Prompt and Afterglow Emission from the X‐Ray–Rich GRB 981226 Observed withBeppoSAX

We discuss observations of the prompt X- and γ-ray emission and X-ray afterglow from GRB 981226. This event has the weakest gamma-ray peak flux detected with the BeppoSAX Gamma-Ray Burst Monitor. It shows an isolated X-ray precursor and the highest X-ray to gamma-ray fluence ratio measured thus far with the BeppoSAX Wide Field Cameras. The event was followed up with the BeppoSAX Narrow Field Instruments, and the X-ray afterglow was detected up to 10 keV. The afterglow flux is observed to rise from a level below the sensitivity of the MECS/LECS telescopes up to a peak flux of (5 ± 1) × 10 -13 ergs cm -2 s -1 in the 2-10 keV energy band. This rise is followed by a decline according to a power law with an index of 1.31 . We discuss these results in the light of the current GRB models.