Pith. sign in

REVIEW 3 major objections 5 minor 2 cited by

Variability of X-ray polarization of Cyg X-1

T0 review · 3 major / 5 minor · reviewed 2026-08-15 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read Cyg X-1's X-ray polarization doubles when the source turns hard.

desk verdict The hard/soft PD difference and PD-energy trend are robust and worth citing; the orbital PA loop is a real but marginal detection that the abstract overstates. read the letter →

arxiv 2505.03942 v2 pith:VRZTD7BI submitted 2025-05-06 astro-ph.HE

Vadim Kravtsov , Anastasiia Bocharova , Alexandra Veledina , Juri Poutanen , Andrew K. Hughes , Michal Dovčiak , Elise Egron , Fabio Muleri
show 26 more authors
Jakub Podgorny Jiři Svoboda Sofia V. Forsblom Andrei V. Berdyugin Dmitry Blinov Joe S. Bright Francesco Carotenuto David A. Green Adam Ingram Ioannis Liodakis Nikos Mandarakas Anagha P. Nitindala Lauren Rhodes Sergei A. Trushkin Sergey S. Tsygankov Maimouna Brigitte Alessandro Di Marco Noemi Iacolina Henric Krawczynski Fabio La Monaca Vladislav Loktev Guglielmo Mastroserio Pierre-Olivier Petrucci Maura Pilia Francesco Tombesi Andrzej A. Zdziarski
This is my paper · ORCID
classification astro-ph.HE
keywords X-raypolarimetryCygX-1blackholebinariesspectralstatesIXPEorbitalvariabilityjetalignmentaccretiongeometry
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This paper reports three years of X-ray polarimetric monitoring of the black hole X-ray binary Cyg X-1, together with optical and radio observations. It claims that the X-ray polarization degree is tied to the source's spectral state: roughly 4.0% in the hard state, about 2.2% in the soft state, and rising with photon energy in both states. The polarization angle, by contrast, remains independent of state and energy and stays aligned with the radio jet. A linear relation between polarization degree and spectral hardness supports a gradual, continuous change in the polarization-producing geometry rather than an abrupt switch between mechanisms. The paper also finds marginal orbital variations of the angle in the hard state, attributed to scattering of X-rays off intrabinary material, and no superorbital variability at the previously reported 294-day period.

What carries the argument

The load-bearing object is the trajectory traced by the normalized Stokes parameters $(q,u)$ over the 5.6-day orbit. After subtracting an epoch-average center, the residual vector's polarization angle is tested against a linear model in orbital phase, a rotating-vector model in which a full 360-degree loop in the $(q,u)$-plane corresponds to 180 degrees of polarization-angle rotation; significance is assessed with the non-Gaussian likelihood for polarization angles. The state dependence is quantified by fitting polarization degree as a linear function of the IXPE 4-8 keV / 2-4 keV hardness ratio, and the energy dependence by comparing constant-polarization-degree fits to linearly increasing fits in 2-8 keV bins.

What would settle it

Re-observe Cyg X-1 in the hard state several times a year apart, each time covering a full 5.6-day orbit, and fit the $(q,u)$ loop center independently for every epoch. If the centers differ by more than their combined statistical errors, the fixed-center rotating-vector model cannot describe the full campaign, and the claimed one-loop counterclockwise orbital rotation would not be a stable property of the source.

Watch

Extended reading notes

Core claim

The central claim is that the X-ray polarization of Cyg X-1 is a state-dependent quantity with a stable geometry. Across 13 Imaging X-ray Polarimetry Explorer observations spread over 2022-2024, the polarization degree changes from about 4.0% in hard states to about 2.2% in soft states and correlates linearly with spectral hardness (Pearson r=0.92), while the polarization angle remains near -25 degrees, aligned with the radio jet, in every state and at every energy. The rise of polarization degree with energy is statistically significant in both states. In the hard state, phase-resolved analysis shows a closed one-loop trajectory in the $(q,u)$-plane with a counterclockwise rotation of the polarization angle by 180 degrees per orbit, significant at roughly 4 sigma for the full-orbit Epoch 1; the authors interpret this as scattering of the X-ray emission at intrabinary structure rather than a change in the inner flow orientation. No superorbital signal is found at 294 days, with an upper limit of about 5 degrees on polarization-angle variations, and first radio polarization detections give a jet-aligned angle with a fivefold polarization-degree rise during the soft-state transition.

Load-bearing premise

The orbital-variability result assumes the center of the $(q,u)$ loop measured from the single 2022 full-orbit observation stays fixed for all later hard-state observations, so that any residual rotation is assigned to orbital phase rather than to slow drift of the average polarization over years.

