  Hydrogen-deficient Wolf-Rayet (WR) stars are potential candidates of Type
Ib/Ic supernova (SN Ib/Ic) progenitors and their evolution is governed by mass
loss. Stellar evolution models with the most popular prescription for WR
mass-loss rates given by Nugis & Lamers have difficulties in explaining the
luminosity distribution of WR stars of WC and WO types and the SN Ic progenitor
properties. Here we suggest some improvements in the WR mass-loss rate
prescription and discuss its implications for the evolution of WR stars and SN
Ib/Ic progenitors. Recent studies on Galactic WR stars clearly indicate that
the mass-loss rates of WC stars are systematically higher than those of WNE
stars for a given luminosity. The luminosity and initial metallicity
dependencies of WNE mass-loss rates are also significantly different from those
of WC stars. These factors have not been adequately considered together in
previous stellar evolution models. We also find that an overall increase of WR
mass loss rates by about 60 per cent compared to the empirical values obtained
with a clumping factor of 10 is needed to explain the most faint WC/WO stars.
This moderate increase with our new WR mas-loss rate prescription results in SN
Ib/Ic progenitor models more consistent with observations than those given by
the Nugis & Lamers prescription. In particular, our new models predict that the
properties of SN Ib and SN Ic progenitors are distinctively different, rather
than they form a continuous sequence.
