P Cygni profile

He I, He II, [0 III] and [s VIIl] lines continue to increase on day 629. Another noticeable feature is the well marked P Cygni profile of C IV (770.9 and 772.6 nm). The absorption component is displaced by -3000 lem/s. It indicates a strong stellar wind leading to a high mass loss rate. Such a velocity has already been found for the C IV ions in the resonance doublet of C IV at 154.8 - 155 nm in Nova HR Del. 

FIGURE 18 Illustration of the formation of a P Cygni profile (emission line near the rest wavelength, with blue-shifted absorption) in a spectral feature, resulting from high-velocity outflow of gas from a stellar atmosphere. 

At early times the spectra of supemovae exhibit a contimium upon which are superimposed lines exhibiting P-Cygni profiles. Hie line velocities measured from the absorption trough in their P-Cygni profiles correspond to radial distances within the ejecta and are therefore a powerful tool in investigating the composition of the outer envelope of a supernova. 

After the imtial discovery of about 11 Hel emission line stars (Krabbe et al. 91) a new data-cube with mudi improved S/N and about twice the spatial resolution ( 1" FWHM at 0.5"/pixel) has been obt2uned at the WHT, La Palma, revealing now 15 to 18 Hel emitting stars (Fig. 2). These stars seem to be related to the class of Luminous Blue Variables (LBV) indicated by their brightness, strong, broad Hel and H emission lines and the absence of HeH, C, or N NIR emission lines which would be indicators of WN stars. Despite their common nature, the members show differences in Hel/Bry, Hel (2.06/ian)/HeI(2.11 ), Line/continuum, brightness, and the depth of the P-Cygni profile. 

It is easily seen that there must be a discontinuity in slope of the P-Cygni line profiles at a frequency corresponding to the velocity of the matter at the photosphere, if the photosphere is sharp. However, as Branch (1980) has shown, this discontinuity is most easily observed if the line Sobolev optical depth Tjj <5, in which case the break appears at the frequency of maximum absorption. Using the results of Blanco et al. (1987) and Phillips (1987) [assuming that the LMC velocity had been removed], we do indeed find that the weakest lines (Fell X5018, Fell X5169,... 

---