An Unfolding Method for X-ray Spectro-Polarimetry

TL;DR

This paper introduces an iterative unfolding method for X-ray spectro-polarimetry that accurately reconstructs energy spectra and polarization properties from complex, biased measurements, demonstrated through simulated data.

Contribution

The paper presents a novel iterative unfolding algorithm that simultaneously reconstructs energy spectra and polarization properties in X-ray polarimetry.

Findings

Successfully recovers energy spectrum from simulated data.

Accurately estimates energy-dependent polarization fraction.

Handles biases from detector response and atmospheric absorption.

Abstract

X-ray polarimetry has great scientific potential and new experiments, such as X-Calibur, PoGOLite, XIPE, and GEMS, will not only be orders of magnitude more sensitive than previous missions, but also provide the capability to measure polarization over a wide energy range. However, the measured spectra depend on the collection area, detector responses, and, in case of balloon-borne experiments, the absorption of X-rays in the atmosphere, all of which are energy dependent. Combined with the typically steep source spectra, this leads to significant biases that need to be taken into account to correctly reconstruct energy-resolved polarization properties. In this paper, we present a method based on an iterative unfolding algorithm that makes it possible to simultaneously reconstruct the energy spectrum and the polarization properties as a function of true photon energy. We apply the method to a simulated X-Calibur data set and show that it is able to recover both the energy spectrum and the energy-dependent polarization fraction.