X-Ray Polarization Study of Pulsar Wind Nebulae with eXTP: Simulation Results and Scientific Prospects

TL;DR

This study evaluates the enhanced eXTP mission's X-ray polarization capabilities for pulsar wind nebulae, demonstrating improved sensitivity and broader observational prospects compared to previous missions like IXPE.

Contribution

It develops a simulation framework for eXTP PFA observations, quantifies its improved polarization detection sensitivity, and assesses its potential to expand PWN polarization studies.

Findings

eXTP offers about twice the sensitivity of IXPE in polarization detection.

For bright PWNe, 1 Ms observations reach polarization detection thresholds of 4-5%.

eXTP's capabilities will significantly increase the number of PWNe with measurable X-ray polarization.

Abstract

X-ray polarization observations of pulsar wind nebulae (PWNe) provide crucial insights into magnetic field structures and particle acceleration mechanisms. While the Imaging X-ray Polarimetry Explorer (IXPE) has made significant contributions to PWN studies, its limited effective area restricts observations to only the brightest sources, leaving many fainter nebulae unexplored. We evaluate the polarization capabilities of the enhanced X-ray Timing and Polarimetry mission (eXTP) for studying PWNe and establish a methodology for simulating eXTP Polarimetry Focusing Array (PFA) observations using modified IXPEOBSSIM. We develop and validate a simulation framework with appropriate response functions and instrumental background models, conducting comprehensive simulations of twelve PWNe selected from the SNRcat catalogue across various evolutionary stages and brightness levels. Our simulations demonstrate that eXTP provides approximately a factor of 2 improvement in minimum detectable polarization at the 99\% confidence level (MDP$_{99}$) compared to IXPE. For the brightest targets (N157B, G54.1+0.3, and Mouse), 1 Ms observations achieve MDP$_{99}$ values of 4-5\%. The area with significant polarization detection for extended sources like Vela PWN is nearly twice as large as achievable with IXPE. These enhanced capabilities will significantly expand the sample of PWNe with robust X-ray polarization measurements, enabling systematic studies of magnetic field structures, particle acceleration mechanisms, and PWN-environment interactions across different evolutionary phases.