2007AJ....134.1380M

The UV spectra of all ``weak emission line central stars of planetary nebulae'' (WELSs) with available IUE data are presented and discussed. We performed line identifications and equivalent-width and flux measurements for several features in the spectra. We found that the WELSs can be divided into three different groups regarding their UV spectra: (1) strong P Cygni profiles (mainly in C IV λ1549), (2) weak P Cygni features, and (3) absence of P Cygni profiles. The last group encompasses stars with a featureless UV spectrum or with intense emission lines and a weak continuum, which are most likely of nebular origin. We have measured wind terminal velocities for all objects presenting P Cygni profiles in N V λ1238 and/or C IV λ1549. The results obtained were compared to the UV data of the two prototype stars of the [WC]-PG 1159 class, namely, A30 and A78. For WELSs presenting P Cygni features, most of the terminal velocities fall in the range of ∼1000-1500 km/s, while [WC]-PG 1159 stars possess much higher values, of ∼3000 km/s. The [WC]-PG 1159 stars are characterized by intense, simultaneous P Cygni emissions in the ∼1150-2000 Å interval of N V λ1238, O V λ1371, and C IV λ1549. In contrast, we found that O V λ1371 is very weak or absent in the WELS spectra. On the basis of the UV spectra alone, our findings indicate that [WC]-PG 1159 stars are distinct from the WELSs, contrary to previous claims in the literature.