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Record Details

Record 26 of 779
Why DA and DB white dwarfs do not show coronal activity and p-mode oscillations
External Online Source: doi:10.1086/168023
Author and Affiliation:
Musielak, Z. E.(NASA Marshall Space Flight Center, Huntsville, AL, United States)
Fontenla, J. M.(NASA Marshall Space Flight Center, Huntsville, AL, United States)
Abstract: The problems of nonradiative heating of outer atmospheric layers and p-mode oscillations in white dwarfs caused by acoustic waves generated in convective zones are discussed. These effects have been studied by calculating the cutoff periods for adiabatic and isothermal waves propagating in atmospheres of DA and DB stars with Teff greater than or equal 20,000 K and log g = 6-9. The obtained cutoff periods are approximately bounded by 0.01 and 40 sec for high- and low-gravity white dwarfs, respectively. Expected amplitudes of p-mode oscillations corresponding to trapped acoustic waves with small angular wave numbers are estimated, indicating that the amplitudes could be observed as Doppler shifts of spectral lines which might be detectable if adequate spectral resolution were available. The luminosity variations corresponding to these amplitudes are unlikely to be observable when all damping processes are accounted for. Results also indicate that the present theory of convection predicts some irregularities in the behavior of physical parameters.
Publication Date: Nov 01, 1989
Document ID:
19900026013
(Acquired Nov 28, 1995)
Accession Number: 90A13068
Subject Category: ASTROPHYSICS
Document Type: Journal Article
Publication Information: Astrophysical Journal, Part 1 (ISSN 0004-637X); 346; 435-443
Publisher Information: United States
Financial Sponsor: NASA; United States
Organization Source: NASA Marshall Space Flight Center; Huntsville, AL, United States
Description: 9p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: STELLAR ATMOSPHERES; STELLAR CORONAS; STELLAR OSCILLATIONS; WAVE PROPAGATION; WHITE DWARF STARS; SOUND WAVES; STELLAR ACTIVITY; VIBRATION MODE
Imprint And Other Notes: Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 346, Nov. 1, 1989, p. 435-443. Research supported by the Universities Space Research Association.
Miscellaneous Notes: Research supported by the Universities Space Research Association
Availability Source: Other Sources
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