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   PR # 21036
    Unique absorption-line features around 4.1 keV have been detected in 
    the burst spectra from at least three low-mass X-ray binaries.  If   
    they are a gravitationally redshifted atomic line and the responsible
    element is identified,the observed redshift factor will directly give
    the mass to radius ratio of the neutron stars.  We propose a detailed
    investigation of the  absorption line for the bursts from X1636-53   
    with high spectral resolution of  the ASCA SIS.  Since this investiga
    tion has been identified as one of the most important objectives of  
    SCA and also requires a long exposure time, we propose it as a       
    special group-project.                                               
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