X-ray spectra of the Fe-L complex

III. Systematic uncertainties in atomic data^★

¹ SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
e-mail: l.gu@sron.nl
² RIKEN High Energy Astrophysics Laboratory, 2-1 Hirosawa, Wako, Saitama, 351-0198 Japan
³ NASA/Goddard Space Flight Center, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA
⁴ Max-Planck-Institut für Kernphysik, Heidelberg, 69117 Heidelberg, Germany
⁵ Department of Physics, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8526 Japan
⁶ Department of Physics, University of Strathclyde, Glasgow, G4 0NG UK
⁷ Astronomical Institute “Anton Pannekoek”, Science Park 904, 1098 XH Amsterdam, University of Amsterdam, The Netherlands
⁸ INAF – IASF Palermo, Via U. La Malfa 153, 90146 Palermo PA, Italy
⁹ Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlářská 2, Brno, 611 37 Czech Republic
¹⁰ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
¹¹ Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa, 277-8583 Japan
¹² ESTEC/ESA, Keplerlaan 1, 2201AZ Noordwijk, The Netherlands
¹³ Laboratory of Instrumentation, Biomedical Engineering and Radiation Physics (LIBPhys-UNL), Department of Physics, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
¹⁴ Space Science Laboratory, University of California, Berkeley, CA 94720 USA

Received: 20 November 2020
Accepted: 14 June 2022

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 a 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 an anticorrelation 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 anticorrelation is found to be roughly independent of source properties, line positions, ion species, and the line formation processes. We further applied 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.