Driving classical Wolf-Rayet winds: A {\Gamma}- and Z-dependent
  mass-loss
  Classical Wolf-Rayet (WR) stars are at a crucial evolutionary stage for
constraining the fates of massive stars. The feedback of these hot,
hydrogen-depleted stars dominates their surrounding by tremendous injections of
ionizing radiation and kinetic energy. The strength of a WR wind decides the
eventual mass of its remnant, likely a massive black hole. However, despite
their major influence and importance for gravitational wave detection
statistics, WR winds are particularly poorly understood. In this paper, we
introduce the first set of hydrodynamically consistent stellar atmosphere
models for classical WR stars of both the carbon (C) and nitrogen (N) sequence,
i.e. WC and WN stars, as a function of stellar luminosity-to-mass ratio (or
Eddington Gamma), and metallicity. We demonstrate the inapplicability of the
CAK wind theory for classical WR stars and confirm earlier findings that their
winds are launched at the (hot) iron (Fe) opacity peak. For $\log Z/Z_\odot >
-2$, Fe is also the main accelerator throughout the wind. Contrasting previous
claims of a sharp lower mass-loss limit for WR stars, we obtain a smooth
transition to optically thin winds. Furthermore, we find a strong dependence of
the mass-loss rates on Eddington-$\Gamma$, both at solar and sub-solar
metallicity. Increases in WC carbon and oxygen abundances turn out to slightly
reduce the predicted mass-loss rates. Calculations at subsolar metallicities
indicate that below the metallicity of the SMC, WR mass-loss rates decrease
much faster than previously assumed, potentially allowing for high black hole
masses even in the local universe.
