Prompt and Afterglow Emission from the X-Ray-Rich GRB 981226 Observed with BeppoSAX

We discuss observations of the prompt X- and c-ray emission and X-ray afterglow from GRB 981226. This event has the weakest gamma-ray peak —ux detected with the BeppoSAX Gamma-Ray Burst Monitor. It shows an isolated X-ray precursor and the highest X-ray to gamma-ray —uence ratio mea- sured 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 —ux is observed to rise from a level below the sensitivity of the MECS/LECS telescopes up to a peak —ux 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 We discuss these results in the light of the current GRB 1.31 ~0.390.44. models. Subject headings: gamma rays: burstsgamma rays: observationsshock wavesX-rays: general

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