XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Highly ionized iron absorption structures

Abstract We present the first high-resolution X-ray spectral analysis of Cygnus X-1 using XRISM. The observation wa3s carried out from 2024 April 7 to 10, covering the orbital phase range 0.65–0.17 during its low/hard state. Taking advantage of the exceptional energy resolution of the Resolve instrument, we examined highly ionized iron absorption lines and characterized the ionization states, column densities, and line-of-sight velocities of the absorbing plasma. Spectral analysis revealed an ionization parameter of $\xi \sim 3$, column densities of a few $\times 10^{21}$ cm$^{-2}$, and a blueshifted velocity of $\sim$100 km s$^{-1}$. The observation was divided into two phases: before and after orbital phase $\phi _{\rm {orb}} = 0.9$, corresponding to non-dipping and dipping intervals. While only weak absorption features were present before $\phi _{\rm {orb}} = 0.9$, strong absorption by He-like and H-like Fe appeared during the dipping phase. We measured equivalent widths of 2.3, 0.4, and 1.2 eV for He-like Fe K$\alpha$ and H-like Ly$\alpha _1$ and Ly$\alpha _2$, respectively—demonstrating the capability of XRISM Resolve to securely detect narrow absorption features of only a few eV. These measurements trace the motion of the absorbing material and offer insight into the kinematics and spatial distribution of the wind in the vicinity of the black hole. These findings enhance our understanding of wind-fed accretion in Cygnus X-1 and highlight the importance of continued high-resolution X-ray observations to further constrain the physical properties of winds and accretion flows in high-mass X-ray binaries.

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Journal
Publications of the Astronomical Society of Japan
Published
2025-09-04
DOI
https://doi.org/10.1093/pasj/psaf104
Citations
1
Primary Topic
Astrophysical Phenomena and Observations
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article
Field-Weighted Citation Impact
1.15

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XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Highly ionized iron absorption structures

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1 citations
Publications of the Astronomical Society of Japan
Astrophysical Phenomena and Observations
1.15
article

XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Highly ionized iron absorption structures

Aya Kubota, Oluwashina Adegoke, Takayoshi Kohmura, J. M. Mïller, Javier A. García, Edmund Hodges‐Kluck, Shōgo Kobayashi, K. Yamaoka, M. C. Brumback, Tsunefumi Mizuno, Ken Ebisawa, Natalie Hell, Misaki Mizumoto, Shunji Kitamoto, E. Costantini, H. Takahashi, S. Yamada, Yuusuke Uchida, Paul A. Draghis, Sixuan Zhang, Kaito Ninoyu
article en
1 citations

Abstract

Abstract We present the first high-resolution X-ray spectral analysis of Cygnus X-1 using XRISM. The observation wa3s carried out from 2024 April 7 to 10, covering the orbital phase range 0.65–0.17 during its low/hard state. Taking advantage of the exceptional energy resolution of the Resolve instrument, we examined highly ionized iron absorption lines and characterized the ionization states, column densities, and line-of-sight velocities of the absorbing plasma. Spectral analysis revealed an ionization parameter of $\xi \sim 3$, column densities of a few $\times 10^{21}$ cm$^{-2}$, and a blueshifted velocity of $\sim$100 km s$^{-1}$. The observation was divided into two phases: before and after orbital phase $\phi _{\rm {orb}} = 0.9$, corresponding to non-dipping and dipping intervals. While only weak absorption features were present before $\phi _{\rm {orb}} = 0.9$, strong absorption by He-like and H-like Fe appeared during the dipping phase. We measured equivalent widths of 2.3, 0.4, and 1.2 eV for He-like Fe K$\alpha$ and H-like Ly$\alpha _1$ and Ly$\alpha _2$, respectively—demonstrating the capability of XRISM Resolve to securely detect narrow absorption features of only a few eV. These measurements trace the motion of the absorbing material and offer insight into the kinematics and spatial distribution of the wind in the vicinity of the black hole. These findings enhance our understanding of wind-fed accretion in Cygnus X-1 and highlight the importance of continued high-resolution X-ray observations to further constrain the physical properties of winds and accretion flows in high-mass X-ray binaries.

Publications of the Astronomical Society of JapanVol. 77(6)
Hiroshima University (JP), California Institute of Technology (US), Lawrence Livermore National Laboratory (US), Goddard Space Flight Center (US), Rikkyo University (JP), Tokyo University of Science (JP), Shibaura Institute of Technology (JP), University of Michigan (US), University of Teacher Education Fukuoka (JP), Japan Aerospace Exploration Agency (JP), Institute of Space and Astronautical Science (JP), Space Research Organisation Netherlands (NL), Nagoya University (JP), Massachusetts Institute of Technology (US)
U.S. Department of Energy, Japan Society for the Promotion of Science, Lawrence Livermore National Laboratory
Openalex Percentile: Top 16%
Astrophysical Phenomena and Observations
1.15
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