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Astron. Astrophys. 330, 306-310 (1998)

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Visible neutral helium lines in main sequence B-type stars:
observations and NLTE calculations

F. Leone 1 , * and A.C. Lanzafame 2

1 Osservatorio Astrofisico di Catania, Città Universitaria, I-95125 Catania, Italy
2 Istituto di Astronomia, Città Universitaria, I-95125 Catania, Italy

Received 15 July 1997 / Accepted 20 October 1997

Abstract

Spectra in the visible range 410 - 710 nm have been obtained for a sample of main sequence B-type stars to determine the behavior of neutral helium lines with effective temperature and gravity. Equivalent widths have been compared with new calculations which combine the capabilities of LTE atmospheric models of including millions of lines contributing to the opacity and accurate NLTE treatment of the line formation. The latter take advantage of accurate atomic cross-sections. We find a satisfactory agreement between theory and observations with differences probably due to the microturbulence.

We also investigate the effects of blending and find that the HeI 412.1 nm is severely blended with oxygen lines for spectral types earlier than B3.

Key words: line: formation – stars: abundances – stars: early-type

* Visiting astronomer, Complejo Astrónomico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigationes Cientifcas y Técnicas (CONICET) and the National Universities of La Plata, Córdoba and San Juan

Send offprint requests to: F. Leone

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© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998
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