Constraints On the Explosion Mechanisms of SNe Ia from Optical and NIR Nebular Phase Spectroscopy

Even though Type Ia supernovae (SNe Ia) are widely used in cosmology, the debate about their progenitors remains unsettled. Many viable progenitors and explosion mechanisms have been proposed so far. Nucleosynthetic yields of neutron‐rich iron group elements are the fingerprints of the explosion mechanism. Significant amounts can only be produced if the explosive burning occurs at high densities or metallicities. In the nebular phase the outer layers of the supernova have become transparent and we can observe the central region of the explosion which contains the iron‐group elements. There are many observations of SNe Ia in the optical, but near-IR data is still rare. I will discuss how NIR observations can help us constrain the excitation conditions of the iron core hundreds of days after the explosion through non-LTE modelling of iron, cobalt and nickel. I will present a statistical study of the neutron-rich material abundances from the modelling of optical spectra, NIR spectra and the combination of both. Finally, I will link the results from the statistical analysis of the nucleosynthetic yields to explosion model predictions and argue implications on the progenitor system