BL Lacertae: the multiwavelength campaign of 2000
  We present two BeppoSAX observations of BL Lacertae as part of a multiwavelength radio-to-TeV campaign. During the first observation we observe a faint Compton spectrum, while during the second, we detect a synchrotron spectrum with the highest [2-10] keV flux ever measured; above 10 keV an inverse Compton component begin to dominate. The synchrotron flux is very variable with time scales of 1 hr. We describe four different SED shifting the synchrotron peak both in frequency and flux intensity and we sketch a scenario in which a blob moves along a jet and can be located in or outside the BLR. This implies different radiative mechanism at work, SSC or external Compton, producing different high energy spectra. 
M. Ravasio (1), G. Tagliaferri (1), G. Ghisellini (1), M. Boettcher   (2,3), H.D. Aller (4), M.F. Aller (4), O. Mang (5), L....