Two BeppoSAX observations of BL Lac

G. Tagliaferri, G. Ghisellini, M. Ravasio, A. Celotti, M. Chiaberge, L. Chiappetti, L. Costamante, P. Giommi, L. Maraschi, E. Massaro, R. Nesci, C. M. Raiteri, F. Tavecchio, G. Tosti, A. Treves, M. Villata, A. Wolter

Published 2000-07-08Version 1

We present the results of two ToO BeppoSAX observations of BL Lac. During the first observation we detected both the synchrotron and the Compton components. Fast time variability was present, but only for the synchrotron component. During the second observation the spectrum was flatter and only the Compton component was present. Four different SED are presented and can be described by a blob moving along a jet and responsible for the SSC emission. The seed photons for the Compton scattering are the synchrotron photons themself plus possibly external photons coming from the broad line region.