The unusual supernova SN1998bw , which is thought to be related to the \gamma -ray burster GRB980425 , is a possible link between the two classes of objects .
Analyzing the extensive radio emission data avaliable for SN1998bw , we are able to describe its time evolution within the well established framework available for the analysis of radio emission from supernovae .
This then allows description of a number of physical properties of the object .
The radio emission can best be explained as interaction of a mildly relativistic ( \Gamma \sim 1.6 ) shock with a dense pre-explosion stellar wind established circumstellar medium ( CSM ) which is highly structured both azimuthally , in clumps or filaments , and radially , with two observed density enhancements separated by \sim 3 \times 10 ^ { 17 } cm .
With assumptions as to pre-explosion stellar wind conditions , it is possible to estimate that the progenitor to SN 1998bw had a mass loss rate of \sim 3.5 \times 10 ^ { -5 } { M _ { \odot } } ~ { } { yr } ^ { -1 } with at least two \sim 30 \% increases in mass-loss rate ; the most recent extending from \sim 1 , 600 - 4 , 700 yr before explosion and the oldest known having occurred , with possibly comparable length , \sim 12 , 000 yr before explosion .
Because of its unusual characteristics for a Type Ib/c SN , the relation of SN1998bw to GRB980425 is strengthened with consequent improvement in our understanding of these poorly understood objects .