Early Rebrightenings of X-ray Afterglows from Ring-Shaped GRB Jets

TL;DR

This paper proposes that early rebrightenings in GRB X-ray afterglows can be explained by a ring-shaped jet model, which accounts for observed long-lasting rebrightenings that other mechanisms struggle to reproduce.

Contribution

The study introduces a ring-shaped jet model to explain early rebrightenings in GRB afterglows, providing a new perspective on jet structure and afterglow features.

Findings

Ring-shaped jet model reproduces observed rebrightenings.

Explains long-duration rebrightenings better than other mechanisms.

Matches observations of specific GRBs like 051016B and 060109.

Abstract

Early rebrightenings at a post-burst time of 10^2 - 10^4 s have been observed in the afterglows of some gamma-ray bursts (GRBs). Unlike X-ray flares, these rebrightenings usually last for a relatively long period. The continuous energy injection mechanism usually can only produce a plateau in the afterglow light curve, but not a rebrightening. Also, a sudden energy injection can give birth to a rebrightening, but the rebrightening is a bit too rapid. Here we argued that the early rebrightenings can be produced by the ring-shaped jet model. In this scenario, the GRB outflow is not a full cone, but a centrally hollowed ring. Assuming that the line of sight is on the central symmetry axis of the hollow cone, we calculate the overall dynamical evolution of the outflows and educe the multiband afterglow light curves. It is found that the early rebrightenings observed in the afterglows of a few GRBs, such as GRBs 051016B, 060109, 070103 and 070208 etc, can be well explained in this framework. It is suggested that these long-lasted early rebrightenings in GRB afterglows should be resulted from ring-shaped jets.