%0 Journal Article
%T The 1.4 GHz light curve of GRB 970508
%A T. J. Galama
%A R. A. M. J. Wijers
%A M. Bremer
%A P. J. Groot
%A R. G. Strom
%A A. G. de Bruyn
%A C. Kouveliotou
%A C. R. Robinson
%A J. van Paradijs
%J Physics
%D 1998
%I arXiv
%R 10.1086/311424
%X We report on Westerbork 1.4 GHz radio observations of the radio counterpart to $\gamma$-ray burst GRB~970508, between 0.80 and 138 days after this event. The 1.4 GHz light curve shows a transition from optically thick to thin emission between 39 and 54 days after the event. We derive the slope $p$ of the spectrum of injected electrons ($dN/d\gamma_{e}\propto\gamma_{e}^{-p}$) in two independent ways which yield values very close to $p=2.2$. This is in agreement with a relativistic dynamically near-adiabatic blast wave model whose emission is dominated by synchrotron radiation and in which a significant fraction of the electrons cool fast.
%U http://arxiv.org/abs/astro-ph/9804190v1