53 - GRB polarimetry with POET

Summary

POET (Polarimeters for Energetic Transients) represents a concept for a NASA Small Explorer (SMEX) satellite mission, whose principal scientific goal is to understand the structure of GRB sources through sensitive X-ray and γ-ray polarization measurements. The payload consists of two wide field-of-view (FoV) instruments: a low-energy polarimeter (LEP) capable of polarization measurements in the energy range from 2–15 keV and a high-energy polarimeter (Gamma-Ray Polarimeter Experiment or GRAPE) that would measure polarization in the 60–500 keV energy range. The POET spacecraft provides a rotating zenith-pointed platform for dealing with any residual systematic effects in the polarization response and for maximizing the exposure to deep space. POET would be capable of measuring statistically significant polarization (for polarization levels in excess of 20%) for ∼80 GRBs in a two-year mission. High-energy polarization data would also be obtained for SGRs, solar flares, pulsars and other sources of astronomical interest.

Introduction

Gamma-ray bursts (GRBs) are amongst the most energetic events in the universe, and have stimulated intense observational and theoretical research. Theoretical models indicate that a refined understanding of the inner structure of GRBs, including the geometry and physical processes close to the central engine, requires the exploitation of high-energy X-ray and γ-ray polarimetry. To date, observations have been of limited sensitivity and subject to poorly understood systematics. POlarimeters for Energetic Transients (POET) is a SMEX mission concept that is capable of measuring the high-energy polarization of GRBs and other sources of astronomical interest.