GRANAT/SIGMA Observations of Early Afterglows from Gamma-Ray Bursts in Soft Gamma-Rays

We present the search for early, soft gamma-ray afterglows in the set of hard-long gamma-ray bursts that were detected by the SIGMA telescope aboard GRANAT. One of these bursts is of paticular interest since it shows a smooth transition from the main event into an afterglow where flux decays as a power law. We also observe an abrupt change in spectral behavior at the transition between the main GRB event and its afterglow. All these observations are discussed in connection will the relativistic fireball models of gamma-ray bursts.