Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-06-21
Astrophys.J. 609 (2004) 1181
Astronomy and Astrophysics
Astrophysics
34 pages, 14 figures, 4 tables
Scientific paper
10.1086/421316
We discuss aspects of non-LTE line formation for hydrogen in early-type stars. We evaluate the effect of variations in the electron-impact excitation cross sections in model atoms of differing complexity by comparison with observation. While the Balmer lines are basically unaffected by the choice of atomic data, the Paschen, Brackett and Pfund series members allow us to discriminate between the different models. Non-LTE calculations based on the widely-used approximation formulae of Mihalas, Heasley & Auer and of Johnson fail to simultaneously reproduce the optical and IR spectra over the entire parameter range. The use of data from ab-initio calculations up to principal quantum number n<=7 largely solves the problem. We recommend a reference model using the available data. This model is of general interest because of the ubiquity of the hydrogen spectrum.
Butler Keith
Przybilla Norbert
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