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   71181
   The optical depth of He-like Fe-Ka emission lines in an intracluster
   medium is derived from the intensity ratio of He-Like/H-like Ka, Ka/Kb
   and Fe-L/Fe-K, which is due to the resonance scattering effect. It
   results in increasing Fe abundance by a factor of two at most and
   becomes a key parameter to derive the Hubble constant. A3558(z=0.0482)
   is selected for this purpose under criteria of high intensity,
   temperature of 5-7keV, isothermality and large angular size fit well to
   GIS field of view. We need long exposure for detailed spectral analysis
   of Fe-K lines.
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