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   PR # 21137
     The observation of the multifrequency variability is good tool to   
    give the solution of the fundamental astrophysical problem,the origin
    of AGN continuum emission. We propose the ASCA observation of the    
    brightest BL Lac objects, PKS2155-304, with the simultaneous observat
    ions with IUE, EUVE and ROSAT, in order to: (1) investigate the stabi
    lity of UV-X-ray correlation over long time and the time lag, and (2)
    obtain the correlation of the X-ray flux versus X-ray spectral       
    indices in the ASCA wide energy band. This would open the view of the
    orgine of the enormous AGN power,as the mechenism of the relativistic
    -nonthermal-electron acceration and the structure of the relativistic
     jets.                                                               
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