The progenitor mass of the Type IIP supernova SN 2004et from late-time spectral modeling

SN 2004et is one of the nearest and best-observed Type IIP supernovae, with a progenitor detection as well as good photometric and spectroscopic observational coverage well into the nebular phase. Based on nucleosynthesis from stellar evolution/explosion models we apply spectral modeling to analyze its 140−700 day evolution from ultraviolet to mid-infrared. We find a MZAMS = 15 M⊙ progenitor star (with an oxygen mass of 0.8 M⊙) to satisfactorily reproduce [O i] λλ6300, 6364 and other emission lines of carbon, sodium, magnesium, and silicon, while 12 M⊙ and 19 M⊙ models under- and overproduce most of these lines, respectively. This result is in fair agreement with the mass derived from the progenitor detection, but in disagreement with hydrodynamical modeling of the early-time light curve. From modeling of the mid-infrared iron-group emission lines, we determine the density of the “Ni-bubble” to ρ(t) ≃ 7 × 10-14 × (t/100 d)-3 g cm-3, corresponding to a filling factor of f = 0.15 in the metal core region (V = 1800 km s-1). We also confirm that silicate dust, CO, and SiO emission are all present in the spectra.