Astrophysics Seminar: The Progenitors of Type la Supernova Explosions are Head-on Collisions of White Dwarfs in Triple Systems

Abstract:

We argue that type Ia supernovae (SNe Ia) are the result of head-on collisions of White Dwarfs (WDs) in triple systems. The thermonuclear explosions resulting from the zero-impact-parameter collisions of WDs are calculated from first principles by using 2D hydrodynamical simulations. Collisions of typical WDs with masses 0.5-0.9 Msun result in explosions that synthesize 56Ni masses in the range of 0.15-0.8M Msun, spanning the wide distribution of yields observed for the majority of SNe Ia. The robustness of the shock ignition process is
verified with a detailed study using a one-dimensional toy model and analytic tools. The late-time (& 50 days after peak) bolometric light curve is equal to the instantaneous energy deposition and is calculated exactly, by solving the transport of gmma-rays emitted by the decay of 56Ni using a Monte-Carlo code. All collisions are found to have the same late-time light curves, when normalized to the amount of synthesized 56Ni. This universal light curve is shown to agree with the majority of the supernovae in the compilation made by M. Stritzinger to an accuracy of better than 30% in the range 40 < t < 80 days after bolometric peak. The widths of the 56Ni mass- weighted-line-of-sight velocity distributions are correlated with the
56Ni yield and in agreement with the observed Mazzali relation. The continuous distribution of observed SN Ia features, is naturally reproduced with the distribution of WD masses involved in the collisions.

Seminar Organiser: Prof. Rennan Barkana