arxiv: 2604.21497 · v1 · submitted 2026-04-23 · 🌌 astro-ph.HE

Recognition: unknown

XRISM High-Resolution X-ray Spectroscopy of Cygnus X-1 -- highly ionized Iron absorption structures

Shinya Yamada , Natalie Hell , Elisa Costantini , Oluwashina Adegoke , McKinley Brumback , Paul Draghis , Ken Ebisawa , Javier A. Garcia

show 13 more authors

Edmund Hodges-Kluck Shunji Kitamoto Shogo Kobayashi Takayoshi Kohmura Aya Kubota Jon M. Miller Misaki Mizumoto Tsunefumi Mizuno Kaito Ninoyu Hiromitsu Takahashi Yuusuke Uchida Kazutaka Yamaoka Sixuan Zhang

Authors on Pith no claims yet

Pith reviewed 2026-05-09 21:18 UTC · model grok-4.3

classification 🌌 astro-ph.HE

keywords Cygnus X-1XRISMiron absorptionphotoionized windX-ray binariesblack hole accretionhigh-resolution spectroscopydipping phase

0 comments

The pith

XRISM Resolve detects narrow highly ionized iron absorption lines in Cygnus X-1 with blueshift of 100 km/s and ionization parameter near 3.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper presents the first high-resolution X-ray spectra of Cygnus X-1 taken with XRISM Resolve during its low/hard state, covering orbital phases that include both non-dipping and dipping intervals. Analysis of the iron K region shows that absorption lines from He-like and H-like iron strengthen markedly after orbital phase 0.9, yielding equivalent widths of 2.3 eV, 0.4 eV, and 1.2 eV and allowing derivation of an ionization parameter of approximately 3, column densities of a few times 10^21 cm^-2, and a blueshifted velocity of approximately 100 km s^-1. A sympathetic reader would care because these quantities directly constrain the velocity field and spatial structure of the accretion wind in a wind-fed black-hole binary.

Core claim

The central claim is that XRISM Resolve can securely detect narrow absorption features only a few eV wide in Cygnus X-1, revealing a photoionized plasma absorber whose properties are an ionization parameter of approximately 3, column densities of a few times 10^21 cm^-2, and a line-of-sight blueshift of approximately 100 km s^-1, with the absorption becoming prominent during the dipping orbital phase.

What carries the argument

The photoionized plasma absorption model fitted to the resolved He-like Fe K-alpha and H-like Fe Ly-alpha lines, which simultaneously returns the ionization parameter, column density, and Doppler velocity of the wind material.

If this is right

The absorbing plasma is spatially distributed such that its column becomes detectable only during the dipping phase.
The measured 100 km s^-1 blueshift traces the line-of-sight motion of wind material in the vicinity of the black hole.
The derived ionization parameter and column density constrain the physical conditions in the wind that feeds the accretion flow.
Continued high-resolution observations can further map how the wind kinematics vary with orbital phase.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The phase-dependent strength suggests the wind is clumpy or focused along certain sightlines through the binary.
The same Resolve capabilities could be used on other high-mass X-ray binaries to compare wind launching radii and velocities across systems.
If the velocity remains stable in future epochs, the absorber may originate from a fixed region such as the companion's wind or the disk atmosphere.

Load-bearing premise

The spectral fitting assumes the absorption arises from a uniform photoionized plasma component whose properties can be captured by a single ionization parameter and column density, with the orbital phase cut at phi_orb=0.9 cleanly separating dipping and non-dipping intervals without significant continuum or instrumental contamination.

What would settle it

A repeat high-resolution observation that fails to detect absorption lines with equivalent widths near 2.3 eV, 0.4 eV, and 1.2 eV or that measures a velocity shift significantly different from 100 km s^-1 during the dipping phase would falsify the reported plasma properties.

