S19B0055abst

S19B0055

We propose late-time spectroscopy of ∼ 10 nearby supernovae (SNe) in two observing nights (separated by ∼ 2 months), aiming at constructing a golden sample of SNe that are observed from the very beginning (in the first few days, by Seimei telescope) to the late phases (150 - 300 days, by Subaru/FOCAS). The earliest-phase data are sensitive to the properties of the outermost ejecta and the closest CSM, while the late-phase data provide totally different diagnostics on the nature of the progenitor, explosion physics and the CSM in a larger scale. Given that two new facilities (Seimei and Tomo-e) have just started operation, it is time to connect these different diagnosing observations and seek for a unified picture of these stellar explosions. Our main scientific goals include a relation between the SN Ia progenitor and explosion mode, and an origin of the massive star activity in the final decades.

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