Ultraviolet spectral morphology of on and OC stars
Symposium - International astronomical union
We have undertaken a systematic survey of 115 0-B0 type spectra between 1200 and 1900å, by means of International Ultraviolet Explorer high-dispersion data rebinned to a constant wavelength resolution of 0.25å and uniformly normalized (Walborn and Panek 1983). The ultraviolet spectral features, both photospheric and stellar wind, are found to be smoothly correlated with the optical spectral types for the majority of normal stars. In particular, the C IV (λλ1548,1551) and N V (λλ1239,1243)
... (λλ1239,1243) resonance doublets show similar strong P Cygni profiles, which decline along the main sequence beginning at type 07 but remain strong in all higher luminosity spectra. In contrast, the stellar wind effect in the Si IV (λλ1394,1403) doublet displays a pronounced luminosity dependence, being absent from the main sequence spectra at all types and developing gradually through the intermediate luminosity classes into a full P Cygni profile in the supergiants. Relative to this consistent framework provided by the normal stars, a number of peculiar spectra can be succinctly described, including several of types OBN and OBC (Walborn 1976).