Figures

Figures reproduced from arXiv: 2604.21497 by Aya Kubota, Edmund Hodges-Kluck, Elisa Costantini, Hiromitsu Takahashi, Javier A. Garcia, Jon M. Miller, Kaito Ninoyu, Kazutaka Yamaoka, Ken Ebisawa, McKinley Brumback, Misaki Mizumoto, Natalie Hell, Oluwashina Adegoke, Paul Draghis, Shinya Yamada, Shogo Kobayashi, Shunji Kitamoto, Sixuan Zhang, Takayoshi Kohmura, Tsunefumi Mizuno, Yuusuke Uchida.

**Figure 1.** Figure 1: Light curves of XRISM and Xtend. The light curve constructed from the entire energy band of Resolve, using only Hp events and all pixels except for the calibration pixel (black), covering approximately 1.6–25 keV. The Xtend light curves are obtained in two energy bands: 0.5–3 keV (red) and 3–10 keV (blue). The x-axis indicates the elapsed time since the beginning of the observation, and the y-axis shows th… view at source ↗

**Figure 2.** Figure 2: Observed spectra of Cyg X-1 in the 4–10 keV range from Resolve and Xtend. Both spectra include the effects of detector response. The shape of the Resolve spectrum is primarily influenced by absorption through the beryllium window in the gate valve. The vertical axis of the Xtend spectrum is scaled down by a factor of 12. The inset in the upper right corner provides a close-up view of the Resolve spectrum i… view at source ↗

**Figure 3.** Figure 3: Time-averaged Resolve spectrum and the best-fit model, with enlarged views highlighting the He-like and H-like Fe Kα and Kβ series. (Top) Measured photon count spectrum without any correction for effective area and the best-fit model over 6.5–10 keV. (Bottom) A close-up view at around Fe Kα (left) and Fe Kβ (right). For each panel, residuals between the data and the model are shown. The energies of represe… view at source ↗

**Figure 4.** Figure 4: Detailed view of the measurement of turbulent velocity and Doppler shift using the time-averaged spectrum fitted with an ionized absorption model. (Top) Comparison of four representative models applied to the time-averaged spectrum. The solid lines correspond to: (i) z = 0, vturb = 0 (blue), (ii) z = 0, vturb free (green-yellow), (iii)z free, vturb = 0 (yellow), and (iv) z free, vturb free (cyan). (Bottom)… view at source ↗

**Figure 5.** Figure 5: (Top) The measured photon count spectra divided at ϕorb = 0.9. The data during dipping intervals are shown in light blue, while the non-dip spectrum are shown in black. The best-fit models (solid yellow lines) and the power-law continuum (solid green line) fitted to the 4–10 keV spectrum of Cyg X-1 are overlaid. (Middle) Ratios of the spectra to the powerlaw model (green solid in the top panel). (Bottom) R… view at source ↗

**Figure 6.** Figure 6: (Top) Visualization of the projected velocity along the LOS toward the BH, assuming a spherically symmetric stellar wind. The inset in the lower right illustrates a conceptual diagram, where the viewing angle is defined as 0 degrees when the observer looks perpendicular to the line connecting the star and the BH. Velocity vectors are defined as positive in the direction toward the BH (shown as blue arrows)… view at source ↗

**Figure 7.** Figure 7: Results of the photoionization calculations using Cloudy for the BH low/hard state SED. The horizontal axis represents the ionization parameter log ξ. Top panel: Fractional abundances of iron ions (Fe, Fe+, ..., Fe25+) as a function of log ξ. Bottom panel: Electron temperature as a function of log ξ. At log ξ > ∼ 3, iron is nearly fully ionized, and the electron temperature exceeds 107 K. Alt text: logξ v… view at source ↗

**Figure 9.** Figure 9: Spectrum of Fe-55 isotopes obtained during the observation of Cyg X-1, summed over all pixels except the calibration pixel, is shown together with the best-fit model. For the theoretical modeling of Mn Kα, the total model is shown in red, while the eight constituent Voigt profiles are displayed in different colors. The lower panel shows the residuals between the data and the model. Alt text: Energy vs. cou… view at source ↗

