, mass loss, accretion of interstellar matter, convection, and radiative levitation are discussed. Theoretically, layered envelopes, with hydrogen on top of helium and an abundance profile in the transition layer determined by diffusion equilibrium, are expected. In cases with observed helium and hydrogen in the atmosphere this means that the total hydrogen mass must be very small. The empirical evidence for such atmospheres are assessed, using a new grid of model atmospheres with stratified element abundances and applying it to typical mixed abundance cases at the hot end of the white dwarf temperature sequence.
Publication Date: Jan 01, 1989
Document ID:
19900045697
(Acquired Nov 28, 1995)
Accession Number: 90A32752
Subject Category: ASTROPHYSICS
Document Type: Conference Paper
Publication Information: (SEE A90-32719)
Publisher Information: Germany
Meeting Information: IAU Colloquium; 114th; Aug. 15-19, 1988; Hanover, NH; United States
Contract/Grant/Task Num: NAG5-990
Financial Sponsor: NASA; United States
Organization Source: Louisiana State Univ.; Baton Rouge, LA, United States
Description: 14p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: ATMOSPHERIC STRATIFICATION; HELIUM HYDROGEN ATMOSPHERES; STELLAR ATMOSPHERES; STELLAR ENVELOPES; WHITE DWARF STARS; ATMOSPHERIC CHEMISTRY; CHEMICAL COMPOSITION; ELECTRIC FIELDS; GASEOUS DIFFUSION; GRAVITATIONAL FIELDS
Imprint And Other Notes: IN: White dwarfs; Proceedings of IAU Colloquium 114th, Hanover, NH, Aug. 15-19, 1988 (A90-32719 13-90). Berlin and New York, Springer-Verlag, 1989, p. 206-219.
Availability Source: Other Sources
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