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    PR # 32119                                                                   
     We propose to use ASCA to study the evolution of the CTB1 supernova         
     remnant.  Optical, radio, and previous X-ray data suggest that the          
     blast wave may recently have encountered a progenitor induced cavity        
     wall.  A second, unlikely, possibility is that the entire remnant is        
     in transition from the Sedov phase to "snow-plow" phase of evolution.       
     We will fit the ASCA data with predictions from our dusty shock wave        
     code to determine physical parameters from the central and northern         
     regions of the remnant.  These will be used to determine the                
     evolutionary epoch of CTB1.                                                 
                                                                                 
                                                                                 
                                                                                 
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