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    PR # 31045                                                                   
     Many black hole binaries show an ultrasoft spectrum when they are X-r       
     ay luminous. This ultrasoft component has been interpreted to be the        
     emission from an accretion disk extending to close vicinity of black        
     hole. If the iron line shows a double horn profile characteristic of        
     the relativistic disk, the above interpretation is firmly verified. T       
     his verification is crucial to identify black holes from the spectral       
      analysis with the multicolor blackbody disk model, for the cases in        
     which optical mass functions are not available. Previous observation        
     of GX 339-4 with GINGA detected the iron line during ultrasoft state        
     therefore it is a good target for this study.                               
                                                                                 
                                                                                 
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