Understanding The Violent Collisions That Power Supernovae

Scientists have simulated the violent collisions between superluminous supernovae and its surrounding gas, which then emit extreme brightness.

AsianScientist (Dec. 9, 2016) – Researchers in Japan have simulated the violent collisions between supernovae and its surrounding gas to better understand its origins. Their results have been published in The Astrophysical Journal.

Many extremely bright supernovae have been discovered in the last decade, with peak luminosity of one to two orders of magnitude higher than for normal supernovae of known types. These stellar explosions are called superluminous supernovae (SLSNe). Some of them have hydrogen in their spectra, while some others demonstrate a lack of hydrogen. The latter are called Type I, or hydrogen-poor, SLSNe-I. SLSNe-I challenge the theory of stellar evolution, since even normal supernovae are not yet completely understood.

Led by Dr. Elena Sorokina, guest investigator at the Kavli Institute for the Physics and Mathematics of the Universe, and principal investigator Dr. Ken’ichi Nomoto, the team developed a model that can explain a wide range of observed light curves of SLSNe-I in a scenario which requires much less energy than other proposed models.

The models demonstrating the events with the minimum energy budget involve multiple ejections of mass in pre-supernova stars. Mass loss and buildup of envelopes around massive stars are generic features of stellar evolution. Normally, those envelopes are rather diluted, and they do not change significantly the light produced in the majority of supernovae. In some cases, a large amount of mass is expelled just a few years before the final explosion. Then, the ‘clouds’ around supernovae may be quite dense.

The shockwaves produced in collisions of supernova ejecta and those dense clouds may provide the required power of light to make the supernova much brighter than a ‘naked’ supernova without pre-ejected surrounding material. This class of the models is referred to as ‘interacting’ supernovae.

The authors show that the interacting scenario is able to explain both fast and slowly fading SLSNe-I, so the large range of these intriguingly bright objects can in reality be almost ordinary supernovae placed into extraordinary surroundings.

The article can be found at: Sorokina et al. (2016) Type I Superluminous Supernovae as Explosions inside Non-Hydrogen Circumstellar Envelopes.


Source: University of Tokyo; Photo: Pixabay.
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