S20A0032abst
S20A0032
We propose GMOS-S rapid ToO spectroscopy starting within 24 hrs after the discovery, for 3 nearby very young supernovae (SNe) within 50 Mpc. Such rapid spectroscopic data within a few days after the explosion is key to diagnosing the circumstellar (CS) environment around a progenitor star, which can be translated to the still-unclarified mass loss history of a massive star in the final years before the explosion. While such quick optical spectroscopy has opened a new time-domain window and brought many surprises in the last few years, a synergetic follow-up program coordinated with radio observation, which is the most powerful probe to the CS environment, is still missing. For S20A, the proposal team has secured observing time to observe a nearby SN soon after the discovery in sub-mm wavelengths by ALMA, and a few SNe in cm wavelengths by ATCA and GMRT. Combined with the proposed Gemini observation, it will provide the first opportunity to clarify the final evolution of massive stars in the last few years from a synoptic view point, by robustly determining the nature of the CS environment in the vicinity of SN progenitor star.
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