Winds from stripped low-mass Helium stars and Wolf-Rayet stars
  We present mass-loss predictions from Monte Carlo radiative transfer models
for helium (He) stars as a function of stellar mass, down to 2 Msun. Our study
includes both massive Wolf-Rayet (WR) stars and low-mass He stars that have
lost their envelope through interaction with a companion. For these low-mass
He-stars we predict mass-loss rates that are an order of magnitude smaller than
by extrapolation of empirical WR mass-loss rates. Our lower mass-loss rates
make it harder for these elusive stripped stars to be discovered via line
emission, and we should attempt to find them through alternative methods
instead. Moreover, lower mass-loss rates will make it less likely that low-mass
He stars provide stripped-envelope supernovae (SNe) of type Ibc. We express our
mass-loss predictions as a function of L and Z, and not as a function of the He
abundance, as we do not consider this physically astute given our earlier work.
The exponent of the dM/dt vs. Z dependence is found to be 0.61, which is less
steep than relationships derived from recent empirical atmospheric modelling.
Our shallower exponent will make it more challenging to produce "heavy" black
holes of order 40 Msun, as recently discovered in the gravitational wave event
GW 150914, making low metallicity for these types of events even more
necessary.
