SHOCKED BY GRB-970228 - THE AFTERGLOW OF A COSMOLOGICAL FIREBALL

The location accuracy of the BeppoSAX Wide Field Cameras and acute gro undbased follow-up have led to the detection of a decaying afterglow i n X-rays and optical light following the classical gamma-ray burst GRB 970228. The afterglow in X-rays and optical light fades as a power la w at all wavelengths. This behaviour was predicted for a relativistic blast wave that radiates its energy when it decelerates by ploughing i nto the surrounding medium. Because the afterglow has continued with u nchanged behaviour for more than a month, its total enegy must be of o rder 10(51) erg, placing it firmly at a redshift of order 1. Further t ests of the model are discussed, some of which can be performed with a vailable data, and implications for future observing strategies are po inted out. We discuss how the afterglow can provide a probe for the na ture of the burst sources.