Diverse Features of the Multi-wavelength Afterglows of Gamma-ray Bursts: Natural or Special?

TL;DR

This paper reviews a numerical method for modeling GRB afterglows and links diverse optical and X-ray features to different central engine mechanisms, offering new insights into GRB physics.

Contribution

It introduces a numerical approach to explain diverse afterglow features and relates them to specific central engine activities in GRBs.

Findings

Steep optical re-brightenings caused by fall-back accretion in black holes.

Shallow optical re-brightenings due to electron-positron wind injection from magnetars.

Provides methods to probe GRB central engine characteristics.

Abstract

The detection of optical re-brightenings and X-ray plateaus in the afterglows of gamma-ray bursts (GRBs) challenges the generic external shock model. Recently, we have developed a numerical method to calculate the dynamic of the system consisting of a forward shock and a reverse shock. Here, we briefly review the applications of this method in the afterglow theory. By relating these diverse features to the central engines of GRBs, we find that the steep optical re-brightenings would be caused by the fall-back accretion of black holes, while the shallow optical re-brightenings are the consequence of the injection of the electron-positron-pair wind from the central magnetar. These studies provide useful ways to probe the characteristics of GRB central engines.