X-ray spectra of the Fe-L complex

Liyi Gu, A. J. J. Raassen, Junjie Mao, Jelle de Plaa, Chintan Shah, Ciro Pinto, Norbert Werner, Aurora Simionescu, François Mernier, Jelle S. Kaastra

Research output: Contribution to journalArticle

Abstract

The Hitomi results on the Perseus cluster lead to improvements in our knowledge of atomic physics which are crucial for the precise diagnostic of hot astrophysical plasma observed with high-resolution X-ray spectrometers. However, modeling uncertainties remain, both within but especially beyond Hitomi's spectral window. A major challenge in spectral modeling is the Fe-L spectrum, which is basically a complex assembly of n>2 to n=2 transitions of Fe ions in different ionization states, affected by a range of atomic processes such as collisional excitation, resonant excitation, radiative recombination, dielectronic recombination, and innershell ionization. In this paper we perform a large-scale theoretical calculation on each of the processes with the flexible atomic code (FAC), focusing on ions of Fe XVII to Fe XXIV that form the main body of the Fe-L complex. The new data are found to be consistent within 20% with the recent individual R-matrix calculations for the main Fe-L lines. By further testing the new FAC calculations with the high-quality RGS data from 15 elliptical galaxies and galaxy clusters, we note that the new model gives systematically better fits than the current SPEX v3.04 code, and the mean Fe abundance decreases by 12%, while the O/Fe ratio increases by 16% compared with the results from the current code. Comparing the FAC fit results to those with the R-matrix calculations, we find a temperature-dependent discrepancy of up to ~10% on the Fe abundance between the two theoretical models. Further dedicated tests with both observed spectra and targeted laboratory measurements are needed to resolve the discrepancies, and ultimately, to get the atomic data ready for the next high-resolution X-ray spectroscopy mission.
LanguageEnglish
Number of pages24
JournalAstronomy and Astrophysics
Volume627
Early online date1 Jul 2019
DOIs
Publication statusPublished - 31 Jul 2019

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x rays
recombination
ionization
matrix
ion
atomic physics
high resolution
elliptical galaxies
radiative recombination
data quality
X-ray spectroscopy
modeling
excitation
astrophysics
ions
spectrometer
physics
assembly
code
spectrometers

Keywords

  • atomic data
  • atomic processes
  • clusters
  • spectroscopic
  • galaxies

Cite this

Gu, L., Raassen, A. J. J., Mao, J., Plaa, J. D., Shah, C., Pinto, C., ... Kaastra, J. S. (2019). X-ray spectra of the Fe-L complex. Astronomy and Astrophysics, 627. https://doi.org/10.1051/0004-6361/201833860
Gu, Liyi ; Raassen, A. J. J. ; Mao, Junjie ; Plaa, Jelle de ; Shah, Chintan ; Pinto, Ciro ; Werner, Norbert ; Simionescu, Aurora ; Mernier, François ; Kaastra, Jelle S. / X-ray spectra of the Fe-L complex. In: Astronomy and Astrophysics. 2019 ; Vol. 627.
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abstract = "The Hitomi results on the Perseus cluster lead to improvements in our knowledge of atomic physics which are crucial for the precise diagnostic of hot astrophysical plasma observed with high-resolution X-ray spectrometers. However, modeling uncertainties remain, both within but especially beyond Hitomi's spectral window. A major challenge in spectral modeling is the Fe-L spectrum, which is basically a complex assembly of n>2 to n=2 transitions of Fe ions in different ionization states, affected by a range of atomic processes such as collisional excitation, resonant excitation, radiative recombination, dielectronic recombination, and innershell ionization. In this paper we perform a large-scale theoretical calculation on each of the processes with the flexible atomic code (FAC), focusing on ions of Fe XVII to Fe XXIV that form the main body of the Fe-L complex. The new data are found to be consistent within 20{\%} with the recent individual R-matrix calculations for the main Fe-L lines. By further testing the new FAC calculations with the high-quality RGS data from 15 elliptical galaxies and galaxy clusters, we note that the new model gives systematically better fits than the current SPEX v3.04 code, and the mean Fe abundance decreases by 12{\%}, while the O/Fe ratio increases by 16{\%} compared with the results from the current code. Comparing the FAC fit results to those with the R-matrix calculations, we find a temperature-dependent discrepancy of up to ~10{\%} on the Fe abundance between the two theoretical models. Further dedicated tests with both observed spectra and targeted laboratory measurements are needed to resolve the discrepancies, and ultimately, to get the atomic data ready for the next high-resolution X-ray spectroscopy mission.",
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Gu, L, Raassen, AJJ, Mao, J, Plaa, JD, Shah, C, Pinto, C, Werner, N, Simionescu, A, Mernier, F & Kaastra, JS 2019, 'X-ray spectra of the Fe-L complex' Astronomy and Astrophysics, vol. 627. https://doi.org/10.1051/0004-6361/201833860

X-ray spectra of the Fe-L complex. / Gu, Liyi; Raassen, A. J. J.; Mao, Junjie; Plaa, Jelle de; Shah, Chintan; Pinto, Ciro; Werner, Norbert; Simionescu, Aurora; Mernier, François; Kaastra, Jelle S.

In: Astronomy and Astrophysics, Vol. 627, 31.07.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - X-ray spectra of the Fe-L complex

AU - Gu, Liyi

AU - Raassen, A. J. J.

AU - Mao, Junjie

AU - Plaa, Jelle de

AU - Shah, Chintan

AU - Pinto, Ciro

AU - Werner, Norbert

AU - Simionescu, Aurora

AU - Mernier, François

AU - Kaastra, Jelle S.

PY - 2019/7/31

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