DISTANCES OF GALACTIC WC STARS FROM EMISSION-LINE FLUXES AND A QUANTIFICATION OF THE WC CLASSIFICATION

WC stars belonging to Galactic open clusters and associations are used to calibrate the flux in the C IV λ5808 emission line. WC5-7 stars all show the same flux within the (considerable) errors, with log [F λ(5808)/ergs s-1 cm-2] = -8.1 ± 0.2, reduced to a distance of 1 kpc, 0.5 dex fainter than for WC4 stars in the LMC. The line fluxes for WC8 and 9 stars are probably lower again. All stars with reddening derived from (b-v) colors are used to calibrate the reddening-free flux ratio of the two strong lines λ5808/λ4650. It is relatively insensitive to subclass; the values range from -0.22 ± 0.08 dex for WC4 stars to -0.56 ± 0.05 dex for WC9 stars. Distances of Galactic WC stars are derived based on these values. Differences from previous estimates are discussed. The method is independent of whether the star is a binary or blended with a close companion. For nearby stars, the accuracy of the line-flux method vis-à-vis the Mv, b-v method is presently inferior. However, for distant stars where resolution often becomes a problem, the continuum flux method breaks down, while the line flux method still works. A quantification of the classification system for WC stars is suggested which is entirely compatible with the existing scheme and which provides unambiguous definition of the subtype in all cases. Ten stars are reclassified to fit the new definition.