Determining the nucleosynthesis of supernovae by nebular spectral modelling
Supernovae produce elements across the periodic table and are probes of stellar evolution, explosion physics and compact object formation.
When supernovae enter the nebular phase after a few months, they reveal their interior regions where freshly made nucleosynthesis products glow from radioactivity. Each element displays characteristic emission lines and decoding these spectra offers a unique way to directly determine the products of stellar nucleosynthesis. I review the methodology to calculate model spectra of supernovae in the nebular phase, and how such models are used to determine nucleosynthesis yields from observed spectra as well as to test explosion simulations. I focus on three particular applications. The first is the production of oxygen and how O lines can be used to estimate the progenitor mass of the supernova.The second is the production of stable nickel (58Ni and 60Ni) and what the ratio of nickel to iron in a supernova tells us about the explosion physics. The third is the recent identification of never-before-seen lines of neutral iron in the superluminous supernova SN 2006gy - and how this discovery points to an unexpected origin of the brightest interacting supernovae.