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Emmanouil "Manos" Chatzopoulos and J. Craig Wheeler (University of Texas at Austin) have just published, in the Astrophysical Journal, the results of an analysis of supernova 2008am, one of the brightest ever observed, and belonging to the class of Super-Luminous Supernovae (SLSNe).
This extremely rare class contains only about a dozen examples, five of which were discovered by the ROTSE Supernova Verification Project (which uses the 18-inch robotic ROTSE IIIb telescope at McDonald Observatory), including the first two ever seen, SN 2005ap and SN 2006gy.
Apart from being up to 100 times more luminous than the classical core-collapse SN, the SLSNe can also have much more massive progenitors, sometimes over 100 solar masses (compared to 10-20 solar masses for normal core-collapse SN). Despite the small number of examples, it would appear that their progenitor stars aren't always of the same type; their extreme luminosity is all they have in common.
In the specific case of SN 2008am, Chatzopoulos and Wheeler hypothesise that the progenitor could be a massive luminous blue variable, a type of star that periodically throws off shells of gas, just as done by Eta Carinae. When, at the end of its life, the star explodes, the ejected material impacts the gas in these surrounding shells (that travel outwards much more slowly). The resulting impact is so energetic that the luminosity generated is equivalent to 100 billion Suns.
iven the enormous distance to this SN, 3.7 billion light years, it has been necessary to use some of the largest ground-based telescopes to study the object, such as Keck (that took the image above) as well as the Swift satellite.
The results obtained by Chatzopoulos and Wheeler seem to explain the origin of half of the known SLSNe, but of course the question now is, "How do we explain the other half?". The only certainty is that the traditional model used to explain core-collapse supernovae does not seem to be applicable to SLSNe, so that other physical mechanisms must be brought into play.
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