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    PR # 31102                                                                   
     We propose to observe 3C397 and W51.  These two SNRs are known as she       
     ll-type in the radio band while they show irregular shape in X-ray. T       
     hey are not well studied in the past while they are strong enough to        
     be observed with Asca.  SNR can be mainly divided into two groups. On       
     e is a shell type SNR that has a thermal emission converting the kine       
     tic energy of the shell.  The other is a Crab-like (centerfilled type       
     ) SNR that has a synchrotron emission converting the rotation energy        
     of the neutron star.  There is no point source in radio for both SNRs       
     .  The purpose is to detect line emissions that will prove the emissi       
     on origion of these SNR to be thin thermal.  We want to establish tha       
     t the X-ray spectrum is more important than the morphology.                 
                                                                                 
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