Gamma-ray bursts and their afterglows: toward a unified model



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Although much progress has been made in our understanding of gamma-ray bursts (GRBs) and their afterglows in the last few decades, some critical questions remain unanswered. One of these questions regards the form in which energy is transported from the explosion to the site at which the gamma-rays are produced -- i.e. is the energy carried in the kinetic energy of electrons and/or protons, or is much of it stored in a magnetic field? This dissertation documents a series of attempts to more clearly understand the nature of GRB outflows. First, we explore the possibility that the GRB is produced by an external shock, created when a baryonic outflow is decelerated by the surrounding medium. Next, emission from the external reverse shock is used to try to determine if the GRB ejecta is pair enriched. We then use data from several interesting, Swift-detected GRBs pin down the GRB emission radius, bulk Lorentz factor, magnetic field strength, and electron energy. We end by describing our nearly model independent method of modeling the GRB radiation as a combination of synchrontron and synchrontron self-Compton. We find that the GRB is likely to be produced by the syncrontron self-Compton radiation mechanism and predict that the accompanying prompt optical emission should be very high. If bright optical radiation during the GRB is not found, we think that this is good evidence that the acceleration of electrons is taking place repeatedly on a short timescale, effectively ruling out shock-based acceleration models.