XMM observed the BL Lac PKS 2155-304 for a full orbit (about 150 ksec) on 2000 November 19-21. Preliminary results on the temporal and spectral analysis of data from the EPIC PN camera and Optical Monitor are presented. The variability amplitude depends systematically on energy, however the slopes of the structure functions of the light-curves in different bands do not appear to be significantly different. No evidence of time lags is found by cross correlating the light-curves in different bands.
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