Light Curves of Type I Supernovae

Abstract

The light curve of Type I supernovae (SNe I), i.e. the explosion of H-deficient stars, is mainly powered by radioactive decay. Despite their different physical origin, thermonuclear explosions of white dwarfs (SNe Ia) and core-collapse explosions of massive stars with H-free envelopes (SNe Ib/c) can be understood in the same framework. The overall morphology of the light curves is similar for all SNe I. The small radius of the progenitor is responsible for the rapid degrading of the shock energy, leading to a fast initial peak that is usually unobserved. Thereafter, the luminosity of the SN and the shape of its light curve are determined by the radioactive energy input (56Ni and 56Co are the primary radioactive isotopes that power the light curve) and by the mass of the ejecta and the energy of the explosion. The energy of the explosion sets the expansion velocity which then critically determines the density and opacity of the gas. Physical parameters of the progenitor star and the explosion itself can be estimated from the shape of the light curve or derived more accurately by modeling the evolution of the light curve and the spectra simultaneously.