Thermal Emission or Charge Exchange from the North Polar Spur

We propose a coupled observation of the North Polar Spur (NPS) and a nearbyoffspur region in order to determine whether the soft Xray spectrum of the NPSis solely produced by hot plasma thermal emission, or whether some fraction ofthe emission is produced by charge exchange (CX) collisions between neutralparticles and ions within the hot gas envelope of the Loop I/NPS superbubble.Our goal is to confirm and measure the shift in energy of the Helike O VII andNe IX triplet centroids measured at low significance in previous observations ofthe NPS with XMMNewton and Suzaku. These shifts are predicted by the CXemission models but not in thermal emission models. We request the new ON/OFFobservations of the NPS in order to avoid large spatial variations of the cosmic background truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]