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Wolf-Rayet stars of the carbon sequence (WC stars) are an importantcornerstone in the late evolution of massive stars before their core collapse.As core-helium burning, hydrogen-free objects with huge mass-loss, they arelikely the last observable stage before collapse and thus promising progenitorcandidates for type Ib/c supernovae. Their strong mass-loss furthermoreprovides challenges and constraints to the theory of radiatively driven winds.Thus, the determination of the WC star parameters is of major importance forseveral astrophysical fields. With Gaia DR2, for the first time parallaxes fora large sample of Galactic WC stars are available, removing major uncertaintiesinherent to earlier studies. In this work, we re-examine the sample from Sanderet al. (2012) to derive key properties of the Galactic WC population. Allquantities depending on the distance are updated, while the underlying spectralanalyses remain untouched. Contrasting earlier assumptions, our study yieldsthat 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 = 4.9 to 6.0 with one outlier havinglog L = 4.7. This indicates that the WC stars are likely formed from a broaderinitial mass range than previously assumed. We obtain mass-loss rates rangingbetween log Mdot = -5.1 and -4.1, with Mdot propto L^0.68 and a linear scalingof the modified wind momentum with luminosity. We discuss the implications forstellar evolution, including unsolved issues regarding the need of envelopeinflation to address the WR radius problem, and the open questions in regard tothe connection of WR stars with Gamma-ray bursts. WC and WO stars areprogenitors of massive black holes, collapsing either silently or in asupernova that most-likely has to be preceded by a WO stage.

The Galactic WC and WO stars: The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors