Polarization of prompt and afterglow emission of Gamma-Ray Bursts

TL;DR

This paper reviews how polarization measurements of gamma-ray burst emissions and afterglows can reveal jet composition, geometry, and test fundamental physics, based on recent theoretical models and observational data.

Contribution

It summarizes current theoretical scenarios and observational datasets for GRB polarization, highlighting their implications for jet composition and quantum gravity tests.

Findings

Polarization properties differ significantly between electromagnetic and kinetic energy outflows.

Observational datasets for prompt and afterglow polarization are now extensive.

Polarimetric measurements can provide insights into jet geometry and fundamental physics.

Abstract

Gamma-ray bursts and their afterglows are thought to be produced by an ultra-relativistic 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 prompt emission and afterglow polarization are also a powerful diagnostic of the jet geometry. Again, with subtle and hardly detectable differences in the output flux, we have distinct polarization predictions. In this review we briefly describe the theoretical scenarios that have been developed following the observations, and the now large observational datasets that for the prompt and the afterglow phases are available. Possible implications of polarimetric measurements for quantum gravity theory testing are discussed, and future perspectives for the field briefly mentioned.