Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...442..794g&link_type=abstract
Astrophysical Journal (ISSN 0004-637X), vol. 442, no. 2, Part 1, p. 794-811
Astronomy and Astrophysics
Astronomy
10
Hot Stars, Main Sequence Stars, Sky Surveys (Astronomy), Stellar Luminosity, Stellar Spectra, Stellar Temperature, Stellar Winds, Ultraviolet Spectra, Hertzsprung-Russell Diagram, Resonance Lines, Spectrum Analysis
Scientific paper
The 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 Pw 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.
Grigsby James A.
Morrison Nancy D.
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