X-ray spectra of the Fe-L complex III: systematic uncertainties in the atomic data

TL;DR

This paper introduces a new method to estimate systematic uncertainties in atomic data for X-ray plasma models, using high-resolution spectra from stellar and galaxy sources, impacting temperature and abundance measurements.

Contribution

The study presents a novel approach to quantify atomic data uncertainties in plasma models based on observed spectra, addressing a gap in current theoretical calculations.

Findings

Systematic uncertainties show anti-correlation with model line fluxes.

Strong lines are better reproduced, indicating higher atomic data accuracy.

Uncertainties impact temperature estimates by 1-2% and abundances by 3-20%.

Abstract

There has been a growing request from the X-ray astronomy community for a quantitative estimate of systematic uncertainties originating from the atomic data used in plasma codes. Though there have been several studies looking into atomic data uncertainties using theoretical calculations, in general, there is no commonly accepted solution for this task. We present a new approach for estimating uncertainties in the line emissivities for the current models of collisional plasma, mainly based upon dedicated analysis of observed high resolution spectra of stellar coronae and galaxy clusters. We find that the systematic uncertainties of the observed lines consistently show anti-correlation with the model line fluxes, after properly accounting for the additional uncertainties from the ion concentration calculation. The strong lines in the spectra are in general better reproduced, indicating that the atomic data and modeling of the main transitions are more accurate than those for the minor ones. This underlying anti-correlation is found to be roughly independent on source properties, line positions, ion species, and the line formation processes. We further apply our method to the simulated XRISM and Athena observations of collisional plasma sources and discuss the impact of uncertainties on the interpretation of these spectra. The typical uncertainties are 1-2% on temperature and 3-20% on abundances of O, Ne, Fe, Mg, and Ni.