086342

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