Editorial extensions

If this is right

  • A linear polarization-degree/hardness relation means polarization measurements can track the spectral state continuously, and models that require an abrupt change in the X-ray emitting geometry at the state transition are disfavored.
  • Energy-dependent polarization degree with a constant angle across 2-8 keV tightens upper limits on Faraday rotation and on the large-scale magnetic field in the X-ray emitting region.
  • The alignment of X-ray, optical, and radio polarization angles with the jet implies a common projected geometry from the inner accretion flow out to the jet, including a predominantly toroidal magnetic field in the radio-emitting part.
  • The absence of superorbital angle swings above about 5 degrees rules out the earlier suggestion that a 15-20 degree precession tilt of the inner flow explains the high hard-state polarization degree.
  • A single counterclockwise loop per orbit in X-rays, against two clockwise loops in optical polarization, points to different origins for the two bands: scattering at intrabinary material for X-rays rather than the disk-scattering geometry that drives the optical signal.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the polarization-degree/hardness correlation holds as a universal relation across black hole X-ray binaries, a single IXPE pointing with a hardness measurement could serve as a proxy for the full polarimetric state, sidestepping long monitoring campaigns.
  • The apparent anti-correlation between X-ray and radio polarization degree across the hard-to-soft transition, if confirmed with simultaneous data, suggests the jet's synchrotron emission becomes increasingly polarized exactly as the coronal X-ray polarization weakens; a dedicated transition campaign could test whether the two respond to the same geometric change.
  • The model that invokes scattering at intrabinary structure predicts a phase-dependent polarized signal that should also appear in the soft state, diluted by the stronger disk or returning-radiation component; searching for a small orbital loop in soft-state phase-resolved data would test this origin.
  • If high-order Compton scattering dominates the hard-state IXPE band, the polarization-degree rise should flatten above about 8 keV as polarization saturates; a future polarimeter with sensitivity at higher energies could distinguish this from the low-scattering-order scenario proposed here.
Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. The manuscript reports a three-year multiwavelength polarimetric campaign of Cyg X-1, comprising 13 IXPE pointings in 2022-2024 plus optical (DIPol, RoboPol) and radio (VLA, RATAN-600, AMI) monitoring. The main X-ray results are: (i) a state-dependent polarization degree, about 4.0% in the hard state and about 2.2% in the soft state; (ii) a statistically significant increase of PD with photon energy in both states; (iii) a strong correlation (r=0.92) between PD and the 4-8/2-4 keV hardness ratio; (iv) a PA that is independent of spectral state and photon energy and aligned with the radio jet; (v) possible orbital-phase-dependent PA variation in the hard state that is statistically significant mainly for the single full-orbit Epoch 1; and (vi) no detected superorbital variability at P_so=294 d. The authors interpret the orbital signal, if real, as scattering at intrabinary structure, and discuss implications for the geometry of the X-ray-emitting region.

Significance. If the central results hold, this is an important dataset: it is the first multi-epoch X-ray polarimetric campaign covering state transitions in a persistent black hole X-ray binary, and the energy-dependent PD and the PD-hardness correlation will provide strong constraints on Comptonization and disk geometries. The alignment of the PA across radio, optical, and X-ray bands and the cross-source comparison with Swift J1727.8-1613 and GX 339-4 are valuable additions. The analysis is generally careful, including the use of the proper PA probability density of Naghizadeh-Khouei & Clarke for the phase-resolved PA fits. The state-dependent PD and energy-dependent PD results are on solid statistical footing. The orbital variability claim is the least secure part of the paper: the all-epoch evidence is marginal and rests on a loop-center constancy assumption that the authors themselves flag as potentially wrong.

