THE EFFECT OF BINARITY AND METALLICITY IN THE SPECTRA OF WC AND W0 STARS

statistical analysis of the main emission lines common to the WC and WO stars is made based on an extensive set of spectral data. To define the trends in equivalent width ( Wλ), line ratios, and line widths, median values are derived for single-spectrum stars of different spectral class. We find that in Galactic WO and WC4 stars, Wλ (C IV 581 nm) is smaller compared to in extragalactic objects. In both Galactic and extragalactic stars, Wλ (O V 559 nm) smoothly increases towards early WC and WO stars. It is argued that differences in stellar wind structure, in combination with the ambient metallicity, may be the cause of the anomalies. Variation of the profile of the 465 nm blend indicates a substantial contribution of He II 468 nm for the WCE and WO stars. In addition, we comment on the carbon abundances in relation to the evolutionary status of these objects. We also give an estimate of the OB/WR continuum flux ratio in composite-spectrum systems.