Plasma-environment effects on K lines of astrophysical interest

III. IPs, K thresholds, radiative rates, and Auger widths in Fe IX – Fe XVI^⋆

¹ Physique Atomique et Astrophysique, Université de Mons – UMONS, 7000 Mons, Belgium
e-mail: patrick.palmeri@umons.ac.be
² Department of Physics, Western Michigan University, Kalamazoo, MI 49008, USA
³ Helmholtz Institut Jena, 07743 Jena, Germany
⁴ Theoretisch Physikalisches Institut, Friedrich Schiller Universität Jena, 07743 Jena, Germany
⁵ Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
⁶ Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics, Sternwartstr. 7, 96049 Bamberg, Germany
⁷ NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA
⁸ IPNAS, Université de Liège, Sart Tilman, 4000 Liège, Belgium

Received: 8 November 2019
Accepted: 29 January 2020

Abstract

Aims. In the context of black-hole accretion disks, we aim to compute the plasma-environment effects on the atomic parameters used to model the decay of K-vacancy states in moderately charged iron ions, namely Fe IX – Fe XVI.

Methods. We used the fully relativistic multiconfiguration Dirac–Fock method approximating the plasma electron–nucleus and electron–electron screenings with a time-averaged Debye–Hückel potential.

Results. We report modified ionization potentials, K-threshold energies, wavelengths, radiative emission rates, and Auger widths for plasmas characterized by electron temperatures and densities in the ranges 10⁵−10⁷ K and 10¹⁸−10²² cm⁻³.

Conclusions. This study confirms that the high-resolution X-ray spectrometers onboard the future XRISM and Athena space missions will be capable of detecting the lowering of the K edges of these ions due to the extreme plasma conditions occurring in accretion disks around compact objects.