UC Santa Cruz

How a massive star ends its life depends upon how that life has been lived - the rotation, mass and composition it was born with, mass loss and exchange, and the complex convective and nuclear burning episodes it experienced along the way. In the end, the presupernova stellar core has a density structure that can be characterized by its "compactness" - essentially how fast the density declines outside the iron core. The likelihood that a massive star explodes, by any means, is sensitive to this compactness. It turns out, perhaps surprisingly, that the compactness is not a monotonic function of the star's birth mass, and, in some mass regions, whether the star explodes or not is almost random. Here the stellar physics underlying the development of compactness is explored for a fine grid of masses across a broad range of masses (9 - 120 solar masses). Using the model set generated, and with collaborators, the resulting explosions are explored assuming a neutrino-powered mechanism. Full isotopic nucleosynthesis, light curves, and remnant masses are calculated and found to be in good agreement with observations. Neglecting rotation, most stars above 20 Msun do not explode - though there are exceptions. In a related study, based on the same model set, the upper bound to the most luminous supernovae is explored considering various energy sources. The brightest possible supernova is found to be a rotationally powered explosion of a stripped core.