Gamma Ray Burst Prompt Emission Variability in Synchrotron and Synchrotron Self-Compton Lightcurves

摘要

Gamma Ray Burst prompt emission is believed to originate from electronsaccelerated in a highly relativistic outflow. "Internal shocks" due tocollisions between shells ejected by the central engine is a leading candidatefor electron acceleration. While synchrotron radiation is generally invoked tointerpret prompt gamma-ray emission within the internal shock model,synchrotron self-Compton (SSC) is also considered as a possible candidate ofradiation mechanism. In this case, one would expect a synchrotron emissioncomponent at low energies, and the naked-eye GRB 080319B has been considered assuch an example. In the view that the gamma-ray lightcurve of GRB 080319B ismuch more variable than its optical counterpart, in this paper we study therelative variability between the synchrotron and SSC components. We develop a"top-down" formalism by using observed quantities to infer physical parameters,and subsequently to study the temporal structure of synchrotron and SSCcomponents of a GRB. We complement the formalism with a "bottom-up" approachwhere the synchrotron and SSC lightcurves are calculated through a Monte-Carlosimulations of the internal shock model. Both approaches lead to the sameconclusion. Small variations in the synchrotron lightcurve can be onlymoderately amplified in the SSC lightcurve. The SSC model therefore cannotadequately interpret the gamma-ray emission properties of GRB 080319B.