Strange, Explosive Supernova is the Missing Link in Gamma-Ray Burst Connection

A strange supernova is actually the missing link between supernova explosions that generate gamma-ray bursts (GRBs) and those that don't. The new findings reveal a bit more about these explosive stars.

"This is a striking result that provides a key insight about the mechanism underlying these explosions," said Sayan Chakraborti, one of the researchers, in a news release. "This object fills in a gap between GRBs and other supernovae of this type, showing us that wide range of activity is possible in such blasts."

The researchers spotted the supernova for the first time in 2012. Called Supernova 2012ap (SN 2012ap), the supernova is what is known as a core-collapse supernova. This type of blast occurs when the nuclear fusion reactions at the core of a very massive star no longer can provide the energy needed to hold up the core against the weight of the outer parts of the star. The core then collapses in a superdense neutron star or a black hole, while the rest of the star's material is blasted into space.

The most common type of these supernova produce no burst of gamma rays. In a very small percentage of cases, though, the infalling material is drawn into a short-lived swirling disk surrounding the new neutron star or black hole. This disk generates jets of material that move outward from the disk's poles, and produce gamma-ray bursts.

In this case, though, the researchers have found that not all "engine-driven" supernova explosions produce gamma-ray bursts.

What we see is that there is a wide diversity in the engines in this type of supernova explosion," said Chakraborti in a news release. "Those with strong engines and lighter particles produce gamma-ray bursts, and those with weaker engines and heavier particles don't."

The findings reveal that the nature of the engine plays a central role in determine what type of supernova explosion will occur. This, in turn, reveals why some supernovae produce gamma-ray bursts and others don't.

The findings are published in The Astrophysical Journal.

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