Astronomers have watched the death of a star like never before, and it suggests there might be a new way for them to die.
Last year, a space telescope called the Einstein Probe spotted a quick flash of X-rays coming from a galaxy about 500 million light years away. The flash was named EP260321a and immediately the scientific world scrambled to watch its source.
In doing so, two teams of scientists both separately identified the first burst of X-rays as a “shock breakout”, which happens when the shock wave from an exploding star bursts out of its surface and sends out the first light of a supernova. Those shock breakouts are thought to happen whenever a supernova explodes – but they are hard to see because they can last just seconds, and scientists have only ever confirmed one of them before.
As they looked at it in more detail, the researchers found that the explosion was a known kind of supernova. But it was unusual: the shock breakout is the faintest ever seen with this kind of supernova, even though the explosion was not weak, and it did not emit a gamma-ray burst like other examples that have been seen.
“SN 2026gzf [the supernova involved] looks remarkably similar to other energetic supernovae that have been previously linked to gamma-ray bursts. Yet multi-wavelength follow-up observations using the most sensitive facilities found no evidence for a relativistic jet or an afterglow, which are typically seen in those events,” said Brendan O’Connor, astronomer and McWilliams Fellow at Carnegie Mellon University, who led one of the teams. “One possibility is that the jet was ‘choked,’ either by the surface of the star or by circumstellar material surrounding the star.”
To better understand the event, researchers pulled together from t4elescopes across the world. That led them watch it evolve over time and confirm that it was an Ic-BL supernova, the kind they thought.
“Our observations allowed us to study the physics of three pieces of this explosion: the X-ray shock breakout, the accompanying supernova, and the interaction of the supernova with material previously cast out by the dying star,” said Jillian Rastinejad, a Nasa Einstein Fellow at the University of Maryland, who led the other team. “With this information we were able to map out the structure of the material surrounding the star and understand the star’s violent lifestyle before it collapsed.”
That better understanding allowed the researchers to understand both the life and the death of the star in unparalleled detail. And its unusual nature suggests that stars can die in ways that were not previously understood.
The work is reported in a new paper, ‘A Multi-Wavelength View of the First Type Ic-BL Supernova with an Einstein Probe X-ray Shock Breakout’, published in The Astrophysical Journal Letters.