**Figure 10.** Figure 10: Evaluation of energy resolution (top) and energy centroid (bottom) using the Mn Kα line from Fe-55 isotopes. Results are shown in pink and light blue for ϕorb < 0.9 and ϕorb ≥ 0.9, respectively; yellow indicates the entire observation, and black shows the result from data reprocessed with rslgain. In both panels, the position at pixel −1 indicates the fit result obtained by summing over all pixels except… view at source ↗

read the original abstract

We present the first high-resolution X-ray spectral analysis of Cygnus X-1 using XRISM. The observation was carried out from April 7 to 10, 2024, 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 approximately 3, column densities of a few times 10^21 cm^-2, and a blueshifted velocity of approximately 100 km s^-1. The observation was divided into two phases: before and after orbital phase phi_orb = 0.9, corresponding to non-dipping and dipping intervals. While only weak absorption features were present before phi_orb = 0.9, strong absorption by He-like and H-like Fe appeared during the dipping phase. We measured equivalent widths of 2.3 eV, 0.4 eV, and 1.2 eV for He-like Fe K-alpha, and H-like Ly-alpha1 and Ly-alpha2, 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.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This is the first XRISM Resolve spectrum of Cygnus X-1, delivering clean detections of narrow Fe absorption lines that strengthen in the dipping phase, but the single-zone photoionized model leaves the physical picture incomplete.

read the letter

The main takeaway is straightforward: this is the first published XRISM Resolve observation of Cygnus X-1, and it shows clear, narrow absorption from highly ionized iron that is much stronger after orbital phase 0.9. The authors report equivalent widths of 2.3 eV for the He-like K-alpha line and 0.4 plus 1.2 eV for the two H-like Ly-alpha components, along with a fitted ionization parameter around 3, column density of a few times 10^21 cm^-2, and a line-of-sight blueshift near 100 km/s. That is genuinely new data from a new instrument, and the numbers are tied directly to the spectra rather than derived from some circular argument. The work also shows that Resolve can securely measure features only a few eV wide, which is useful for anyone planning similar observations of winds in high-mass X-ray binaries. The phase split at 0.9 cleanly separates the weak and strong absorption intervals, and the abstract gives concrete measured values without obvious over-claiming. The soft spot is the modeling choice. The analysis assumes a single uniform photoionized plasma component to explain the lines. In the dipping phase the absorber is likely clumpy or multi-phase with possible velocity gradients, so the reported parameters are effective averages whose direct physical meaning for the wind structure is limited. The paper does not appear to test multi-zone models or quantify how much the results change if the uniformity assumption is relaxed. That does not invalidate the detections, but it caps how far the numbers can be pushed. This paper is for people who follow X-ray binary winds and high-resolution spectroscopy. It adds a solid new data point without reshaping the field. The observations are new and the analysis is transparent enough that it deserves a serious referee rather than a desk reject; the main revisions would be around testing the model assumptions and expanding the error discussion.

Referee Report

2 major / 2 minor

Summary. The manuscript presents the first high-resolution X-ray spectroscopic analysis of Cygnus X-1 using the XRISM Resolve instrument during its low/hard state (orbital phases 0.65--0.17). The data are split at phi_orb=0.9 into non-dipping and dipping intervals. Spectral fitting of highly ionized Fe absorption lines (He-like K-alpha and H-like Ly-alpha) with a photoionized plasma model yields an ionization parameter of approximately 3, column density of a few times 10^21 cm^{-2}, and blueshifted velocity of approximately 100 km s^{-1}. Equivalent widths of 2.3 eV, 0.4 eV, and 1.2 eV are reported for the respective lines, detected primarily in the dipping phase.

Significance. If the modeling assumptions hold, this work demonstrates XRISM Resolve's capability to securely detect narrow absorption features with equivalent widths of only a few eV and provides new phase-resolved constraints on the highly ionized wind in the archetypal black-hole binary Cygnus X-1. It links dipping behavior to enhanced absorption and offers initial kinematic and ionization insights into wind-fed accretion near the compact object.

major comments (2)

