Terminal velocities of Wolf–Rayet winds from infrared He I lines

We have observed 1- and 2-μm spectra covering the He I 2s–2p triplet and singlet lines in a sample of Wolf-Rayet stars. Most of the He I lines have P Cygni profiles, which are fitted using the SEI (Sobolev with exact integration) method to derive terminal velocities. From our observations of 41 star...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 1994-08, Vol.269 (4), p.1082-1098
Main Authors: Eenens, P. R. J., Williams, P. M.
Format: Article
Language:English
Subjects:
binaries: spectroscopic
infrared: stars
line: profiles
stars: mass-loss
stars: Wolf-Rayet
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Summary:We have observed 1- and 2-μm spectra covering the He I 2s–2p triplet and singlet lines in a sample of Wolf-Rayet stars. Most of the He I lines have P Cygni profiles, which are fitted using the SEI (Sobolev with exact integration) method to derive terminal velocities. From our observations of 41 stars, the He I velocities are only about 70 per cent of those measured at the violet edges of the P Cygni profiles of the C IV and Si IV resonance lines, but are in good agreement with those measured at the greatest displacements of the saturated absorption troughs in these lines (νblack). We discuss the advantages of the infrared method, and also the influence of binarity on the relation between the measured displacement velocities and the stars' terminal wind velocities. For 18 stars not accessible to the IUE, these are the first accurate values for the terminal velocities of their winds. The analysis of the He I profiles reveals differences in the radial structure of the winds between stars of the same subtype and having similar terminal velocities.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/269.4.1082