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   71187
   HCG 15 is one of the loosest group among Hickson xompact groups (HCGs).
   A HCG can be regarded as one stage in dynamical evolution of initially
   more extended system. According to this idea, a looser HCG has less
   evolved and its mass should show less concentration towrd the group
   center while a denser one has more evolved and strong mass
   concentration toward the group center should realize. Thus, it is
   expected that the spatial mass distribution in a HCG which is obtained
   by X-ray observation of hot intragroup gas can be used as an indicator
   of stages of dynamical evolution of HCGs. However, unfortunately,
   actual spatial distribution of mass in a loose HCG is little known at
   present. With this motivation, we propose a 100 ksec ASCA SIS
   observation of HCG 15.
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