Nucleosynthesis Constraints on the Explosion Mechanism for Type Ia Supernovae

Abstract

Observations of type Ia supernovae include information about the characteristic nucleosynthesis associated with these thermonuclear explosions. We consider observational constraints from iron-group elemental and isotopic ratios, to compare with various models obtained with the most-realistic recent treatment of electron captures. The nucleosynthesis is sensitive to the highest white-dwarf central densities. Hence, nucleosynthesis yields can distinguish high-density Chandrasekhar-mass models from lower-density burning models such as white-dwarf mergers. We discuss new results of post-processing nucleosynthesis for two spherical models (deflagration and/or delayed detonation models) based upon new electron capture rates. We also consider cylindrical and 3D explosion models (including deflagration, delayed-detonation, or a violent merger model). Although there are uncertainties in the observational constraints, we identify some trends in observations and the models. We make a new comparison of the models with elemental and isotopic ratios from five observed supernovae and three supernova remnants. We find that the models and data tend to fall into two groups. In one group low-density cores such as in a 3D merger model are slightly more consistent with the nucleosynthesis data, while the other group is slightly better identified with higher-density cores such as in single-degenerate 1D-3D deflagration models. Hence, we postulate that both types of environments appear to contribute nearly equally to observed SNIa. We also note that observational constraints on the yields of 54 Cr and 54 Fe, if available, might be used as a means to clarify the degree of geometrical symmetry of SNIa explosions. kanji.mori@nao.ac.jp arXiv:1808.03222v2 [astro-ph.HE] 22 Aug 2018 2 Mori et al.

Discovery of a Highly Neutronized Ejecta Clump in the Type Ia Supernova Remnant 3C 397

“…At lower densities around 1 × 10 9 g cm −3 , the neutronized nucleosynthesis products are dominated by 58 Ni, since the neutron excess in the NSE is not high enough to produce stable Ti and Cr. For this reason, the mass ratios of Ti/Ni and Cr/Ni at the innermost part offer the most sensitive indicators of the central density of near-M Ch WDs (e.g., Mori et al 2018).…”

44Ti ejecta in young supernova remnants

“…Observations of late optical spectra allow for the determination of mass ratios of synthesized elements, constraining the burning mechanisms (Eriksen et al 2009;Pakmor et al 2010;Jerkstrand et al 2015;Maguire et al 2018;Mori et al 2018). However, the total ejected mass remains a free parameter.…”

The similarity of the interstellar comet 2I/Borisov to Solar System comets from high-resolution optical spectroscopy

“…Indeed, the relative abundances of metals produced by type 1a supernovae nucleosynthesis varies depending on the explosion mechanism or the initial conditions of the white dwarf (Leung & Nomoto 2018;Palla 2021). The material produced by those supernovae then feeds the interstellar medium and can be integrated in forming planetary systems, leaving an imprint on the composition of comets that could be measurable given the large variations of the Ni/Fe ratios observed in supernovae (Mori et al 2018).…”