[§4] §4 (Spectral Analysis and phase-resolved fitting): The central results (xi≈3, N_H≈few×10^{21} cm^{-2}, v≈100 km s^{-1}) rest on a single-zone photoionized plasma model applied to the dipping interval. The manuscript must show that this model is statistically adequate (e.g., chi^2/dof, residual plots, and line-profile fits) and address whether a multi-zone or clumpy absorber is required, as the dipping material is expected to be inhomogeneous. Without such validation, the reported parameters are effective averages whose physical meaning for the wind remains unclear.
[Results] Results section (equivalent-width measurements): The quoted equivalent widths (2.3 eV, 0.4 eV, 1.2 eV) are presented without uncertainties or detection significances. These must be included, together with the continuum-subtraction method and atomic data source, to substantiate the claim of secure detection of narrow features.

minor comments (2)

The abstract and introduction would benefit from explicit reference to the energy band and specific transitions used in the line fitting.
A summary table of best-fit parameters (with 1-sigma errors) for both orbital-phase intervals would improve clarity and allow direct comparison with prior lower-resolution studies.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and valuable comments, which have helped us improve the clarity and robustness of our analysis. We provide point-by-point responses below and will make the necessary revisions to the manuscript.

read point-by-point responses

Referee: [§4] §4 (Spectral Analysis and phase-resolved fitting): The central results (xi≈3, N_H≈few×10^{21} cm^{-2}, v≈100 km s^{-1}) rest on a single-zone photoionized plasma model applied to the dipping interval. The manuscript must show that this model is statistically adequate (e.g., chi^2/dof, residual plots, and line-profile fits) and address whether a multi-zone or clumpy absorber is required, as the dipping material is expected to be inhomogeneous. Without such validation, the reported parameters are effective averages whose physical meaning for the wind remains unclear.

Authors: We agree that additional validation of the single-zone photoionized plasma model is necessary to support our conclusions. In the revised manuscript, we will include the chi^2/dof values for the spectral fits to the dipping interval, along with residual plots and detailed line-profile fits showing the model components. We will also explicitly address the potential need for multi-zone or clumpy absorbers by discussing the expected inhomogeneity of the dipping material and noting that our reported parameters represent effective averages over the line of sight. We will test whether adding a second absorption zone significantly improves the fit statistics and include this in the revised analysis section. This will clarify the physical interpretation of the wind properties. revision: yes
Referee: [Results] Results section (equivalent-width measurements): The quoted equivalent widths (2.3 eV, 0.4 eV, 1.2 eV) are presented without uncertainties or detection significances. These must be included, together with the continuum-subtraction method and atomic data source, to substantiate the claim of secure detection of narrow features.

Authors: We thank the referee for pointing out this omission. In the revised manuscript, we will report the equivalent widths with their uncertainties and include the detection significances (e.g., in terms of sigma). We will describe the continuum-subtraction method employed, which involves fitting a local power-law or spline continuum around each absorption line, and specify the atomic data source used in the photoionization modeling. These additions will strengthen the evidence for the secure detection of the narrow features with XRISM Resolve. revision: yes

Circularity Check

0 steps flagged

No circularity: parameters are direct spectral-fit outputs

full rationale

The paper performs standard X-ray spectral fitting of Resolve data using conventional photoionized plasma models (e.g., single-zone absorption components) on observed line positions and strengths. The reported ionization parameter (≈3), column density (few × 10^21 cm^-2), blueshift (≈100 km s^-1), and equivalent widths are direct numerical outputs of that fitting process applied to the data split at phi_orb=0.9. No equations, self-citations, or ansatzes reduce these quantities to quantities defined by the fit itself; the central results remain independent empirical measurements rather than tautological re-expressions of inputs.

