Prompt and afterglow emission from the X-ray-rich GRB 981226 observed withBepposax

We discuss observations of the prompt X- and gamma-ray emission and X-ray a fterglow from GRB 981226. This event has the weakest gamma-ray peak flux de tected with the BeppoSAX Gamma-Ray Burst Monitor. It shows an isolated X-ra y 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 th e BeppoSAX Narrow Field Instruments, and the X-ray afterglow was detected u p 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) x 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(-0.39)(+0.44). We discuss these results in the light of the current GRB models.