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   PR # 11147
     We selected optically bright high z QSO's considering that X-ray
    intensities of QSO's eventually correlates with optical brightness.
    It is possible for us to estimate ASCA count rates assuming the
    correlation between X-ray and optical intensities. This assumption is
    based on the past X-ray observations of QSO's. The z dependence of
    spectral index is expected from a Compton reflection model of X-ray
    spectrum.It is essential for CXB to understand the spectral structure
    of QSO's with z= 2 to 4.




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