UNIFORMITY OF THE WC STARS IN THE LARGE MAGELLANIC CLOUD

Uniformity of the WC stars in the LMC is investigated. It is a tenable hypothesis that (b - u)0 is the same for all stars, and this enables estimates of absorption in the 30 Dor region where local irregularities are large. With absorption corrections based on (b - v)0 = -0.30, we find that the flux in the C IV λ5808 line is the same for all the WC stars observed in the LMC; log ∫λ (total, ergs cm-2 s-1) = -11.0 ± 0.15, corresponding to log ∫λ (total, ergs s-1) = 36.5 for (m - M)0 = 18.5 mag. The scatter may be mostly observational, and the stars could be useful standard candles if WC4 stars in other galaxies are the same. The line flux ratio (λ5808/ A4650) = -0.22 ± 0.1 dex and can be used to determine reddening. Constant line flux suggests constant flux at the UV wavelengths responsible for C IV ionization. The large range of observed v magnitudes is probably a result of the presence of companions (either physically related or just unresolved). The width of the A5808 line is less than that of the A4650 line in WC4 stars and greater in the WO stars. The width ratio correlates with line width; the combination of width and width ratio provides a simple diagnostic for the WO stars. The use of Wolf-Rayet star emission-line fluxes for reddening and distance determination (if the method proves reliable) has a great advantage over other techniques. The method involves measuring fluxes that are 1-4 mag brighter than those in the continuum of a WR star and which are independent of contamination by the continuum of a companion (physically related or just unresolved); the broad lines stand out clearly even at low spectral resolution.