A Study of background for IXPE

TL;DR

This paper models the expected background noise for IXPE using Monte Carlo simulations, assessing its impact on observations of point and extended X-ray sources, and explores background rejection techniques.

Contribution

It provides the first detailed simulation-based estimate of IXPE's background and evaluates its effects on faint and extended X-ray source observations.

Findings

Background is 2.9 times larger than required but negligible for point sources.

Background impacts supernova remnant observations, requiring subtraction.

Monte Carlo simulations effectively model the background environment.

Abstract

Focal plane X-ray polarimetry is intended for relatively bright sources with a negligible impact of background. However this might not be always possible for IXPE (Imaging X-ray Polarimetry Explorer) when observing faint extended sources like supernova remnants. We present for the first time the expected background of IXPE by Monte Carlo simulation and its impact on real observations of point and extended X-ray sources. The simulation of background has been performed by Monte Carlo based on GEANT4 framework. The spacecraft and the detector units have been modeled, and the expected background components in IXPE orbital environment have been evaluated. We studied different background rejection techniques based on the analysis of the tracks collected by the Gas Pixel Detectors on board IXPE. The estimated background is about 2.9 times larger than the requirement, yet it is still negligible when observing point like sources. Albeit small, the impact on supernova remnants indicates the need for a background subtraction for the observation of the extended sources.