S22A0027

We propose late-time spectroscopy of ∼ 10 type Ia supernovae (SNe Ia) by FOCAS, aiming at connecting the properties of the outermost layer and the core of exploding white dwarfs (WDs). In the first semester of 2021, there has been a rapid increase of a sample of SNe Ia with the earliest spectra obtained within a few days of explosion that allow us to study the properties of the outermost layer. We propose to study the nature of the core for these SNe by this program. It will provide a first sample of SNe Ia for which the entire ejecta structure is disclosed. We will analyze the sample with theoretical predictions; the outermost properties are sensitive to the strength of detonation and the WD mass, while the core properties are sensitive to the nature of triggering deflagration and the WD central density. By applying these diagnostics, we aim at clarifying whether SNe Ia originate in multiple populations, and how different populations are associated with different progenitor/explosion scenarios.

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