Wynn Jacobson-Galán, UC Berkeley
Final Moments: Observational Properties and Physical Modeling of Flash Spectroscopy Supernovae
There is now an amalgam of observational evidence that massive stars undergo enhanced and/or eruptive mass-loss in their final years before explosion. In this talk, I will present multi-wavelength observations of >40 type II SNe whose very early-time (“flash”) spectra showed transient, narrow emission lines from shock interaction with confined circumstellar material (CSM) around their RSG progenitor stars prior to shock breakout. I will discuss the observational properties of this “flash spectroscopy” SN sample, the largest to date, and how these objects compare to normal SNe II that arise from stars without significant mass-loss. This sample also includes the CSM-interacting type II SN 2023ixf, the closest and brightest SN of the decade, which was discovered within an hour of explosion. Lastly, I will present modeling of these SNe using non-LTE radiative transfer code CMFGEN, which allowed for the best constraints to date to be made on the CSM structure and mass-loss histories of the RSG progenitors responsible for these fascinating events.