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   PR # 12070
    The soft Xray emission seen shortly after a TypeII supernova event is
    usually attributed to a reverse shock propagating into the exploded
    stellar envelope.An attractive alternative model suggests that the X-
    rays arise from shocks propagating into dense clouds in the pre-exist
    ing stellar wind.The widths of the emission lines are dramatically
    different in the two models,being less than 600km/sec in the cloud
    model & 20,000-30,000 km/sec in the reverse shock model.  Our simulat
    ions indicate that the SIS would easily reveal lines broader than
    9,000km/sec,so we propose SIS observations that will discriminate bet
    ween the two models.Also,these observations will accurately determine
    the X-ray temperature,luminosity,and metalicity,which provide crucial
   constraints on any model.
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