The Beaming Factor and Other Open Questions In GRB Jets

Abstract

I review several central open questions concerning GRB Jets. 1) I discuss a new estimates of the beaming correction for the rate of GRBs ~ 75 +- 20. 2) I discuss the universal structured jet (USJ) model and conclude that while jets might be structured they are less likely to be universal. 3) I discuss recent observations of a sideways expansion of a GRB afterglow and compare these with current hydrodynamics simulations of jet evolution. 4) I discuss the implications of resent outliers to the energy-angle relation.

To appear in the proceedings of the Rome GRB meeting, Oct 2004. Typos corrected in the revised version