The Electron and Ion Equilibrium in Colliding Wind Plasma

The massive binary systems, Eta Car and WR140, emit strong hard Xrays from thewindwind collision (WWC). The joint XMM and NuSTAR observations of Eta Cararound periastron in AO13 presented detailed views of extreme hard Xrayemission from the star for the first time. The >10 keV slope has an excess fromthe thermal spectral model measured between 510 keV, suggesting that theelectrons and highly ionized iron ions are not in equilibrium, or reflectionemission is contaminated. We therefore propose to revisit Eta Car at orbitalphase virgul0.2 when the WWC is relatively stable. For comparison, we also propose toobserve WR140 at a similar orbital geometry, which does not show reflectionemission and whose stellar, orbital and wind parameters are precisely determined, to study the electron ion interaction. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]