090452

We propose an observation of the western edge region of W50 nebula hosting themicroquasar SS 433.It is still unclear whether W50 is produced by the interaction between the jetsand the supernova remnant of the SS 433 birth or by just the SS 433 jetsthemselves.The prime aim is to reveal the formation mechanism of W50 by distinguishingbetween thermal and non-thermal (synchrotron) emissions in the edge region ofW50.The second aim is to understand the particle acceleration processes in the jetpropagating in the nebula. We recently found a hint of particle re-acceleration occurring at the knot existing in the western jet. Using the large collecting area of XMM we make the re-acceleration clear by determining the change of the spectral slope of the synchrotron emission along the jet. [truncated! Please see actual data for full text]