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    PR # 32259                                                                   
     We propose to measure the X-ray temperature and iron abundance of the       
     hot intracluster gas in the most distant (z=0.83), X-ray luminous           
     cluster of galaxies known, MS1054-03. We have already observed a            
     cluster at z=0.55, and found that while Tx was consistent with Lx for       
     the local Tx-Lx relation, the metallicity and gas-to-total mass ratio       
     were lower.  The high redshift provides a long lever arm to test            
     models for the evolution of the intracluster medium and cluster             
     formation.  The cluster is sufficiently bright and compact for ASCA         
     spectra; the redshift moves the interesting part of the spectra to ~4       
     KeV.  It is chosen from a well-defined X-ray selected cluster sample.       
     We have supplementary data from ROSAT, ground-based observatories,          
    the VLA, and proposed HST WFPC                                               
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