Picture of the Death of the Most Massive Stars
Institute of Astronomy Andalusia | 2019 Jan 16
A work studies in detail the death of a massive star that produced a gamma-ray burst (GRB) and a hypernova
This analysis confirms the existence of a jet emerging from the nucleus of the star, producing the GRB, and adds a new component to the picture
During the early phases, the jet interacts with the external layers of the star, forming a cocoon, into which it deposits part of its energy, and which could give clues as to why some hypernovae do not have an associated GRB
The end of a star's life can occur in a tranquil manner in the case of low mass stars, such as the Sun. This is not the case, however, for very massive stars, which suffer such extreme explosive events that they can outshine the brightness of the whole galaxy that hosts them. An international group of astronomers has published a detailed study of the death of a high-mass star that produced a gamma-ray burst (GRB) and a hypernova, in which they have detected a new component in this type of events. The study, published in Nature, provides a link that completes the scenario that relates hypernovae with GRBs. ...
The scenario that has been proposed to explain the phenomena involves a star over 25 times more massive than the Sun that, once it has exhausted its fuel, suffers the collapse of its core. During this collapse, the nucleus of the star transforms either into a neutron star or a black hole, and at the same time, two polar jets of matter are ejected. These jets drill through the external layers of the star and, once out of the star, produce detectable gamma-rays (the so-called GRB). Finally, the external layers of the star are ejected, generating a hypernova explosion, tens of times brighter than a typical supernova.
Although the connection between GRBs and hypernovae has been well established over the last 20 years, the opposite is not so clear, since there have been several hypernovae that do not have associated GRBs. ... On the other hand, the jet can fail to pierce the external layers of the star and never emerge into the circumstellar medium if it lacks the necessary energy. In this case we would observe a hypernova but not a GRB. The cocoon detected in this study is the link between the two subtypes of hypernovae that had been studied until now, and the chocked jets would naturally explain the observed differences. ...
Jet Cocoon Signatures in the Early Spectra of a γ-ray Burst/Supernova ~ L. Izzo et al
- Nature 565(7739):324 (17 Jan 2019) DOI: 10.1038/s41586-018-0826-3