X-rays and Flash Spectroscopy as an Unprecedented Probe of Mass-loss

The overarching goal is to identify the unknown progenitors of both Hpoor,core collapse and CalciumRich supernovae (SNe) by mapping the masslosshistory in the final years before explosion through the novel combination ofXray emission and flash spectroscopy as a probe of the circumstellarenvironment. This coordinated observational technique is now possible with ouraccess to the Young Supernova Experiment (YSE), a new untargeted transientsurvey designed to systematically discover SNe in the first days afterexplosion. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]