Wolf-Rayet stars of the carbon sequence ( WC stars ) are an important cornerstone in the late evolution of massive stars before their core collapse .
As core-helium burning , hydrogen-free objects with huge mass-loss , they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae .
Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds .
Thus , the determination of the WC star parameters is of major importance for several astrophysical fields .
With Gaia DR2 , for the first time parallaxes for a large sample of Galactic WC stars are available , removing major uncertainties inherent to earlier studies .

In this work , we re-examine a previously studied sample of WC stars to derive key properties of the Galactic WC population .
All quantities depending on the distance are updated , while the underlying spectral analyzes remain untouched .
Contrasting earlier assumptions , our study yields that WC stars of the same subtype can significantly vary in absolute magnitude .

With Gaia DR2 , the picture of the Galactic WC population becomes more complex : We obtain luminosities ranging from \log L / L _ { \odot } = 4.9 up to 6.0 with one outlier ( WR 119 ) having \log L / L _ { \odot } = 4.7 .
This indicates that the WC stars are likely formed from a broader initial mass range than previously assumed .
We obtain mass-loss rates ranging between \log \dot { M } = -5.1 and -4.1 , with \dot { M } \propto L ^ { 0.68 } and a linear scaling of the modified wind momentum with luminosity .

We discuss the implications for stellar evolution , including unsolved issues regarding the need of envelope inflation to address the WR radius problem , and the open questions in regard to the connection of WR stars with Gamma-ray bursts .
WC and WO stars are progenitors of massive black holes , collapsing either silently or in a supernova that most-likely has to be preceded by a WO stage .