2014MNRAS.439.3694J

We present nebular-phase optical and near-infrared spectroscopy of the Type IIP supernova SN 2012aw combined with non-local thermodynamic equilibrium radiative transfer calculations applied to ejecta from stellar evolution/explosion models. Our spectral synthesis models generally show good agreement with the ejecta from a MZAMS = 15 M_☉ progenitor star. The emission lines of oxygen, sodium, and magnesium are all consistent with the nucleosynthesis in a progenitor in the 14-18 M_☉ range. We also demonstrate how the evolution of the oxygen cooling lines of [Oi] λ5577, [Oi] λ6300, and [Oi] λ6364 can be used to constrain the mass of oxygen in the non-molecularly cooled ashes to <1 M_☉, independent of the mixing in the ejecta. This constraint implies that any progenitor model of initial mass greater than 20 M_☉ would be difficult to reconcile with the observed line strengths. A stellar progenitor of around MZAMS = 15 M_☉ can consistently explain the directly measured luminosity of the progenitor star, the observed nebular spectra, and the inferred pre-supernova mass-loss rate. We conclude that there is still no convincing example of a Type IIP supernova showing the nucleosynthesis products expected from an MZAMS > 20 M_☉ progenitor.