Mass-loss rates and C/He ratios in the winds of the WC central stars of planetary nebulae

We estimate the C/He ratio in the central star winds of five planetary nebulae that have WC spectra: SwSt–l, He2–99, He2–113, BD + 30°3639 and NGC 5315. These estimates take into account optical depth effects in the wind. Our results indicate that 0.41 < C/He < 0.68 by number, suggesting exposure of He-burned material. If helium and carbon are the dominant elements in the winds of those stars, the mass-loss rates are in the range 5.7 × 10–7 to 6.7 × 10–6 M⊙ yr–1, substantially higher than previous estimates.