Schedule Feb 09, 2006
Electron Heating and Acceleration in Gamma-Ray Bursts
Matthew Baring (Rice Univ.)

The principal paradigm for gamma-ray bursts (GRBs) suggests that the prompt transient gamma-ray signal arises from multiple shocks internal to the relativistic expansion. Since this signal is most probably electromagnetic in origin, a major issue concerns how the electrons get energized and accelerated in burst environments. This paper explores this issue of electron heating/acceleration at relativistic shocks that pertain to GRB models. Spectral fits to BATSE/EGRET burst data indicate that the preponderance of electrons that are responsible for the prompt emission reside in an intrinsically non-thermal population. Thisdiffers markedly from typical populations generated in acceleration simulations; potential resolutions of this conflict such as the action of self-absorption are discussed. In addition, the spectral analysissuggests that the synchrotron mechanism is favored over synchrotron self-Compton scenarios due to the latter$apos;s characteristically broad curvature near the spectral \"peak.\" The merits of other emission processes are also touched upon. A connection of this data interpretation to heating in the shock layer is then made. Expectations for heating of electrons from cross shock electrostatic potentials are presented, exploring the capability of relativistic shocks to generate predominantly non-thermal electron distributions from thermal poolsupstream. Constraints that the EGRET power-law indices provide on the shock parameters will also be discussed.

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