Non-LTE modelling of the He I 10830 Å line in early-type main sequence stars

Dr. Remeis-Sternwarte Bamberg, Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany e-mail: przybilla@sternwarte.uni-erlangen.de

Received: 12 May 2005
Accepted: 3 July 2005

Abstract

The near-IR  10 830 Å transition is a highly sensitive diagnostic for non-LTE effects in astrophysical plasmas. So far, non-LTE line-formation computations have failed to quantitatively reproduce observations of this line in the entire range of early-A to late-O main sequence stars. It is shown that the non-LTE modelling was insufficient, for the most part, either because of inaccurate photoionization cross-sections for the 2s ³S state or because of neglecting line blocking. New calculations based on state-of-the-art atomic data give excellent agreement with observation for the  10 830 Å feature, while profiles of the lines in the visual are retained.