major comments (3)
  1. [Abstract and §3.2] The abstract states 'We find significant orbital changes of PA in the hard state' and attributes them to intrabinary scattering, but the evidence presented in §3.2 is marginal for the full sample: the F-test in §3.2.1 gives p=0.048, and the Monte-Carlo significance for the all-epoch rotating-vector linear-PA model in §3.2.2 is 5.2%. The strong significance is obtained only for Epoch 1 after subtracting the Epoch-1 average (q,u) as the loop center. The authors themselves note in §3.2.2 that the low all-epoch significance 'may result from our assumption that the center of the loop in the (q,u)-plane remains constant over several years of observation.' The orbital variability should therefore be described as tentative or Epoch-1-specific in the abstract and in Section 5, not as a firm detection.
  2. [Abstract and §4.1] The abstract states that the orbital changes are 'attributed to scattering of X-ray emission at the intrabinary structure,' but §4.1 concludes, after considering the precession scenario and the intrabinary-scattering scenario, that 'further quantitative study is needed to draw conclusions on the applicability of this scenario.' This is an unsupported causal attribution as written. The abstract and summary should be reworded to say that the orbital variability, if real, is consistent with intrabinary scattering, or that this scenario requires further quantitative study.
  3. [§3.2.2] The claimed 3-4σ significance for Epoch 1 is obtained after subtracting the mean Stokes parameters ⟨q⟩ and ⟨u⟩ that are computed from the same ten Epoch-1 phase bins. This center-subtraction step introduces a statistical correlation between the residuals, and the Monte-Carlo test described in the text (randomly distributing 10 PAs and fitting the linear model) does not appear to simulate the full Stokes measurement and center-subtraction procedure. The reported Epoch-1 significance should be confirmed with a Monte-Carlo that generates q,u data from the null hypothesis (constant q,u with the observed errors), estimates the center from the simulated data, and then repeats the PA fit and model comparison. This is load-bearing because the Epoch-1 result is the strongest evidence for orbital variability.
minor comments (5)
  1. [§3.2.1] The F-test in §3.2.1 is performed for a model that assumes equal amplitudes r_v for q and u and a fixed π/2 phase offset. The authors should state whether relaxing these restrictions (e.g., allowing an elliptical loop) changes the conclusion, or explicitly justify the circular-loop ansatz.
  2. [§3.2.2] The description of the Monte-Carlo test for the rotating-vector model should specify the number of trials, whether the slope of the linear model is fixed at 1/2 or fitted, and whether the loop-center subtraction is included in the simulation.
  3. [§4.1] The units and definition of μ in the precessing-disk toy model are unclear. As written, with i=153° and PDmax=0.37%, the formula PD=PDmax(1-μ) gives a PD of order 0.7% for μ=cos(153°), not the 3-5% PD shown in Fig. 5. If μ is meant to be |cos i| and PDmax is meant to be 0.37 (dimensionless), this should be stated explicitly.
  4. [Various] Minor editorial issues: 'hard-sate' in §3.1 should be 'hard-state'; the caption of Fig. 5 contains 'of of'; 'χ²/dof=33/12' should be 'χ²/d.o.f.=33/12'; and the quantity exp(-ΔlogL/2)=0.09 in §3.2.2 is a p-value-like quantity and should be labeled as such.
  5. [Fig. 10 and §4.2] The hardness ratio definition changes in Fig. 10 (energy-flux ratio 4-8 keV/2-4 keV) from the photon-flux ratio used earlier in the paper. This is stated in the text, but the figure caption should also flag the definition change so that readers do not compare the two hardness scales directly.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the paper's central results are direct IXPE measurements with stated statistical tests, and the few fitted models are transparently labeled as fits rather than predictions.

full rationale

The main claims—state-dependent X-ray polarization degree, PD increasing with energy, PA alignment with the jet, and the PD–hardness correlation—are direct measurements from IXPE data analyzed with standard tools (xpbintool, PCUBE, energy-binned extraction). No parameter is fitted to a subset of data and then presented as a prediction of a closely related quantity. The PD–hardness relation is a descriptive linear fit to the measured points, not a derived theoretical result, so it does not reduce to its inputs by construction. The orbital-variability analysis is the only place where a fitted quantity is reused: the (q,u) loop center is computed from Epoch 1 data and then subtracted from the same Epoch 1 data to define the variable polarization angle. This is a genuine statistical caveat, and the authors explicitly acknowledge it: 'The low significance of the linear trend is influenced by the outlier (Epoch 11), and may result from our assumption that the center of the loop in the (q,u)-plane remains constant over several years of observation.' However, subtracting a mean does not by itself force the observed ordered 180-degree rotation of PA_v; the Monte-Carlo test for random polarization angles would not produce the favorable log-likelihood unless the phase ordering were real. The high Epoch-1 significance may be somewhat overconfident because the two center parameters are effectively fitted on the same data, but this is a statistical overfitting/robustness concern, not a by-construction equivalence. Similarly, the precessing-disk model in Sect. 4.1 is fitted to the same orbital-loop data it is used to interpret, and the authors state that the intrabinary-scattering attribution needs 'further quantitative study'; this is model interpretation with acknowledged uncertainty, not circularity. Self-citations (e.g., Kravtsov et al. 2023 for ISM correction and optical polarization behavior) are contextual calibration or comparisons and are not load-bearing for the central X-ray state-dependent results, which are self-contained against the IXPE measurements. The abstract's wording that orbital PA changes are 'significant' is stronger than the all-epoch statistics justify, but overstatement of a marginal result is not circular reasoning.

