We report on BeppoSAX simultaneous X- and γ-ray observations of the bright γ-ray burst (GRB) 990123. We present the broad-band spectrum of the prompt emission, including optical, X- and γ-rays, confirming the suggestion that the emission mechanisms at low and high frequencies must have different physical origins. We discuss the X-ray afterglow observed by the Narrow Field Instruments (NFIs) on board BeppoSAX and its hard-X-ray emission up to 60 keV several hours after the burst, in the framework of the standard fireball model. The effects of including an important contribution of inverse Compton scattering or modifying the hydrodynamics are studied.
|Number of pages||4|
|Journal||Nuovo Cimento della Societa Italiana di Fisica C|
|State||Published - 2005|