Axiom & Free-Parameter Ledger

3 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard X-ray spectral modeling of photoionized winds and the known orbital behavior of Cygnus X-1; no new entities are postulated.

free parameters (3)

ionization parameter = ~3
Fitted value (~3) that sets the ionization balance of the absorbing plasma to match observed line ratios.
column density = few x 10^21 cm^-2
Fitted hydrogen column (~few x 10^21 cm^-2) that scales the optical depth of the absorption lines.
line-of-sight velocity = ~100 km/s
Fitted blueshift (~100 km/s) derived from the observed line centroid shifts.

axioms (2)

domain assumption The detected features are absorption lines from He-like and H-like iron in a photoionized plasma.
Standard assumption in X-ray spectroscopy of accretion winds; invoked when assigning the observed lines to specific ions.
domain assumption Orbital phase phi_orb = 0.9 cleanly divides intervals with distinct absorption properties.
Based on prior knowledge of dipping behavior in Cygnus X-1; used to split the dataset.

pith-pipeline@v0.9.0 · 5719 in / 1586 out tokens · 41851 ms · 2026-05-09T21:18:00.956023+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

94 extracted references

[1]

D., Acernese, F., et al

Abbott, R., Abbott, T. D., Acernese, F., et al. 2023, Phys. Rev. X, 13, 011048,

2023
[2]

2018, Monthly Notices of the Royal Astronomical Society, 480, 751,

Axelsson, M., & Done, C. 2018, Monthly Notices of the Royal Astronomical Society, 480, 751,

2018
[3]

J., Charles, P

Balucinska-Church, M., Church, M. J., Charles, P . A., et al. 2000, Mon. Not. R. Astron. Soc., 311, 861,

2000
[4]

2022, in Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, ed

Boissay-Malaquin, R., Hayashi, T., Tamura, K., et al. 2022, in Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, ed. J.-W. A. den Herder, K. Nakazawa, & S. Nikzad (SPIE),

2022
[5]

2024, in Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, ed

Boissay-Malaquin, R., Hayashi, T., Tamura, K., et al. 2024, in Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, ed. J.-W. A. den Herder, K. Nakazawa, & S. Nikzad (SPIE), 237,

2024
[6]

1952, Mon

Bondi, H. 1952, Mon. Not. R. Astron. Soc., 112, 195,

1952
[7]

1944, Mon

Bondi, H., & Hoyle, F. 1944, Mon. Not. R. Astron. Soc., 104, 273,

1944
[8]

Boroson, B., & Vrtilek, S. D. 2010, Astrophys. J., 710, 197,

2010
[9]

P ., Larionov, V ., et al

Brocksopp, C., Fender, R. P ., Larionov, V ., et al. 1999, Mon. Not. R. Astron. Soc., 309, 1063,

1999
[10]

I., Abbott, D

Castor, J. I., Abbott, D. C., & Klein, R. I. 1975, Astrophys. J., 195, 157,

1975
[11]

2015, Astron

Cechura, P ., & Hadrava, P . 2015, Astron. Astrophys., 575, A5,

2015
[12]

2007, Astrophys

Chang, C., & Cui, W. 2007, Astrophys. J., 663, 1207,

2007
[13]

2023, Rev

Chatzikos, M., Bianchi, S., Camilloni, F., et al. 2023, Rev. Mex. Astron. Astroﬁs., 59, 327, de Vries, C. P ., Haas, D., Y amasaki, N. Y ., et al. 2017, JA TIS, 4, 011204,

2023
[14]

Dexter, J., & Begelman, M. C. 2023, Mon. Not. R. Aston. Soc. Lett., 528, L157,

2023
[15]

2007, The Astronomy and Astrophysics Review, 15, 1,

Done, C., Gierli ´nski, M., & Kubota, A. 2007, The Astronomy and Astrophysics Review, 15, 1,

2007
[16]

A., Miller, J

Draghis, P . A., Miller, J. M., Costantini, E., et al. 2024, Astrophys. J., 969, 40,

2024
[17]

E., Adams, J

Eckart, M. E., Adams, J. S., Boyce, K. R., et al. 2018, J. Astron. Telesc. Instrum. Syst., 4, 1,

2018
[18]

E., Brown, G

Eckart, M. E., Brown, G. V ., Chiao, M. P ., et al. 2025b, Journal of Astronomical Telescopes, Instruments, and Systems, 11, 042018, El Mellah, I., Grinberg, V ., Sundqvist, J. O., Driessen, F. A., & Leutenegger, M. A. 2020, Astron. Astrophys., 643, A9,

2020
[19]

X., Tennant, A

Feng, Y . X., Tennant, A. F., & Zhang, S. N. 2003, The Astrophysical Journal, 597, 1017,

