To the surprise of many, Galama (University of Amsterdam) discovered a supernova explosion (SN1998bw) coincident with one of the two NFI sources and coincident in time with GRB to within a few days. The explosion occurred inside a relatively nearby galaxy (z=0.0085) which is in strong contrast to 5 other GRBs whose distance could be determined and which have a distance z>0.835. This implies a total gamma-ray energy output of only 1048 ergs, again in strong contrast to the cosmological bursts with outputs of up to 1054 ergs. This points to a different physical mechanism at work, as well as a diversity in GRBs.
The various error boxes of GRB 980425 overlayed on a DSS image. The large circle is the WFC error box. Courtesy Titus Galama (UvA).