Variation of microphysics in wind bubbles: an alternative mechanism for explaining the rebrightenings in GRB afterglows

TL;DR

This paper proposes a new model where variable microphysics shock parameters in wind bubble environments can explain rebrightenings in GRB afterglows, successfully fitting observed light curves.

Contribution

It introduces a novel approach allowing discontinuous microphysics parameters in wind bubble environments to account for rebrightenings in GRB afterglows.

Findings

Model reproduces rebrightenings in GRB 060206, 070311, 071010A.

Variable microphysics parameters can explain observed light curve features.

Wind bubble environment influences afterglow rebrightenings.

Abstract

Conventionally, long GRBs are thought to be caused by the core collapses of massive stars. During the lifetime of a massive star, a stellar wind bubble environment should be produced. Furthermore, the microphysics shock parameters may vary along with the evolution of the fireball. Here we investigate the variation of the microphysics shock parameters under the condition of wind bubble environment, and allow the microphysics shock parameters to be discontinuous at shocks in the ambient medium. It is found that our model can acceptably reproduce the rebrightenings observed in GRB afterglows, at least in some cases. The effects of various model parameters on rebrightenings are investigated. The rebrightenings observed in both the R-band and X-ray afterglow light curves of GRB 060206, GRB 070311 and GRB 071010A are reproduced in this model.