Astronomy Colloquium

Supernovae (SNe) play a critical role in modern astrophysics. Their extraordinary luminosity makes them prime beacons of the distant Universe and thus critical tools for cosmology. These catastrophic stellar death and explosion are a major contribution to the chemical enrichment of the Universe, from the first generation of stars to now. SNe come in different flavors, in association with white-dwarf thermonuclear explosions in the single- and double-degenerate scenarios (Type Ia), with the gravitational collapse of massive stars (Type II/Ib/Ic), with the interaction of ejected shells (Type IIn), or through the so-called pair-production instability. In this talk, I will summarize the fundamental properties of these various mechanisms and the stellar progenitors. I will then introduce a new approach to the radiative-transfer modeling of SN spectra and light curves which takes into account line blanketing and departures from Local Thermodynamic Equilibrium, as well as treats time dependent terms in the radiative-transfer, energy, and statistical-equilibrium equations. Combined with hydrodynamical inputs of SN ejecta produced from the explosion of white-dwarf, red-supergiant, blue-supergiant, or Wolf-Rayet stars, we simulate the photometric and spectroscopic evolution from early time until the nebular phase. I will describe the assets of this method, in particular the possibility of constraining the properties of the explosion and the progenitor from the combined analysis of spectra and light curves. I will also review the key radiative-transfer properties of SN ejecta. I will then illustrate with results from an on-going study of SNe IIb/Ib/Ic, of relevance to massive-star evolution and long-duration Gamma-ray bursts.