Scientists from the RIKEN Cluster for Pioneering Study have used computer modeling to exhibit how a hypothesized type of supernova would evolve on the size of thousands of years, giving scientists a way to look for examples of supernovae of this model, known as “ D 6 . ”
Supernovae are important for cosmology, as one type, Ia, can be used as a “ standard candle” that allows distance to be measured, and in fact they were used for the measurements that showed, surprisingly to initial observers, that the expansion of the world is accelerating. It is generally accepted that type Ia supernovae arise from the explosion of degenerate stars known as white dwarfs — stars which have burned through their hydrogen and shrunk into compact objects— but the mechanism that triggers the explosions is not properly understood.
Recently, the discovery of whitened dwarfs that are moving incredibly rapidly has given added credibility to one proposed system for the origin of these supernovae, D 6 . In this scenario, one of two whitened dwarfs in a binary system undergoes what is known as a “ double detonation, ” where a surface layer of helium first explodes, then igniting a larger explosion in the carbon-oxygen core of the star. This may lead to the obliteration of the superstar, and the companion, suddenly free of the gravitational attraction from the exploding star, is flung out at enormous speed.
However , hardly any is known about what shape the remnant of such an occasion would look like long after the original explosion. To explore this, the team decided to simulate the particular long-term evolution, in the form of a supernova remnant, for thousands of years after the explosion. In fact , they were able to see some features in the progenitor system that would be specific to this scenario, thus offering a way to probe supernova physics, including a “ shadow” or even dark patch surrounded by a bright ring. They also concluded that the remnants of kind Ia explosions are not always symmetric, as is commonly considered.
According to Gilles Ferrand, the first author of the study, “ The D 6 supernova explosion has a specific shape. We were not confident it would be visible in the remnant long after the initial event, yet actually we found that there is a specific signature that we can still see thousands of years after the explosion. ”
Shigehiro Nagataki, the leader of the Astrophysical Big Bang Laboratory in RIKEN, says, “ It is a very important finding, because it might have an impact on the use of Ia supernovae as cosmic yardsticks. They were once believed to originate from a single phenomenon, but if they are diverse, then it might require a reevaluation of how we use them. ”
Ferrand continues, “ Moving forward, we plan to learn how to more precisely calculate the X-ray emission, taking into account the composition and state of the shocked plasma, to make direct comparisons with observations. We hope that our paper can give new ideas to observers, associated with what to look for in supernova remnants. ”
The investigation, done in conjunction with an worldwide group including researchers in the University of Manitoba, has been published in The Astrophysical Journal .