2003
[20]

B., & Castor, J

Friend, D. B., & Castor, J. I. 1982, Astrophys. J., 261, 293,

1982
[21]

R., & Bolton, C

Gies, D. R., & Bolton, C. T. 1986, Astrophys. J., 304, 371, 14 Publications of the Astronomical Society of Japan (0000), Vol. 00, No. 0

1986
[22]

1999, Astronomy and Astrophysics, 352, 182, Gräfener, G., Koesterke, L., & Hamann, W.-R

Gilfanov, M., Churazov, E., & Revnivtsev, M. 1999, Astronomy and Astrophysics, 352, 182, Gräfener, G., Koesterke, L., & Hamann, W.-R. 2002, Astronomy and Astrophysics, 387, 244,

1999
[23]

2013, Astron

Grinberg, V ., Hell, N., Pottschmidt, K., et al. 2013, Astron. Astrophys., 554, A88,

2013
[24]

A., Hell, N., et al

Grinberg, V ., Leutenegger, M. A., Hell, N., et al. 2015, Astron. Astrophys., 576, A117,

2015
[25]

M., van Hoof, P

Gunasekera, C. M., van Hoof, P . A. M., Chatzikos, M., & Ferland, G. J. 2023, Research Notes of the American Astronomical Society, 7, 246,

2023
[26]

A., et al

Hanke, M., Wilms, J., Nowak, M. A., et al. 2009, Astrophys. J., 690, 330,

2009
[27]

2022, in Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, ed

Hayashi, T., Boissay-Malaquin, R., Tamura, K., et al. 2022, in Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, ed. J.-W. A. den Herder, K. Nakazawa, & S. Nikzad (SPIE),

2022
[28]

P ., Gabler, R., Vilchez, J

Herrero, A., Kudritzki, R. P ., Gabler, R., Vilchez, J. M., & Gabler, A. 1995, Astron. Astrophys., 297, 556

1995
[29]

2021, pasa, 38, e056,

Hirai, R., & Mandel, I. 2021, pasa, 38, e056,

2021
[30]

2019, Astron

Hirsch, M., Hell, N., Grinberg, V ., et al. 2019, Astron. Astrophys., 626, A64,

2019
[31]

S., Kaluzienski, L

Holt, S. S., Kaluzienski, L. J., Boldt, E. A., & Serlemitsos, P . J. 1976, Nature, 261, 213, Hölzer, G., Fritsch, M., Deutsch, M., Härtwig, J., & Förster, E. 1997, Phys. Rev. A, 56, 4554,

1976
[32]

2016, Nucl

Inoue, S., Hayashida, K., Katada, S., et al. 2016, Nucl. Instrum. Methods Phys. Res. A, 831, 415,

2016
[33]

2018, JA TIS, 4, 011217,

Ishisaki, Y ., Y amada, S., Seta, H., et al. 2018, JA TIS, 4, 011217,

2018
[34]

L., Awaki, H., et al

Ishisaki, Y ., Kelley, R. L., Awaki, H., et al. 2022, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, V ol. 12181, Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, ed. J.- W. A. den Herder, K. Nakazawa, & S. Nikzad (SPIE), 121811S,

2022
[35]

2001, The Astrophysical Journal Supplement Series, 133, 221,

Kallman, T., & Bautista, M. 2001, The Astrophysical Journal Supplement Series, 133, 221,

2001
[36]

L., Akamatsu, H., Azzarello, P ., et al

Kelley, R. L., Akamatsu, H., Azzarello, P ., et al. 2016, in Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray, ed. J.-W. A. den

2016
[37]

T., et al

Kitamoto, S., Miyamoto, S., Tanaka, Y . T., et al. 1984, Publications of the Astronomical Society of Japan, 36, 731 König, O., Mastroserio, G., Dauser, T., et al. 2024, arXiv [astro-ph.HE]

1984
[38]

2007, Publications of the Astronomical Society of Japan, 59, S23

Koyama, K., Tsunemi, H., Dotani, T., et al. 2007, Publications of the Astronomical Society of Japan, 59, S23

