Wolf-Rayet Star Death Linked to Newly Spotted Supernova with New Technique

Wolf-Rayet stars are both very large and very hot, and scientists have long wondered whether when these massive stars die, they create certain types of supernovae. Now, researchers may have the answer. They've identified a Wolf-Rayet star as the likely progenitor of a recently-exploded supernova.

Wolf-Rayet stars possess strong stellar winds and are deficient in hydrogen-at least when compared with other stars. They're easily recognizable by their stellar signatures. That's why scientists have long wondered whether these stars explode as type IIb, Ib or Ic supernovae. Unfortunately, little direct evidence has been available to link these stars to these supernovae-until now.

The scientists used the Palomar 48-inch telescope in California to spot the supernova, called SN 2013cu. Then, they employed a novel observational method called flash spectroscopy in order to identify the likely progenitor of the type IIb supernova.

Supernovae themselves are the result of a star essentially exploding at the end of its life. It can cause a massive burst of light and, in this case, flash ionized its immediate surroundings. This allowed astronomers to receive a directly glimpse of the progenitor star's chemistry.

Using flash spectroscopy, the researchers found direct evidence of composition and shape that aligns with that of nitrogen-rich Wolf-Rayet stars. The researchers had to work quickly, though; the opportunity to examine the supernova before the supernova blast swept the ionization away. Yet the findings seemed to indicate that Wolf-Rayet stars are, indeed, the progenitors of these types of supernovae. Not only that, but the scientists found that the star most likely experienced an increased loss of mass shortly before the explosion. This, in particular, is consistent with model predictions for Wolf-Rayet explosions.

The findings shed a bit of light on the evolution of massive stars. By understanding how Wolf-Rayet stars evolve, researchers can improve models and also learn a bit more about the supernovae that they encounter.

The findings were published in the journal Nature.