Models for the Late-time Excess Flux of the Peculiar Iax SN 2012Z

SN 2012Z was a type Iax supernova, the largest class of peculiar white-dwarf supernovae, and is the only white-dwarf supernova that has been detected in pre-explosion observations. We will present Hubble Space Telescope observations of SN 2012Z taken four years after explosion. Surprisingly, the SN has remained brighter than the pre-explosion measurements at these late epochs. We will present a variety of physical mechanisms that could explain these measurements including radioactive decay of long lived isotopes, circumstellar interaction, shock heating of a companion star, and winds from a surviving bound remnant. We will also present simple models of the energetics of type Iax supernovae which favor a Chandrasekhar mass progenitor.