New Measurement Resolves Key Astrophysical Fe XVII Oscillator Strength Problem

Abstract

One of the most enduring and intensively studied problems of X-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA III synchrotron facility by increasing the resolving power two and a half times and the signal-to-noise ratio thousand-fold compared to our previous work. The Lorentzian wings had hitherto been indistinguishable from the background and were thus not modeled, resulting in a biased line-strength estimation. The present experimental oscillator-strength ratio $R_{\exp }=f_{3C}/f_{3D}=3.51(2{)}_{\mathrm{stat}}(7{)}_{\mathrm{sys}}$ agrees with our state-of-the-art calculation of $R_{\mathrm{th}}=3.55(2)$, as well as with some previous theoretical predictions. To further rule out any uncertainties associated with the measured ratio, we also determined the individual natural linewidths and oscillator strengths of 3C and 3D transitions, which also agree well with the theory. This finally resolves the decades-old mystery of Fe XVII oscillator strengths.

Main manuscript and supplemental material at https://journals.aps.org/prl/supplemental/10.1103/PhysRevLett.129.245001/LN17392_Supplemental_Material.pdf

References in corpus (13)

• The Quiescent Intracluster Medium in the Core of the Perseus Cluster
• CHIANTI -- an atomic database for emission lines -- Paper XVI: Version 10, further extensions
• The Heidelberg compact electron beam ion traps
• QED shifts in multivalent heavy ions
• Fe XVII X-ray Line Ratios for Accurate Astrophysical Plasma Diagnostics
• X-ray spectra of the Fe-L complex
• Astrophysical line diagnosis requires non-linear dynamical atomic modeling
• X-ray spectra of the Fe-L complex II: atomic data constraints from EBIT experiment and X-ray grating observations of Capella
• Spectral Implications of Atomic Uncertainties in Optically-thin Hot Plasmas
• Comprehensive Laboratory Measurements Resolving the LMM Dielectronic Recombination Satellite Lines in Ne-like Fe XVII Ions
• X-ray spectra of the Fe-L complex III: systematic uncertainties in the atomic data
• Non-Equilibrium Modeling of the Fe XVII 3C/3D ratio for an Intense X-ray Free Electron Laser
• Fe XVII $2p$-$3s$ line ratio diagnostic of shock formation radius in O stars

Cited by in corpus (6)

• pCI: a parallel configuration interaction software package for high-precision atomic structure calculations
• High-Precision Transition Energy Measurements of Neon-like Fe XVII Ions
• Natural-linewidth measurements of the 3C and 3D soft-x-ray transitions in Ni XIX
• QED calculations of the E1 transition amplitude in neon-like iron and nickel
• Dielectronic recombination studies on Fe${}^{2+}$
• Parts-per-million-accurate determination of the K$\alpha$ photoionization resonance of Be-like oxygen with resolution of its ${}^{16}$O-${}^{18}$O isotopic shift