Spectroscopic diagnostics of high-temperature plasma in stellar coronae using Fe <scp>xxiv</scp>–<scp>xxiv</scp> K-shell lines with XRISM
Abstract The RS CVn type binary star GT Muscae was observed during its quiescence using the Resolve X-ray microcalorimeter spectrometer onboard XRISM. The main and satellite lines of the Fe xxiv–xxiv K-shell transitions were resolved for the first time from stellar sources. We conducted line ratio analysis to investigate any deviations from collisional ionization equilibrium and Maxwell electron energy distribution with a single temperature. By using five combinations of direct excitation lines and dielectronic recombination satellite lines in three line complexes (Fe He$\alpha$, Ly$\alpha$, and He$\beta$), we found that the plasma is well characterized by two-temperature thermal plasmas with temperatures of 1.7 and 4.3 keV, which is consistent with thermal broadening of Fe xxv, and the broad-band fitting results in the 1.7–10 keV band. Other forms of deviation from a single-temperature plasma, such as different ionization and electron temperatures or the $\kappa$ distribution for the electron energy distributions, are not favored, which is reasonable for stellar coronae at quiescence. This study demonstrates the utility of the Fe K-shell line ratio diagnostics to probe plasma conditions using X-ray microcalorimeters.
Authors
- Ehud Behar (ORCID: https://orcid.org/0000-0001-9735-4873)
- M. Audard (ORCID: https://orcid.org/0000-0003-4721-034X)
- Kenji Hamaguchi (ORCID: https://orcid.org/0000-0001-7515-2779)
- Masahiro Tsujimoto (ORCID: https://orcid.org/0000-0002-9184-5556)
- Yoshitomo Maeda (ORCID: https://orcid.org/0000-0002-9099-5755)
- Liyi Gu (ORCID: https://orcid.org/0000-0001-9911-7038)
- Miki Kurihara
- Natalie Hell (ORCID: https://orcid.org/0000-0003-3057-1536)
- Caroline A. Kilbourne (ORCID: https://orcid.org/0000-0001-9464-4103)
- Y. Tsuboi (ORCID: https://orcid.org/0000-0001-9943-0024)
- Frederick S Porter
- H. Sugai
Institutions
- University of Geneva (CH)
- Lawrence Livermore National Laboratory (US)
- Goddard Space Flight Center (US)
- Technion – Israel Institute of Technology (IL)
- Japan Aerospace Exploration Agency (JP)
- Institute of Space and Astronautical Science (JP)
- Space Research Organisation Netherlands (NL)
- The University of Tokyo (JP)
- University of Maryland, Baltimore County (US)
- Chuo University (JP)
Publication Details
- Journal
- Publications of the Astronomical Society of Japan
- Published
- 2025-06-03
- DOI
- https://doi.org/10.1093/pasj/psaf045
- Citations
- 4
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 4.62
Funders
- U.S. Department of Energy
- National Aeronautics and Space Administration
- George Mason University
- University of Michigan
- University of Cambridge
- National Astronomical Observatory of Japan
- Goddard Space Flight Center
- National Institutes of Natural Sciences
- Lawrence Livermore National Laboratory