Progression from Wolf–Rayet star to type IIb supernova

Wolf–Rayet stars, massive objects stripped of their outer hydrogen-rich envelope, are one of a number of candidates as supernova progenitors for type IIb, Ib and Ic explosions. This paper reports the detection of strong emission lines in early spectra — just 15 hours after the blast — from the type IIb supernova SN 2013cu that are consistent with a Wolf–Rayet star as progenitor. The extent of this dense supernova wind implies possible increased mass loss from the progenitor shortly before the explosion, consistent with recent theoretical predictions. An accompanying News & Views article suggests that the new findings are the most direct evidence yet that these massive stars do end their lives as supernovae.