High Energy Polarimetry of Prompt GRB Emission

TL;DR

This paper reviews the current state of high-energy gamma-ray polarization measurements in GRBs, discussing observational challenges and the implications for understanding magnetic fields and emission mechanisms.

Contribution

It provides a comprehensive review of polarization observations in GRBs, emphasizing instrumental issues and insights for future research.

Findings

Most GRBs may have high polarization levels (>50%)

Current data suggest synchrotron emission with ordered magnetic fields

Observational limitations hinder definitive conclusions

Abstract

Evidence of polarized $\gamma$-ray emission ($>$ 50 keV) from Gamma-Ray Bursts (GRBs) has been accumulated in recent years. Measurements have been reported with levels in the range of 30-80\%, typically with limited statistical significance. No clear picture has yet emerged with regards to the polarization properties of GRBs. Taken at face value, the data suggest that most GRBs have a relatively large level of polarization (typically, $> 50\%$), which may suggest synchrotron emission associated with an ordered magnetic field structure within the GRB jet. But these results are far from conclusive. Here, we review the observations that have been made, concentrating especially on the instrumental issues and the lessons that might be learned from these data.