Spectroscopy of WC9 Wolf-Rayet stars: a search for companions

A spectroscopic search for luminous companions to WC9-type Wolf-Rayet stars making circumstellar dust reveals the presence of absorption lines attributable to companions in the blue spectra of WR 69 (HD 136488) and WR 104 (Ve2-45), Comparison of spectra of WR 104 observed in 1995 and 1997 showed the absorption lines to be more conspicuous in the latter observation and the emission lines weaker, suggesting a selective eclipse of the WC9 star similar to that observed by Crowther in 1996, The WC9 emission-line spectra are shown to be less uniform than previously thought, showing a significant range of O II line strengths. The only two WC9 stars in the observed sample that do not make circumstellar dust, WR 81 (He3-1316) and WR 92 (HD 157451), are found to have anomalously weak O II and strong Heir lines. We suggest that these spectroscopic differences may reflect a compositional difference that plays a role in determining which of the WC9 stars make dust.