Pulsational Pair-instability Model for Superluminous Supernova PTF12dam: Interaction and Radioactive Decay

Being a superluminous supernova, PTF12dam can be explained by a ⁵⁶Ni-powered model, a magnetar-powered model, or an interaction model. We propose that PTF12dam is a pulsational pair-instability supernova, where the outer envelope of a progenitor is ejected during the pulsations. Thus, it is powered by a double energy source: radioactive decay of ⁵⁶Ni and a radiative shock in a dense circumstellar medium. To describe multicolor light curves and spectra, we use radiation-hydrodynamics calculations of the STELLA code. We found that light curves are well described in the model with 40 M_o ejecta and 20-40 M_o circumstellar medium. The ejected ⁵⁶Ni mass is about 6 M_o, which results from explosive nucleosynthesis with large explosion energy (2-3) × 10⁵² erg. In comparison with alternative scenarios of pair-instability supernova and magnetar-powered supernova, in the interaction model, all the observed main photometric characteristics are well reproduced: multicolor light curves, color temperatures, and photospheric velocities.