The Peculiar Type Ib Supernova 2006jc: a Wc Star Explosion

We present a theoretical model for Type Ib supernova (SN) 2006jc associated with a luminous blue variable (LBV)-like event. We calculate the presupernova evolution of the progenitor star, hydrodynamics and nucleosynthesis of the SN explosion, and the SN bolometric light curve (LC). The observed bolometric LC is constructed by integrating the UV, optical, near-infrared (NIR), and midinfrared (MIR) fluxes. The progenitor is assumed to be as massive as 40M⊙ on the zero-age. The star undergoes extensive mass loss to reduce its mass down to as small as 6.9M⊙, thus becoming a WC Wolf-Rayet star at the presupernova stage. The WC star model has a thick carbon-rich layer, in which amorphous carbon grains can be formed during the explosion. This could explain the brightening in the NIR flux and the observed dust feature in MIR. The typical main-sequence mass of a WC WolfRayet star and thus the progenitor of SN 2006jc is more massive than 40M⊙. We suggest that the explosions of stars more massive than 40M⊙ are the important source of dust formation. We derive the parameters of the explosion model in order to reproduce the bolometric LC of SN 2006jc by the radioactive decays; the best model has the ejecta mass of 4.9M⊙, the hypernova-like explosion energy of 10 ergs, and the ejected Ni mass of 0.22M⊙. We also calculate the circumstellar interaction and find that such a shallow CSM density gradient as ρ ∝ r is required to reproduce the X-ray LC of SN 2006jc. This suggests a drastic change of the mass-loss rate and/or the wind velocity that seems to be consistent with the past LBV-like event. Subject headings: dust, extinction — infrared: ISM — nuclear reactions, nucleosynthesis, abundances — supernovae: general — supernovae: individual (SN 2006jc) — stars: Wolf-Rayet