Detailed Mapping of Extreme Mass-Loss with coordinated XMM-NuSTAR observations

Contrary to expectations from current stellar evolutionary models, recent observations uncovered the ejection of shells of material by massive stars in the years before the supernova (SN) explosion. The physical mechanism behind the impulsive mass ejection synchronized with the stellar core-collapse is unclear. Here we propose a coordinated NuSTAR-XMM effort to map the evolution of the broad-band X-ray spectrum of 1 nearby (d< 50 Mpc) strongly interacting SN and enable progress. Our program has the immediate goal to characterize the medium around strongly interacting SN, which originate from stellar progenitors with the most extreme mass loss before explosion.