Handling Background in IXPE polarimetric data

TL;DR

This paper proposes strategies for optimal background selection and rejection in IXPE X-ray polarimetric data analysis, demonstrated through a case study on the magnetar 4U 0142+61, to enhance polarimetric sensitivity.

Contribution

It introduces a guideline and rejection strategy for instrumental background in IXPE polarimetric data, improving sensitivity in X-ray polarization measurements.

Findings

Effective background rejection improves polarimetric sensitivity.

Strategies successfully applied to the 4U 0142+61 observation.

Enhanced data analysis methods for future IXPE observations.

Abstract

IXPE (Imaging X-ray Polarimetry Explorer) is a Small Explorer mission by NASA and ASI, launched on December 9$^{th}$ 2021, dedicated to investigating X-ray polarimetry allowing angular-, time- and energy-resolved observations in the 2--8 keV energy band. IXPE is in Science Observation phase since January 2022; it comprises of three identical telescopes with grazing-incidence mirrors, each one having in the focal plane a Gas Pixel Detector (GPD). In this paper, we present a possible guideline to obtain an optimal background selection in polarimetric analysis, and a rejection strategy to remove instrumental background. This work is based on the analysis of IXPE observations, aiming to improve as much as possible the polarimetric sensitivity. In particular, the developed strategies have been applied ``as a case study'' to the IXPE observation of the 4U 0142+61 magnetar.