Laboratory Measurements of X-Ray Emission from Highly Charged Argon Ions

• Published in: The Astrophysical journal Vol. 870; no. 1; pp. 21 - 28
• Main Authors: Bulbul, Esra, Foster, Adam, Brown, Gregory V., Bautz, Mark W., Beiersdorfer, Peter, Hell, Natalie, Kilbourne, Caroline, Kraft, Ralph, Kelley, Richard, Leutenegger, Maurice A., Miller, Eric D., Porter, F. Scott, Smith, Randall K.
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center The American Astronomical Society 01.01.2019; American Astronomical Society / IOP Publishing; IOP Publishing; Institute of Physics (IOP)
• Subjects: Argon; Argon ions; Astronomy; ASTRONOMY AND ASTROPHYSICS; Astrophysics; ATOMIC AND MOLECULAR PHYSICS; atomic data; Atomic theory; Computer simulation; Dark matter; Electron beams; Electron energy; Emission measurements; Fluctuations; Flux; Galactic clusters; Galaxies; Helium; Laboratories; Line spectra; line: identification; Lithium; methods: laboratory: atomic; Secondary emission; Systematics; techniques: spectroscopic; X ray spectrometers; X-ray emissions; X-ray measurements; X-rays: galaxies: clusters
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/aaee7d

Uncertainties in atomic models will introduce noticeable additional systematics in calculating the flux of weak dielectronic recombination (DR) satellite lines, affecting the detection and flux measurements of other weak spectral lines. One important example is the Ar xvii Heβ DR, which is expected to be present in emission from the hot intracluster medium of galaxy clusters and could impact measurements of the flux of the 3.5 keV line that has been suggested as a secondary emission from a dark matter interaction. We perform a set of experiments using the Lawrence Livermore National Laboratory's electron beam ion trap (EBIT-I) and the X-ray Spectrometer quantum calorimeter (XRS/EBIT) to test the Ar xvii Heβ DR origin of the 3.5 keV line. We measured the X-ray emission following resonant DR onto helium-like and lithium-like Argon using EBIT-I's Maxwellian simulator mode at a simulated electron temperature of Te = 1.74 keV. The measured flux of the Ar xvii Heβ DR lined is too weak to account for the flux in the 3.5 keV line, assuming reasonable plasma parameters. We, therefore, rule out Ar xvii Heβ DR as a significant contributor to the 3.5 keV line. A comprehensive comparison between the atomic theory and the EBIT experiment results is also provided.