Beaming and Jets in Gamma Ray Bursts
Copenhagen, August 12-30, 2002
Gamma Ray Bursts (GRBs) are among the most violent phenomena in the universe known to this date, and remain among outstanding mysteries of modern astrophysics. There is as yet no clear consensus on the physical mechanism that drives these phenomena. Many different models have been proposed. A general characteristic of most models is that they result in the accretion of a transient disk onto a black hole. One class of models involves collisions (or mergers) between neutron stars and/or black holes (in binary systems). A second class of models, the so-called collapsar models, are closely related to supernovae. A collapsar is defined to be a massive star whose iron core has collapsed to a black hole that is continuing to accrete at a very high rate.
One common feature of many of these models is that the energy release takes the form of collimated flows (beams, or jets). "Jets" describe highly collimated relativistic flows from the source while "beaming" in this case is a geometrical effect of special relativity (the relativistic beaming allows to see only a small angular extent of the flow). Since the energy budget assigned to a given GRB depends heavily on assumptions about the extent to which the flow is collimated (jet-like or beam-like), determining the reality and nature of the collimation in GRBs is becoming an important goal of future observations, simulations and theoretical models.
The goal is to offer a unique combination of opportunities for critical review of recent, major progress in issues of beaming and jets in GRBs, for active work and collaboration between the program participants, and for education of graduate students and postdoctoral research scientists.