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    PR # 31547                                                                   
     A1763 is a relatively distant, X-ray luminous cluster of galaxies in        
     which the baryon content, measured from the ratio of the X-ray emit-        
     ing gas o total mass, is 20 per cent within 1.8 Mpc. If Omega_0=1,  t       
     his conflicts with Big Bang nucleosynthesis which constrains the  the       
      baryon content to be <0.06h_{50}**{-2}. We propose to investigate th       
     e baryon fraction at large adius, requiring tight constraints on  the       
      X-ray gas temperature. In particular we wish to see if the ratio con       
     tinues to rise with radius, or decreases to a value consistent with t       
     he theoretically expected mean value for the Universe, at large radiu       
     s. ASCA provides the only means by which the spatial  variation of th       
     e X-ray temperature, and thereby the total mass and baryon fraction o       
    f A1763 can be tightly constra                                               
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