TIME RESOLVED SPECTRA OF GRBs SIMULTANEOUSLY DETECTED WITH BATSE andBeppoSAX WFCs

We will discuss preliminary results of a systematic investigation devoted to study the time resolved broad-band spectra of the prompt emission of a sample of GRBs. These events were simultaneously detected with the BeppoSAX WFCs and the BATSE instrument aboard CGRO. We will discuss the fit of these spectra with the Band function, with a blackbody plus a power–law model, and with a Comptonization model developed by Titarchuk & Farinelli (2011, to be submitted).