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Observational knowledge about the physical properties of O starsInformation about the effective temperatures, radii, and masses of O-type stars is presented. It is argued that rapid variations in the amount of light from O stars and the spectral distribution are a result chiefly of changes which occur in the envelope of the star. The stability of the photospheric layers of O stars against convection is reviewed and it is noted that late O stars and early B stars have a convection zone in the deeper parts of the photosphere. This convection zone is due to the second ionization of helium. Evidence is reviewed that most of the line-profile changes seen for O stars are generated by changes in the physical state of the mantle of the star, that is of the outer atmosphere where the deposition of non-radiative energy and momentum controls the physical state of the atmosphere. The physical state of the mantle may change in response to changes in the upper envelope of a star with a different time constant than the photosphere does.
Document ID
19850053851
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Underhill, A. B.
(NASA Goddard Space Flight Center Laboratory for Astronomy and Solar Physics, Greenbelt, MD, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1983
Publication Information
Publication: Hvar Observatory, Bulletin
Volume: 7
Issue: 1, 19
ISSN: 0351-2651
Subject Category
Astrophysics
Accession Number
85A36002
Distribution Limits
Public
Copyright
Other

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