COLLIDING WIND X-RAY EMISSION FROM THE MASSIVE BINARY WR140 AROUND PERIASTRON

The windwind collision (WWC) in eccentric massive binary systems producespredictably variable shockheated Xray plasma. This collision provides an ideallaboratory for shock astrophysics, providing key constraints on how gasthermalizes at variable density and on particle acceleration. Joint NuSTAR andXMMNewton observation of WR 140 in AO14 discovered an extremely hard Xraycomponent, which can originate either from a kT virgul13 keV plasma orinverseCompton scattering. WR 140 will experience its periastron passage in2016 Dec., a critical time when the WWC emission changes dramatically. Wepropose joint NuSTAR and XMMNewton observations of WR 140 at key phases aroundperiastron in AO15, to determine the origin of this component and answer questions about the abrupt Xray flux decrease. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]