Abstract:
We present optical photometry and spectroscopy of the Type IIP supernova SN 2004et that occurred in the nearby galaxy NGC 6946. The observations span a time range of 8–541 d after explosion. The late time bolometric luminosity and the Hα luminosity in the nebular phase indicate that 0.06 ± 0.02 Mo of 56Ni was synthesized during the explosion. The plateau luminosity, its duration and the expansion velocity of the supernova at the middle of the plateau indicate an explosion energy of Eexp = 1.20+0.38-0.30 × 1051 erg. The late time light curve and the evolution of the [O i] and Hα emission-line profiles indicate the possibility of an early dust formation in the supernova ejecta. The luminosity of [O i] 6300, 6364 Å doublet, before the dust formation phase, is found to be comparable to that of SN 1987A at similar epochs, implying an oxygen mass in the range 1.5–2 Mo, and a main-sequence mass of 20 Mo for the progenitor.
