Summary of Thesis work results

The BeppoSAX Gamma-Ray Burst Monitor, which had in design and realization stage a lower priority with respect to the other experiments on-board the satellite, thanks to the work described in this Thesis, can be used to perform photometry and spectroscopy in the hard X-ray band. GRB broad band study and spectral evolution are unprecedented results having a relevant scientific impact in the field. Indeed, also if GRB X, optical and radio afterglows have undergone a quite rapid comprehension and interpretation just few months after their discovery, the burst event itself remains an elusive object. The measurements reported in chapter 5, and in particular the study of rapid spectral variability by the joint use of GRBM and WFC data, can surely contribute to the improvement of the following topics in GRB science:

• in the frame of the synchrotron shock models: diagnostic of the parameters of the shock and study of the relative role of external/internal forward/reverse shocks;
• testing the possible presence of (Photoelectric, Compton or Self-Synchrotron) absorption, particularly in the first instants of the GRB;
• contribution to the evaluation of the total luminosity of the prompt event;
• study of the transition from the GRB to the afterglow, also to evaluate the total energy content.

The analysis of the data of the giant outburst of SGR1900+14 has provided another instance of the capabilities of GRBM. In presence of a strong signal also the GRBM itself, without the simultaneous data of WFC, can provide information of extreme value: in this case the high sensitivity measurement of the pulse structure, the peculiar hardness ratio and the average spectra, with clear evidence of the hard component.