High resolution x-RAY spectra obtained with the micro-calorimeter onboard hitomi have demonstrated the diagnostic powers of k-shell transitions of a wide range of astrophysically abundant ions. The…

The Regents of the University of California, doing business as University of California, Berkeley, has been awarded a $251,123 grant by the National Aeronautics and Space Administration Shared Services Center to conduct theoretical atomic physics research. Specifically, UC Berkeley will use the Flexible Atomic Code to calculate accurate atomic structure and collisional-radiative data for ions of carbon through zinc relevant for high-resolution x-ray spectroscopy observations from NASA's upcoming XRISM and Athena observatories. The research aims to produce spectroscopic data for modeling astrophysical plasma with an accuracy of better than 0.1 eV for transition energies, 5% for radiative decay rates, and 10% for relatively strong line emissivities. The grant does not utilize a small business set-aside and is scheduled to complete by March 2024. As the parent organization, the State of California Controllers Office would administer any funding provided to UC Berkeley under this research grant.

High resolution x-RAY spectra obtained with the micro-calorimeter onboard hitomi have demonstrated the diagnostic powers of k-shell transitions of a wide range of astrophysically abundant ions. The analyses of these spectra have also exposed various limitations of atomic data employed in the state-of-the-art plasma modeling codes, such as atomdb/apec, spex, and chianti. Chief among the problems are: a) different codes exhibit significant variation in spontaneous decay rates of strong transitions in he-like like ions up to 30% b) similar or even larger discrepancies in the effective collision strength of forbidden transitions of h-like and he-like ions c) incomplete, inaccurate line energies and emissivities of satellite transitions of lower charge states resulting from dielectronic recombination, innershell excitation and ionization. These problems cause significant bias on the derived plasma parameters of various astrophysical sources. Here we propose a systematic theoretical study of all k-shell atomic data relevant for high resolution x-RAY data expected from xrism and athena observatories, with the aim of producing a complete collisional radiative dataset with spectroscopic accuracy for ions of carbon to zinc, meaning achieving accuracy of better than 0.1 EV in transition energies, better than 5% in radiative decay rates, and better than 10% in line emissivities for relatively strong transitions. The flexible atomic code (FAC) developed and maintained by the principle investigator will be used for this study. The combined configuration interaction and many body perturbation theory (mbpt) method implemented in FAC has been shown to be capable of achieving desired accuracy on transition energies and radiative decay rates. We will apply this method to both bound and autoionizing states to obtain accurate structure data for both main and satellite transitions. The collisional processes will be calculated by the distorted-wave (DW) and dirac r-matrix modules implemented in FAC. The PI has recently developed methods to include mbpt corrections in the DW module, and has demonstrated its high accuracy in treating even more complex ions such as NE-like iron. A similar mbpt correction option will be developed for the r-matrix module during the course of this investigation.