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Author:
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Soderberg, A. M.; Chakraborti, S.; Pignata, Giuliano; Chevalier, R. A.; Chandra, P.; Ray, Aurkie; Wieringa, M. H.; Copete, A.; Chaplin, V.; Connaughton, V.; Barthelmy, S. D.; Bietenholz, M. F.; Chugai, N.; Stritzinger, M. D.; Hamuy, Mario; Fransson, C.; Fox, O.; Levesque, Emily M.; Grindlay, J. E.; Challis, P.; Foley, Ryan J.; Kirshner, Robert P.; Milne, P. A.; Torres, M. A. P.
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Abstract:
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Long duration c-ray bursts (GRBs) mark1 the explosive death of some
massive stars and are a rare sub-class of type Ibc supernovae. They are
distinguished by the production of an energetic and collimated relativistic
outflow powered2 by a central engine (an accreting black hole or
neutronstar).Observationally, thisoutflow ismanifested3 in thepulse
of c-rays and a long-lived radio afterglow. Until now, central-enginedriven
supernovae have been discovered exclusively through their
c-ray emission, yet it is expected4 that a larger population goes undetected
because of limited satellite sensitivity or beaming of the collimated
emission away from our line of sight. In this framework, the
recovery ofundetectedGRBsmaybepossible throughradio searches5,6
for type Ibc supernovae with relativistic outflows. Here we report the
discovery of luminous radio emission from the seemingly ordinary
type Ibc SN 2009bb, which requires a substantial relativistic outflow
powered by a central engine. A comparison with our radio survey of
type Ibc supernovae reveals that the fraction harbouring central
engines is low, about one per cent, measured independently from,
but consistent with, the inferred7 rate of nearby GRBs. Independently,
a secondmildly relativistic supernova has been reported8. |