Spectroscopic studies of O-type stars. IV. Lines in the red region.
Abstract
Equivalent widths of several lines in the red spectral region have been obtained for 77 0 and Of type stars. The spectroscopic material of 1 6A mm ' dispersion, in some cases using a fiber-optics image tube, was obtained at the Lick Observatory 120-inch (3-m) coude'. Comparison with the non-LTE plane-parallel models of Auer and Mihalas has been made. The strengths of the lines A6678 He I and A541 1 He ii are in good agreement with their models for most stars. For main-sequence stars the line A5876 He I is about 30 percent stronger than predicted and is even more discrepant for supergiants This is most likely due to the effect of microturbulence which has not been included in the models. For main-sequence stars there is good agreement between the observations and the models for Ha. For many luminous stars this line has a P Cygni profile or is strongly in emission. There is a good correlation between these extended-atmosphere effects for Ha and for A4686 He ii. Runs of observed equivalent width with spectral type for A5801 C iv and A5592 0 iii are also presented. There is evidence that some supergiant stars have excessively strong C iv lines, in agreement with the OC classifications of Walborn. There is also strong evidence that these lines are variable in at least one case. Subject headings: atmo, ste)lar - early-type stars - luminous stars - Of-type stars -
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1974
- DOI:
- 10.1086/152664
- Bibcode:
- 1974ApJ...187..539C