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Paper: Fast X-ray Variability of PKS 2155-304: A Cross Correlation Analysis
Volume: 159, BL Lac Phenomenon
Page: 184
Authors: Treves, Aldo; Zhang, Y. H.; Celotti, A.; Tavecchio, F.; Maraschi, L.; Ghisellini, G.; Tagliaferri, G.; Chiappetti, L.; Pian, E.; Urry, C. M.
Abstract: PKS 2155-304 is the brightest blazar in X-rays and one of the strongest and best studied AGNs at these frequencies. It was monitored by the BeppoSAX for 2.5 days in November 1996 during the satellite Performance Verification phase. A further, 1.3 days long, BeppoSAX campaign on the source was accomplished in November 1997, simultaneously with an EGRET Target of Opportunity observation. In the latter occasion, the source was found in a very bright X-ray state. Cross-correlation of the X-ray light curves of 1996 in different energy ranges has shown that the flux at higher frequencies leads that at lower frequencies. The measured time lag between the light curves in the 0.1-1.5 keV and 3-10 keV energy intervals is ~3 hours. In 1997 the lag, if present, is <=3D 0.5 hours. The results are compared with those obtained through multiwavelength campaigns in November 1991 and May 1994.
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