Gamma-Ray Bursts: Temporal Scales and the Bulk Lorentz Factor

Abstract

For a sample of Swift and Fermi GRBs, we show that the minimum variability timescale and the spectral lag of the prompt emission is related to the bulk Lorentz factor in a complex manner: For small $\Gamma$'s, the variability timescale exhibits a shallow (plateau) region. For large $\Gamma$'s, the variability timescale declines steeply as a function of $\Gamma$ ($\delta T\propto {\Gamma }^{-4.05\pm 0.64}$). Evidence is also presented for an intriguing correlation between the peak times, t${}_p$, of the afterglow emission and the prompt emission variability timescale.

Accepted for publication in ApJ

References in corpus (2)

• A new method of determining the initial size and Lorentz factor of gamma-ray burst fireballs using a thermal emission component
• Uncovering the Intrinsic Variability of Gamma-ray Bursts

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