Linear and circular polarimetry observations of GRB afterglows

TL;DR

This paper reviews recent advances in polarimetry observations of GRB afterglows, highlighting how polarization measurements reveal magnetic field structures and jet geometries, especially during jet breaks.

Contribution

It provides a comprehensive review of late-time polarimetry techniques and presents new observational results, emphasizing the role of polarization in understanding GRB jet physics.

Findings

Polarimetry helps diagnose magnetic field properties in GRB afterglows.

Jet breaks are associated with specific polarization signatures.

New instruments are improving the quality and quantity of polarimetric data.

Abstract

Follow-up observations of large numbers of gamma-ray burst (GRB) afterglows, facilitated by the Swift satellite, have produced a large sample of spectral energy distributions and light curves, from which the basic micro- and macrophysical parameters of afterglows may be derived. However, a number of phenomena have been observed that defy explanation by simple versions of the standard fireball model, leading to a variety of new models. Polarimetry has shown great promise as a diagnosis of afterglow physics, probing the magnetic field properties of the afterglow and geometrical effects (e.g. jet breaks). Unfortunately, high quality polarimetry of a significant sample of afterglows is difficult to acquire, requiring specialised instrumentation and observing modes. In this paper I will review the recent successes in late-time afterglow polarimetry, also showing first results of new instruments and observing campaigns. I will particularly focus on jet breaks.