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The threshold for stellar winds in hot main-sequence starsThe profiles of ultraviolet resonance lines of C IV were surveyed in a sample of 29 cluster and association members in the spectral type range O9-B2 III-V, together with a few field stars of interest. The temperatures and gravities of the stars were taken from the model atmosphere analysis by Grigsby, Morrison, & Anderson (1992), and the luminosities were estimated on the basis of cluster and association distances from the recent literature. A parameter P(sub w) was defined in order to describe the degree and assymetry of the C IV profile. This parameter, together with total C IV equivalent width, was found to be well correlated with stellar luminosity and temperature. A few anomalous stars were noted: tau Sco, HD 66665, HD 13621, and the ON stars HD12323 and HD 201345. The results suggest a sudden onset of observable mass loss at T(effective) = 27,500 +/- 500 K, log (L/solar luminosity) = 4.4 +/- 0.12, in agreement with the previous study by Prinja (1989). At T(effective) = 28,000 K and log g = 4, our non-LTE model atmospheres show an enhancement in the ground-state population of C(+3) in their topmost layer, which could be responsible for initiation of the winds via radiation pressure on the C(+3) ions, or for the onset of visibility of C(+3) ions in the wind because of an increase in the optical depth in the C IV lines in the outermost layers.
Document ID
19950046458
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Grigsby, James A.
(Wittenberg Univ. Springfield, OH, United States)
Morrison, Nancy D.
(Univ. of Toledo, Toledo, OH United States)
Date Acquired
August 16, 2013
Publication Date
April 1, 1995
Publication Information
Publication: Astrophysical Journal
Volume: 442
Issue: 2 Pa
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A78057
Funding Number(s)
CONTRACT_GRANT: NAG5-979
CONTRACT_GRANT: NAG5-970
CONTRACT_GRANT: NAG5-253
Distribution Limits
Public
Copyright
Other

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