2007
[39]

V ., et al

Kravtsov, V ., V eledina, A., Berdyugin, A. V ., et al. 2023, Astron. Astrophys., 678, A58,

2023
[40]

2022, Science, 378, 650,

Krawczynski, H., Muleri, F., Dov ˇciak, M., et al. 2022, Science, 378, 650,

2022
[41]

A., Holland, S

Krimm, H. A., Holland, S. T., Corbet, R. H. D., et al. 2013, The Astrophysical Journal Supplement, 209, 14,

2013
[42]

V ., De Marco, B., Cavecchi, Y ., et al

Lai, E. V ., De Marco, B., Cavecchi, Y ., et al. 2024, Astron. Astrophys., 691, A78,

2024
[43]

Lamers, H. J. G. L. M., & Leitherer, C. 1993, Astrophys. J., 412, 771,

1993
[44]

A., Gregory, V

Leutenegger, M. A., Gregory, V . B., Chiao, M. P ., et al. 2025, in JA TIS (SPIE)

2025
[45]

2008, Publ

Makishima, K., Takahashi, H., Y amada, S., et al. 2008, Publ. Astron. Soc. Jpn. Nihon Tenmon Gakkai, 60, 585,

2008
[46]

2009, Publ

Matsuoka, M., Kawasaki, K., Ueno, S., et al. 2009, Publ. Astron. Soc. Jpn. Nihon Tenmon Gakkai, 61, 999,

2009
[47]

S., & Kallman, T

Mehdipour, M., Kaastra, J. S., & Kallman, T. 2016, Astron. Astrophys., 596, A65,

2016
[48]

2020, in Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, ed

Midooka, T., Tsujimoto, M., Kitamoto, S., et al. 2020, in Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, ed. J.-W. A. den

2020
[49]

2011, Publ

Mihara, T., Nakajima, M., Sugizaki, M., et al. 2011, Publ. Astron. Soc. Jpn. Nihon Tenmon Gakkai, 63, S623,

2011
[50]

M., Wojdowski, P ., Schulz, N

Miller, J. M., Wojdowski, P ., Schulz, N. S., et al. 2005, Astrophys. J., 620, 398,

2005
[51]

Miller-Jones, J. C. A., Bahramian, A., Orosz, J. A., et al. 2021, Science, 371, 1046, Miškoviˇcová, I., Hell, N., Hanke, M., et al. 2016, Astron. Astrophys., 590, A114,

2021
[52]

1988, Nature, 336, 450,

Miyamoto, S., Kitamoto, S., Mitsuda, K., & Dotani, T. 1988, Nature, 336, 450,

1988
[53]

2025, Publications of the Astronomical Society of Japan, saf071,

Mizumoto, M., Kanemaru, Y ., Y amada, S., et al. 2025, Publications of the Astronomical Society of Japan, saf071,

2025
[54]

2022, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, V ol

Mori, K., Tomida, H., Nakajima, H., et al. 2022, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, V ol. 12181, Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, ed. J.-W. A. den Herder, S. Nikzad, & K. Nakazawa (Proceedings of SPIE Astronomical Telescopes and Instrumentation 2022), 121811T,

2022
[55]

2024, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, V ol

Mori, K., Tomida, H., Nakajima, H., et al. 2024, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, V ol. 13093, Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, ed. J.- W. A. den Herder, S. Nikzad, & K. Nakazawa, 130931I,

2024
[56]

2025, Publ

Noda, H., Mori, K., Tomida, H., et al. 2025, Publ. Astron. Soc. Jpn. Nihon Tenmon Gakkai, 77, S10,

2025
[57]

A., V aughan, B

Nowak, M. A., V aughan, B. A., Wilms, J., Dove, J. B., & Begelman, M. C. 1999, The Astrophysical Journal, 510, 874,

1999
[58]

1971, ApJL, 166, L1,

Oda, M., Gorenstein, P ., Gursky, H., et al. 1971, ApJL, 166, L1,

1971
[59]

A., McClintock, J

Orosz, J. A., McClintock, J. E., Aufdenberg, J. P ., et al. 2011, Astrophys. J., 742, 84,

