The beaming angle (zeta) is the main uncertainty in gamma ray burst energy
requirements today. We summarize predictions for the light curves of beamed
bursts, and model the R band light curve of GRB 970508 to derive zeta > 30
degrees. This yields an irreducible minimum energy requirement of 3.4 times
10^{49} ergs to power the afterglow alone.Comment: 2 pages, one embedded postscript figure. To appear in Astronomy and
Astrophysics Supplement series (Rome conference proceedings issue). Uses "aa"
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