The Wolf-Rayet Stars are massive stars (>25 solar masses) in an advanced stage of evolution and ejecting at high velocity a hot gas (100km/sec typical). The spectrum presents strong emission lines. Wolf-Rayet stars have lost their atmospheres and have exposed their massive cores. One finds the signiture of ions of helium, carbon, nitrogen and oxygen in their spectra.

There are two flavors of W-R stars, type WN where nitrogen and helium ions dominate and type WC where carbon and oxygen in multiple states of ionization are observed.

These stars are very rare. One counts only around 150 in our galaxy. They are often associated wioth planetary type nebula.

Example of type WC:

Example of type WN: