GRB Afterglow Polarimetry: Past, Present and Future

TL;DR

This paper reviews the history, current state, and future directions of gamma-ray burst afterglow polarimetry, emphasizing its role in understanding jet composition and geometry.

Contribution

It highlights the potential of polarization measurements to distinguish between different jet compositions and geometries in GRB afterglows, and discusses future observational prospects.

Findings

Polarization properties differ significantly between kinetic and electromagnetic outflows.

Afterglow polarization evolution provides insights into jet geometry.

Polarimetry can help resolve the jet composition debate in GRBs.

Abstract

Gamma-ray bursts and their afterglows are thought to be produced by an ultrarelativistic jet. One of the most important open questions is the outflow composition: the energy may be carried out from the central source either as kinetic energy (of baryons and/or pairs), or in electromagnetic form (Poynting flux). While the total observable flux may be indistinguishable in both cases, its polarization properties are expected to differ markedly. The later time evolution of afterglow polarization is also a powerful diagnostic of the jet geometry. Again, with subtle and hardly detectable differences in the output flux, we have distinct polarization predictions.