2009ApJ...704.1251C

We consider simple models based on core collapse or pair-formation supernovae (SNe) to account for the light curve of the transient SCP06F6. A radioactive decay diffusion model provides estimates of the mass of the required radioactive nickel and the ejecta as functions of the unknown redshift. An opacity change such as by dust formation or a recombination front may account for the rapid decline from maximum. Within this class of model, the redshift must be less than z ∼ 1 or the nickel mass would exceed the total mass of the ejecta; the radiated energy would exceed the kinetic energy, and kinematic and photometric estimates of the radius would disagree. We particularly investigate two specific redshifts: z = 0.143, for which Gaensicke et al. have proposed that the unidentified broad absorption features in the spectrum of SCP06F6 are C₂ Swan bands, and z = 0.57 based on a crude agreement with the Ca H&K and UV iron-peak absorption features that are characteristic of SNe of various types. For the lower redshift, we obtain a nickel mass of 0.3 M_☉ and an ejected envelope mass of ∼ 38 M_☉, while for the latter case we find 4.8 M _☉ and 20 M_☉, respectively, for fiducial parameters. The kinetic energy of the ejecta, while dependent on uncertain parameters, is generally large, ∼10⁵² erg, throughout this range of redshift. The ejected masses and kinetic energies are smaller for a more tightly constrained model invoking envelope recombination. We also discuss the possibilities of circumstellar matter (CSM) shell diffusion and shock interaction models. In general, optically thick CSM diffusion models can fit the data with the underlying energy coming from an energetic buried SN. Models in which the CSM is of lower density so that the shock energy is both rapidly thermalized and radiated tend not to be self-consistent. We suggest that a model of SCP06F6 worth further exploration is one in which the redshift is ∼0.57, the spectral features are Ca and iron-peak elements, and the light curve is powered by the diffusive release of a substantial amount of energy from nickel decay or from an energetic SN buried in the ejecta of an LBV-like event.