BeppoSAX Observations of PKS 2155-304 during an active Gamma-ray State
  PKS 2155-304 was observed with BeppoSAX in November 1997 for 64 ksec (total elapsed time 33.5 hours) and, for the first time, simultaneously in gamma-rays with EGRET on board the Compton Gamma Ray Observatory and with the ground based TeV telescope CANGAROO, during a phase of high brightness in the X-ray band. The LECS and MECS light curves show a pronounced flare (with an excursion of a factor 3.5 between min and max), with evidence of spectral hardening at maximum intensity. The source is weakly detected by the PDS in the 12-100 keV band with no significant evidence of variability. The broad band X-ray data from Beppo SAX are compared with the gamma-ray results and discussed in the framework of homogenous synchrotron self Compton models. 
L. Maraschi, L. Chiappetti, F. Tavecchio, A. Celotti, G. Fossati, G.   Ghisellini, P. Giommi, E. Pian, G. Tagliaferri, A. Tr...