X-ray polarimetry in Astrophysics with the Gas Pixel Detector

TL;DR

The Gas Pixel Detector enables highly sensitive X-ray polarimetry in astrophysics by reconstructing photoelectron tracks, offering significant improvements over traditional methods and supporting multiple space missions.

Contribution

This paper introduces the Gas Pixel Detector's capabilities for X-ray polarimetry, highlighting its innovative track reconstruction and application in upcoming space telescopes.

Findings

Enhanced sensitivity in X-ray polarimetry compared to traditional techniques

Successful application in pathfinder missions POLARIX and HXMT

Inclusion in the baseline design of the IXO telescope

Abstract

The Gas Pixel Detector, recently developed and continuously improved by Pisa INFN in collaboration with IASF-Roma of INAF, can visualize the tracks produced within a low Z gas by photoelectrons of few keV. By reconstructing the impact point and the original direction of the photoelectrons, the GPD can measure the linear polarization of X-rays, while preserving the information on the absorption point, the energy and the time of individual photons. Applied to X-ray Astrophysics, in the focus of grazing incidence telescopes, it can perform angular resolved polarimetry with a huge improvement of sensitivity, when compared with the conventional techniques of Bragg diffraction at 45 degrees and Compton scattering around 90 degrees. This configuration is the basis of POLARIX and HXMT, two pathfinder missions, and is included in the baseline design of IXO, the very large X-ray telescope under study by NASA, ESA and JAXA.