High-resolution wavelength measurements of Mn and Cr K-shell lines for x-ray astrophysics

X-ray spectrometers and telescopes in space are currently capable of detecting weak spectral lines of trace elements such as manganese (Mn) and chromium (Cr). For example, Kα emission lines from Cr and Mn have been observed in the X-ray spectra of supernova remnants, including W49B, Tycho, Kepler, and Cas A. XRISM/Resolve will be able to resolve individual lines of these ions, as was demonstrated by the observation of the Perseus cluster using the very similar Hitomi/SXS. The Mn-to-Cr mass ratio can be calculated from the line flux ratio and specific emissivities and provides a means of measuring directly the metallicity of the progenitor star. However, the accuracy of the underlying atomic data often dominates the uncertainties in the derived metallicities. As a first step toward improving the available atomic data, we have measured the line centers for K-shell transitions in Mn XVII-XXIII and Cr XVI-XXII ions at high spectral resolution. The measurements were done with the Electron Beam Ion Trap (EBIT) Calorimeter Spectrometer - a calorimeter comparable to Hitomi-SXS and XRISM-Resolve - at the Lawrence Livermore National Laboratory EBIT-I.

Part of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and is also supported by NASA grants to LLNL, NASA/GSFC, and Columbia University.