******************************************************                         
    PR # 32183                                                                   
     We propose to observe with Asca the EUV-bright Seyfert galaxy Mkn           
     478.  This is the brightest Seyfert galaxy in the extreme                   
     ultraviolet, appearing as both the ROSAT WFC and the EUVE survey            
     source.  The X-ray emission from this object is quite soft, and is          
     likely to be of different origin than "normal" X-ray Seyferts.  Since       
     Mkn 478 is the the brigtest object of a class of "ultra-soft" AGN           
     (devoid of the hard X-ray emission), this observation should                
     constrain the emission mechanism for the soft excess : is it a              
     Compton tail of the accretion disk, or is it a signature of the             
     non-thermal pair cascade operating in the source?  In addition, by          
     tightly constraining the Fe K line strength, we will be able to             
    determine if there is a substa                                               
  ******************************************************