Plasma environment effects on K lines of astrophysical interest

II. Ionization potentials, K thresholds, radiative rates, and Auger widths in Ne- through He-like iron ions (Fe XVII – Fe XXV)^⋆

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, USA
⁸ IPNAS, Université de Liège, Sart Tilman 4000 Liège, Belgium
e-mail: Pascal.Quinet@umons.ac.be

Received: 11 March 2019
Accepted: 4 May 2019

Abstract

Aims. In the context of accretion disks around black holes, we estimate plasma-environment effects on the atomic parameters associated with the decay of K-vacancy states in highly charged iron ions, namely Fe XVII – Fe XXV.

Methods. Within the relativistic multiconfiguration Dirac–Fock (MCDF) framework, the electron–nucleus and electron–electron plasma screenings were approximated with a time-averaged Debye–Hückel potential.

Results. Modified ionization potentials, K thresholds, wavelengths, radiative emission rates, and Auger widths are reported for astrophysical plasmas characterized by electron temperatures and densities in the ranges 10⁵ − 10⁷ K and 10¹⁸ − 10²² cm⁻³, respectively.

Conclusions. We conclude that the high-resolution microcalorimeters on board future X-ray missions such as XRISM and ATHENA are expected to be sensitive to the lowering of the iron K edge due to the extreme plasma conditions occurring in accretion disks around compact objects.