(ORDO NEWS) — An international team of astronomers led by Benjamin Thomas of the University of Texas at Austin, USA, used observations made with the McDonald Observatory’s Hobby-Eberly Telescope (HET) to figure out the nature of an unusual stellar explosion discovered several years ago and actively evolving since that time.
Thomas and his team have been observing this supernova, dubbed SN 2014C, since it was first discovered in 2014. In the binary system that gave rise to this supernova, the more massive star evolved faster, began to expand, and lost its outer hydrogen shell, captured by the gravity of the second star.
In the inner core of the first star, thermonuclear fusion continued until all the reserves of “stellar fuel” were exhausted. When this happened, the external pressure from the core decreased and the core collapsed, giving rise to a class Ib supernova.
However, observations of this supernova by Thomas and his team revealed a number of unusual properties. First, optical observations of supernova SN 2014C revealed signs of hydrogen, which is highly unusual for a typical class Ib supernova.
Second, the optical brightness of this hydrogen did not follow the usual pattern of increasing brightness, reaching a maximum, and then fading. Instead, the brightness remained constant.
According to the hypothesis proposed by the authors, the problem with explaining the properties of this source was that the model used assumed a spherically symmetric supernova explosion and shock wave propagation. However, data obtained with the HET telescope disproved this possibility.
The team then proposed a model in which the hydrogen shells of individual stars in the binary system that gave rise to this supernova combined to form a common shell.
Then there was a separation of the shell from this pair and the formation of a disk-shaped structure expanding into space surrounding both stars. When one of the stars then exploded, its fast-moving material collided with the slow-moving disk and began to skim across the disk’s surface.
The team showed that the interface between the disk and the material sliding on it is precisely where the hydrogen found during observations of this source is concentrated. Thus, with the help of the HET telescope, the long-standing secret of this unusual supernova was revealed for the first time, the authors noted.
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