RELATIVISTIC PRECESSING JETS AND COSMOLOGICAL GAMMA-RAY BURSTS

We discuss the possibility that gamma-ray bursts may result from cosmo logical relativistic blob-emitting neutron star jets that precess past the line of sight. Beaming reduces the energy requirements, so that t he jet emission can last longer than the observed burst duration. One precession mode maintains a short-duration timescale while a second ke eps the beam from returning to the line of sight, consistent with the paucity of repeaters. The long life of these objects reduces the numbe r required for production as compared to short-lived jets. Blobs can a ccount for the time structure of the bursts. Here we focus largely on kinematic and timescale considerations of beaming, precession, and blo bs-issues that are reasonably independent of the acceleration and jet collimation mechanisms. We do suggest that large amplitude electromagn etic waves could be a source of blob acceleration.