2011
[60]

S., Adams, J

Porter, F. S., Adams, J. S., Brown, G. V ., et al. 2010, in Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, ed. M. Arnaud, S. S. Murray, & T. Takahashi, V ol. 7732 (SPIE), 77323J,

2010
[61]

S., Boyce, K

Porter, F. S., Boyce, K. R., Chiao, M. P ., et al. 2018, JA TIS, 4, 011218,

2018
[62]

A., et al

Pottschmidt, K., Wilms, J., Nowak, M. A., et al. 2000, å, 357, L17,

2000
[63]

Poutanen, J., V eledina, A., & Beloborodov, A. M. 2023, Astrophys. J. Lett., 949, L10,

2023
[64]

A., & Ibragimov, A

Poutanen, J., Zdziarski, A. A., & Ibragimov, A. 2008, Mon. Not. R. Astron. Soc., 389, 1427,

2008
[65]

H., White, N

Pravdo, S. H., White, N. E., Kondo, Y ., et al. 1980, Astrophys. J., 237, L71,

1980
[66]

Ramachandran, V ., Sander, A. A. C., Oskinova, L. M., et al. 2025, Astron. Astrophys., 698, A37,

2025
[67]

2020, Mon

Rao, A., Gandhi, P ., Knigge, C., et al. 2020, Mon. Not. R. Astron. Soc., 495, 1491,

2020
[68]

A., & McClintock, J

Remillard, R. A., & McClintock, J. E. 2006, ARA&A, 44, 49,

2006
[69]

2023, in High-Resolution X-ray Spectroscopy (Singapore: Springer Nature Singapore), 93–123,

Sato, K., Uchida, Y ., & Ishikawa, K. 2023, in High-Resolution X-ray Spectroscopy (Singapore: Springer Nature Singapore), 93–123,

2023
[70]

S., Cui, W., Canizares, C

Schulz, N. S., Cui, W., Canizares, C. R., et al. 2002, Astrophys. J., 565, 1141,

2002
[71]

F., Kitamoto, S., Wolfs, R., et al

Shipman, R. F., Kitamoto, S., Wolfs, R., et al. 2024, in Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, ed. J.-W. A. den

2024
[72]

J., Kimball, M

Shirron, P . J., Kimball, M. O., James, B. L., et al. 2018, J. Astron. Telesc. Instrum. Syst., 4, 1,

2018
[73]

F., Nathan, E., Hu, K., et al

Steiner, J. F., Nathan, E., Hu, K., et al. 2024, Astrophys. J. Lett., 969, L30,

2024
[74]

2016, Publications of the Astronomical Society of Japan, 68, S17,

Sugimoto, J., Mihara, T., Kitamoto, S., et al. 2016, Publications of the Astronomical Society of Japan, 68, S17,

2016
[75]

O., Owocki, S

Sundqvist, J. O., Owocki, S. P ., & Puls, J. 2018, Astron. Astrophys., 611, A17,

2018
[76]

E., Kelley, R

Szymkowiak, A. E., Kelley, R. L., Moseley, S. H., & Stahle, C. K. 1993, J. Low Temp. Phys., 93, 281,

1993
[77]

2022, in Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, ed

Tamura, K., Hayashi, T., Boissay-Malaquin, R., et al. 2022, in Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, ed. J.-W. A. den Herder, K. Nakazawa, & S. Nikzad (SPIE),

2022
[78]

2024, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, V ol

Tamura, K., Hayashi, T., Boissay-Malaquin, R., et al. 2024, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, V ol. 13093, Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, ed. J.-W. A. den Herder, S. Nikzad, & K. Nakazawa, 130931M,

2024
[79]

1972, ApJL, 177, L5,

Tananbaum, H., Gursky, H., Kellogg, E., Giacconi, R., & Jones, C. 1972, ApJL, 177, L5,

1972
[80]

B., Tucker, W

Tarter, C. B., Tucker, W. H., & Salpeter, E. E. 1969, Astrophys. J., 156, 943,

1969

Showing first 80 references.