THE QUEST OF THE SHOCK IN THE MERGING CLUSTER A3667

One of the interesting chandra discoveries is the existence of sharp gas densityedges in some galaxy clusters. There are two different types of such features,depending on the sign of their temperature jump: a cold front and a mergerbowshock. A3667 is the most striking example of cold front and with a possibleevidence of a bow shock. Existing chandra and xmm observation do not allow tofirmly establish the nature of the outer surface brightness jump: we thuspropose a long onaxis observation to exploit the large effective area of EPICin order to measure the sign of the temperature jump across the outerdiscontinuity. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]