2009MNRAS.400..531S

Energy release from radioactive decays contributes significantly to supernova light curves. Previous works, which considered the energy deposited by γ-rays and positrons produced by ⁵⁶Ni, ⁵⁶Co, ⁵⁷Ni, ⁵⁷Co, ⁴⁴Ti and ⁴⁴Sc, have been quite successful in explaining the light curves of both core collapse and thermonuclear supernovae. We point out that Auger and internal conversion electrons, together with the associated X-ray cascade, constitute an additional heat source. When a supernova is transparent to γ-rays, these electrons can contribute significantly to light curves for reasonable nucleosynthetic yields. In particular, the electrons emitted in the decay of ⁵⁷Co, which are largely due to internal conversion from a fortuitously low-lying 3/2^– state in the daughter ⁵⁷Fe, constitute an additional significant energy-deposition channel. We show that when the heating by these electrons is accounted for, a slow-down in the light curve of SN 1998bw is naturally obtained for typical hypernova nucleosynthetic yields. Additionally, we show that for generic Type Ia supernova yields, the Auger electrons emitted in the ground-state to ground-state electron capture decay of ⁵⁵Fe exceed the energy released by the ⁴⁴Ti decay chain for many years after the explosion.