There have been emerging diversities seen in SNe Ia and their variants, which probably reflect differences in the progenitor evolution and explosion mechanism. We propose late-time (∼ 200 days) FOCAS spectroscopy of ∼ 10 type Ia supernovae (SNe Ia) covering various subclasses, aiming at exploring the origins of the diversities seen for exploding white dwarfs (WDs). Thanks to new generation surveys, there has been a rapid increase of a sample of SNe Ia of various subclasses observed intensively in the early phase (∼ a week to a few months after the explosion) that allow us to study the properties of the outer layer. We propose to study the nature of the core by this program, which enables us to associate the physical mechanisms to the observational diversities. By applying various new 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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