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A progenitor for the extremely luminous Type Ic supernova 2007bi




SN 2007bi is an extremely luminous Type Ic supernova. This supernova is thought to be evolved from a very massive star, and two possibilities have been proposed for the explosion mechanism. One possibility is a pair-instability supernova with an MCO∼ 100 M CO core progenitor. Another possibility is a core-collapse supernova with MCO∼ 40 M. We investigate the evolution of very massive stars with main-sequence mass MMS= 100–500 M and Z0= 0.004, which is in the metallicity range of the host galaxy of SN 2007bi, to constrain the progenitor of SN 2007bi. The supernova type relating to the surface He abundance is also discussed. The main-sequence mass of the progenitor exploding as a pair-instability supernova could be MMS∼ 515–575 M. The minimum main-sequence mass could be 310 M when uncertainties in the mass-loss rate are considered. A star with MMS∼ 110–280 M evolves to a CO star, appropriate for the core-collapse supernova of SN 2007bi. Arguments based on the probability of pair-instability and core-collapse supernovae favour the hypothesis that SN 2007bi originated from a core-collapse supernova event.