Plug Disintegration in GRB Jet Eruption

TL;DR

This paper models the dynamics of a baryonic plug in a relativistic GRB jet, showing how it breaks up due to Rayleigh-Taylor instability and influences late-time GRB features.

Contribution

It introduces a relativistic hydrodynamic model for jet plug disintegration and demonstrates its role in explaining GRB late-time phenomena.

Findings

The plug breaks up at a radius larger than the envelope due to Rayleigh-Taylor instability.

Post-breakup, the jet accelerates to higher Lorentz factors while fragments have moderate speeds.

Slower ejecta from the plug can explain X-ray flares in GRBs.

Abstract

In this work we consider the eruption of a tenuous relativistic hydrodynamic jet from a dense baryonic envelope. As the jet moves out and away, it carries along and continues to accelerate a layer of baryonic material which we refer to as the plug. We solve the relativistic equations of motion for the trajectory of the plug, and verify it using a relativistic hydrodynamic simulation. We show that under these conditions, the plug breaks up at a radius larger by a factor of a few from the radius of the envelope, due to the onset of the Rayleigh Taylor instability. After breakup the jet continues to accelerate to higher Lorentz factors while the plug fragments maintain a moderate Lorentz factor. The presence of slower moving ejecta can explain late time features of GRBs such as X ray flares without recourse to a long lived engine.