Presentation #200.06 in the session Multi-Messenger and Time Domain Astronomy.
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 >60 type II supernovae (SNe II) whose early-time spectra showed transient, narrow emission lines from shock interaction (i.e., “flash spectroscopy”) with confined circumstellar material (CSM) around their red supergiant progenitor stars. 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. Lastly, I will present modeling of these SNe using NLTE hydrodynamical simulations, which allowed for the best constraints to date to be made on the global properties of the progenitor stars responsible for these fascinating events as well as the structure of their CSM.