Populations of WC and WN stars in WR galaxies: new constraints on   starburst parameters
  Detection and analysis of Wolf-Rayet (WR) star populations in young starbursts is a powerful tool to reveal the properties of the star-forming events. We present new high S/N optical spectra of a sample of well-known WR galaxies, in which we detected for the first time the spectral signature of WC stars. The detailed comparison of WN and WC star populations derived in these galaxies, with the most recent model predictions, allows to put tight constraints on starburst parameters, such as the age and duration of the burts, and the IMF. 
Thierry Contini (ESO, Garching), Daniel Schaerer (OMP, Toulouse),   Daniel Kunth (IAP, France)