X-ray spectra of the Fe-L complex

II. Atomic data constraints from the EBIT experiment and X-ray grating observations of Capella

¹ RIKEN High Energy Astrophysics Laboratory, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
e-mail: l.gu@sron.nl
² SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
³ NASA/Goddard Space Flight Center, 8800 Greenbelt Rd, Greenbelt, MD 20771, USA
⁴ Max-Planck-Institut für Kernphysik, Heidelberg 69117, Germany
⁵ Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK
⁶ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
⁷ INAF – IASF Palermo, Via U. La Malfa 153, 90146 Palermo, PA, Italy
⁸ MTA-Eötvös University Lendület Hot Universe Research Group, Pázmány Péter sétány 1/A, Budapest 1117, Hungary
⁹ Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotláská 2, Brno 611 37, Czech Republic
¹⁰ School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
¹¹ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
¹² Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa 277-8583, Japan
¹³ ESTEC/ESA, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹⁴ Laboratory of Instrumentation, Biomedical Engineering and Radiation Physics (LIBPhys-UNL), Department of Physics, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
¹⁵ Space Science Laboratory, University of California, Berkeley, CA 94720, USA

Received: 13 March 2020
Accepted: 8 July 2020

Abstract

The Hitomi results for the Perseus cluster have shown that accurate atomic models are essential to the success of X-ray spectroscopic missions and just as important as the store of knowledge on instrumental calibration and astrophysical modeling. Preparing the models requires a multifaceted approach, including theoretical calculations, laboratory measurements, and calibration using real observations. In a previous paper, we presented a calculation of the electron impact cross sections on the transitions forming the Fe-L complex. In the present work, we systematically tested the calculation against cross-sections of ions measured in an electron beam ion trap experiment. A two-dimensional analysis in the electron beam energies and X-ray photon energies was utilized to disentangle radiative channels following dielectronic recombination, direct electron-impact excitation, and resonant excitation processes in the experimental data. The data calibrated through laboratory measurements were further fed into a global modeling of the Chandra grating spectrum of Capella. We investigated and compared the fit quality, as well as the sensitivity of the derived physical parameters to the underlying atomic data and the astrophysical plasma modeling. We further list the potential areas of disagreement between the observations and the present calculations, which, in turn, calls for renewed efforts with regard to theoretical calculations and targeted laboratory measurements.