Wolf–Rayet 星(富含氢的外层被剥离的巨大天体)是IIb、Ib 和Ic型爆炸的超新星前身星的若干候选对象之一。这篇论文报告，在来自IIb型超新星SN 2013cu的早期光谱(仅在爆炸之后15小时)中检测到了强发射线，这与Wolf–Rayet 星是前身星的判断相一致。这种致密的超新星风( supernova wind)的程度意味着，在爆炸之前不久该前身星的物质损失可能会增加，这与最近的理论预测相一致。为该论文配发的一篇News & Views文章提出，这些新发现是迄今获得的最直接证据，证明这些巨大恒星的确以超新星的形式来结束它们的生命。
The explosive fate of massive Wolf–Rayet stars1 (WRSs) is a key open question in stellar physics. An appealing option is that hydrogen-deficient WRSs are the progenitors of some hydrogen-poor supernova explosions of types IIb, Ib and Ic (ref. 2). A blue object, having luminosity and colours consistent with those of some WRSs, has recently been identified in pre-explosion images at the location of a supernova of type Ib (ref. 3), but has not yet been conclusively determined to have been the progenitor. Similar work has so far only resulted in non-detections. Comparison of early photometric observations of type Ic supernovae with theoretical models suggests that the progenitor stars had radii of less than 1012 centimetres, as expected for some WRSs5. The signature of WRSs, their emission line spectra, cannot be probed by such studies. Here we report the detection of strong emission lines in a spectrum of type IIb supernova 2013cu (iPTF13ast) obtained approximately 15.5 hours after explosion (by ‘flash spectroscopy’, which captures the effects of the supernova explosion shock breakout flash on material surrounding the progenitor star). We identify Wolf–Rayet-like wind signatures, suggesting a progenitor of the WN(h) subclass (those WRSs with winds dominated by helium and nitrogen, with traces of hydrogen). The extent of this dense wind may indicate increased mass loss from the progenitor shortly before its explosion, consistent with recent theoretical predictions.