ar X iv : a st ro - p h / 04 06 27 7 v 2 1 3 Ju n 20 04 The Apparent Size of GRB Afterglows as a Test of the Fireball Model

ar X iv : a st ro - p h / 04 06 27 7 v 1 1 1 Ju n 20 04 The Apparent Size of GRB Afterglows as a Test of the Fireball Model

Taylor et al. (2004) reported recently on the first direct measurement of the apparent size of a GRB afterglow. Here we confront these observations with the predictions of the fireball model. We use a simple model to study numerically the evolution of the fireball and determine its apparent size, starting at the early spherical expansion phase through the jet break and into the Newtonian regime...

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ar X iv : a st ro - p h / 02 06 42 3 v 1 2 4 Ju n 20 02 EARLY GRB AFTERGLOWS REVISITED

The standard afterglow model neglects the presence of the GRB prompt radiation ahead of the blast wave. In fact, the blast wave is dramatically influenced by the leading gamma-ray front which preaccelerates the ambient medium and loads it with electron-positron pairs. The front sweeps the medium outward with a high Lorentz factor and results in a spectacular effect: the GRB ejecta moves freely ...

ar X iv : a st ro - p h / 03 02 17 7 v 1 1 0 Fe b 20 03 Polarization in GRB Afterglows

ar X iv : a st ro - p h / 05 06 13 9 v 2 2 1 Ju l 2 00 5 A Reverse - Shock Model for the Early

The prompt localization of gamma-ray burst (GRB) 050525A by Swift allowed the rapid follow-up of the afterglow. The observations revealed that the optical afterglow had a major rebrightening starting at ∼ 0.01 days and ending at ∼ 0.03 days, which was followed by an initial power-law decay. Here we show that this early emission feature can be interpreted as the reverse shock emission superposed...