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Puzzling problems of He I line formation in early B stars

Published online by Cambridge University Press:  26 May 2016

Myron A. Smith ,
Ivan Hubeny  and
Thierry Lanz
Myron A. Smith
Affiliation:
IUE/CSC Observatory, 10000A Aerospace Rd., Lanham-Seabrook MD 20706, USA
Ivan Hubeny
Affiliation:
Goddard Space Flight Center, Greenbelt, MD 20771, USA
Thierry Lanz
Affiliation:
Goddard Space Flight Center, Greenbelt, MD 20771, USA

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Although NLTE model atmospheres have been shown to resolve most of the equivalent width (EW) discrepancies for blue He I lines (Auer and Mihalas 1972, 1973), Wolff and Heasley (1984, 1985) have demonstrated that discrepancies remain for the leading members of the singlet/triplet 2P – nD series, viz. λ6678 and λ5876. These two lines are the strongest nonresonance He I transitions and are important because they respond to thermal changes in the superficial atmosphere (τ~ 10-3) of early B stars. In order to understand the observed rapid variations of the λ6678 line in mild Be stars, we undertook a survey of EWs of λ6678 and λ4388, namely the first and third member of the same series. These two lines have a log gf ratio of 15 but have similar EWs in B star spectra. Our new observations confirm the red line discrepancy noted by WH85 and point to additional EW differences among various groups of B stars not noted hitherto.

Type
5. Be Stars: Spectroscopy and Photometry
Information
Symposium - International Astronomical Union , Volume 162: Pulsation, Rotation and Mass Loss in Early-Type Stars , 1994 , pp. 273 - 274
Copyright
Copyright © Kluwer 1994 

References

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Wolff, S., and Heasley, J. 1985, ApJ, 292, 589, (“WH85”) Google Scholar