High accuracy laboratory studies of x-ray emission from He-like ions for interpreting spectra from the X-ray Astrophysics Recovery Mission
Abstract
The launch and successful operation of the Soft X-ray Spectrometer (SXS) calorimeter instrument on the Hitomi X-ray observatory proved transformational. Although only a single high-statistics, high-resolution spectrum was measured, covering the broad energy range between 2 and 10 keV, the resulting advances of our understanding of the physics taking place in the cluster have been profound. During the analysis of the spectrum, however, it was found that many atomic parameters are not known to the accuracy necessitated by the high resolution SXS spectrum. For example, transition energies and line strengths found in the standard models were not adequate to interpret the Perseus spectrum, and in some cases significant differences between standard models exist, even in the case of strong lines in the helium-like K alpha complex of Fe24+. Some of the problems were addressed using existing laboratory data, i.e., high accuracy measurements of the K-shell transition energies were required for reliably fitting the SXS Perseus spectrum. However, because of the high quality Perseus spectrum, uncertainties in x-ray line strengths, even those on the 10% level or better, are limiting. Here we propose high accuracy measurements of line emission from helium-like ions of astrophysically relevant ions. The measurements will be made using the Lawrence Livermore National Laboratory's electron beam ion trap EBIT-I coupled with high resolution calorimeter spectrometer built at NASA/GSFC and high resolution crystal spectrometers built at LLNL. These measurements will be made at monoenergetic electron impact energies and also as a function of Maxwellian electron temperature using the EBIT Maxwellian simulator. Particular emphasis will be made on the strength of the forbidden line and in experimentally accounting for polarization effects. These data are particularly important for interpretation of high resolution measurements of a plethora of new sources by the calorimeter instrument to be flown on the X-ray Astrophysics Recovery Mission (XARM), as well as the X-IFU spectrometer to be flown on ATHENA.
- Publication:
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NASA APRA Proposal
- Pub Date:
- 2016
- Bibcode:
- 2016apra.prop..102B