A Turbulent Model of Gamma-Ray Burst Variability

Abstract

A popular paradigm to explain the rapid temporal variability observed in gamma-ray burst (GRB) lightcurves is the internal shock model. We propose an alternative model in which the radiating fluid in the GRB shell is relativistically turbulent with a typical eddy Lorentz factor $\gamma_t$. In this model, all pulses in the gamma-ray lightcurve are produced at roughly the same distance $R$ from the center of the explosion. The burst duration is $\sim R/c\Gamma^2$, where $\Gamma$ is the bulk Lorentz factor of the expanding shell, and the duration of individual pulses in the lightcurve is $\sim R/c\Gamma^2\gamma_t^2$. The model naturally produces highly variable lightcurves with $\sim\gamma_t^2$ individual pulses. Even though the model assumes highly inhomogeneous conditions, nevertheless the efficiency for converting jet energy to radiation is high.