A Turbulent Model of Gamma-Ray Burst Variability

Abstract

A popular paradigm to explain the rapid temporal variability observed in gamma-ray burst (GRB) light curves 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 light curve are produced at roughly the same distance \(R\) from the centre 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 light curve is \(\sim R/c \Gamma^2{\gamma^2}_t\). The model naturally produces highly variable light curves with \(\sim {\gamma^2}_t\) individual pulses. Even though the model assumes highly inhomogeneous conditions, nevertheless the efficiency for converting jet energy to radiation is high.