Prompt and afterglow emission from the X-ray rich GRB981226 observed with BeppoSAX

Abstract

We discuss observations of the prompt X and gamma-ray emission and X-ray afterglow from GRB981226. This event has the weakest gamma-ray peak flux detected with the 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 Wide Field Cameras. The event was followed up with the 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) erg cm-2 s-1, in the 2-10 keV energy band. This rise is followed by a decline according to a power law with index of 1.31 (+0.44,-0.39). We discuss these results in the light of the current GRB models.