Fe XVIII–XXIV Kβ Inner-Shell Absorption Lines in the X-Ray Spectra of Neutron Star and Black Hole Binaries with XRISM

Authors

• Masahiro Tsujimoto, JAXA, ISASFollow
• Daiki Miura, JAXA, ISAS
• Hiroya Yamaguchi, JAXA, ISAS
• Ehud Behar, Technion
• Chris Done, Durham University
• María Díaz Trigo, ESO
• Chamani M. Gunasekera, STSci
• Peter A. M. van Hoof, Royal Observatory of Belgium
• Stefano Bianchi, Università degli Studi Roma Tre
• Maryam Dehghanian, University of KentuckyFollow
• Gary J. Ferland, University of KentuckyFollow

Abstract

The advent of the X-ray microcalorimeter spectrometer Resolve onboard the XRISM space telescope opened a new era for high-resolution X-ray spectroscopy of astrophysical plasmas. Many spectral features were newly detected, including the Kα and Kβ inner-shell transition lines of mildly ionized (F- to Li-like) Fe at 6–8 keV in the spectra of X-ray binaries and active galactic nuclei. The widely used atomic databases contain information on the Kα but not Kβ lines of these ions. We conducted the atomic structure calculation using FAC to derive the Fe Kα and Kβ lines and verified the result against ground experiments and other calculations of the Fe Kα lines. We then implemented the Fe Kβ lines in a radiative transfer code (Cloudy) and compared the synthesized and observed spectra with XRISM. A reasonably good agreement was obtained between the observation and the ab initio calculations. This exemplifies the need to expand the atomic databases to interpret astrophysical spectra.

Document Type

Article

Publication Date

2026

Notes/Citation Information

© 2026 The Japan Society of Plasma Science and Nuclear Fusion Research

Digital Object Identifier (DOI)

https://doi.org/10.1585/pfr.21.2401002

Funding Information

This work was supported by the JSPS Core-to-Core Program (grant number: JPJSCCA20220002) and made use of the JAXA’s high- performance computing system JSS3.

Repository Citation

Tsujimoto, Masahiro; Miura, Daiki; Yamaguchi, Hiroya; Behar, Ehud; Done, Chris; Trigo, María Díaz; Gunasekera, Chamani M.; van Hoof, Peter A. M.; Bianchi, Stefano; Dehghanian, Maryam; and Ferland, Gary J., "Fe XVIII–XXIV Kβ Inner-Shell Absorption Lines in the X-Ray Spectra of Neutron Star and Black Hole Binaries with XRISM" (2026). Physics and Astronomy Faculty Publications. 766.
https://uknowledge.uky.edu/physastron_facpub/766