2000MNRAS.314...23W

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 WR69 (HD136488) and WR104 (Ve2-45). Comparison of spectra of WR104 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 Oii line strengths. The only two WC9 stars in the observed sample that do not make circumstellar dust, WR81 (He3-1316) and WR92 (HD 157451), are found to have anomalously weak Oii and strong Heii 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.