Assumptions & free parameters 4 free parameters · 8 assumptions · 0 invented entities

The paper introduces no new physical entities. The intrabinary scattering and precessing inner flow invoked in the discussion are pre-existing hypotheses, not new postulates.

free parameters (4)
  • Hardness threshold between hard and soft states = 0.4 (adopted)
    Used in Sect. 2.1/3.1 to split the 13 epochs into hard and soft states; the paper notes it 'does not treat the intermediate state as a separate spectral state.'
  • Variable-component amplitude r_v = not quoted
    Free amplitude in the sinusoidal model of Eq. (1) fitted to phase-resolved q and u in Sect. 3.2.1; the best-fit chi2 is reported but r_v is not given in the text.
  • PDmax in precessing-disk model = 0.37%
    Chosen in Sect. 4.1 ('PDmax=0.37%') so that the model reproduces the amplitude of the observed PD orbital variation; not independently derived.
  • Tilt angle beta in precessing-disk model = 2 deg
    Fitted in Sect. 4.1 to match the amplitude of PA variations around the orbit; this is the key parameter used to argue for a small tilt.
assumptions (8)
  • standard math Standard error propagation and Gaussian statistics apply to the measured Stokes parameters and to the F-test and likelihood ratio comparisons.
    Used throughout Sect. 3.2 to compute significances of orbital variability; assumes the quoted 1-sigma errors are correct and independent.
  • domain assumption IXPE instrumental calibration and background subtraction are correct for all 13 pointings.
    The source region is a 60'' circle and Level 2 data are reduced with CalDB v13; if calibration or background are wrong, the PD/PA values shift.
  • domain assumption The interstellar polarization correction for the optical data (Table 2 of Kravtsov et al. 2023) is accurate.
    Used in Sect. 2.2.1 to derive intrinsic optical PD/PA; the claimed multiwavelength PA alignment depends on this correction.
  • domain assumption The IXPE hardness ratio (4-8 keV / 2-4 keV) is a valid tracer of the accretion spectral state.
    Used in Sect. 3.1 to establish the PD-hardness correlation and to classify epochs; a different hardness definition or energy binning could shift the relation.
  • ad hoc to paper The center of the (q,u) loop is constant over the years of hard-state observations and equal to the Epoch 1 average.
    Assumed in the rotating-vector-model analysis of Sect. 3.2.2; the authors explicitly note that a changing center could explain the low significance.
  • ad hoc to paper The variable component in Eq. (1) has a constant amplitude r_v and a fixed pi/2 phase offset between q and u.
    Adopted in Sect. 3.2.1 'to keep the number of parameters to minimum'; a more general model could change the F-test result.
  • ad hoc to paper In the precessing-disk toy model, PD depends linearly on cos(inclination) as PD = PDmax(1 - mu) with the orbital inclination fixed to i=153 deg.
    Used in Sect. 4.1 to interpret the orbital loop; the authors state the actual angular dependence may be more complex.
  • domain assumption Radio PA aligned with the jet implies a predominantly toroidal magnetic field in the jet.
    Invoked in Sect. 4.3 to interpret the first radio polarization detection; standard synchrotron theory but not directly tested here.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Variability of X-ray polarization of Cyg X-1." pith.science (2026). https://pith.science/paper/VRZTD7BI

@misc{pith2026250503942,
  author       = {Pith},
  title        = {Pith review of: Variability of X-ray polarization of Cyg X-1},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/VRZTD7BI}},
  note         = {Machine review of arXiv:2505.03942}
}
abstract

We present the results of a three-year X-ray, optical, and radio polarimetric monitoring campaign of the prototypical black hole X-ray binary Cyg X-1, conducted from 2022 to 2024. The X-ray polarization of Cyg X-1 was measured 13 times with the Imaging X-ray Polarimetry Explorer (IXPE), covering both hard and soft spectral states. The X-ray polarization degree (PD) in the hard state was found to be $\approx4.0\%$, roughly twice as high as in the soft state, where it was around $2.2\%$. In both states, a statistically significant increase of PD with the energy was found. Moreover, a linear relation between PD and spectral hardness suggests a gradual and continuous evolution of the polarization properties, rather than an abrupt change of polarization production mechanism between states. The polarization angle (PA) was independent of the spectral state and showed no trend with the photon energy. The X-ray PA is well aligned with the orientation of the radio jet, as well as the optical and radio PAs. We find significant orbital changes of PA in the hard state, which we attribute to scattering of X-ray emission at intrabinary structure. No significant superorbital variability in PD or PA was found at the period $P_{\rm{so}}$ = 294 d. We also find no correlation between the X-ray and optical polarization; if any, there is a long-term anti-correlation between the X-ray PD and the radio PD.

Figures

Figures reproduced from arXiv: 2505.03942 by the authors.

Figure 1
Figure 1. Spectral and polarization properties of Cyg X-1 for each IXPE observation with hardness shown in color. Numbers represent the obser￾vation’s epoch in accordance with [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Multiwavelength results on Cyg X-1. Panels (a) and (b): PD and PA of polarization in X-rays (IXPE), optical (DIPol) and radio (VLA). Panel (c): light curve in the radio as measured with AMI, VLA and RATAN 600. Panel (d): MAXI photon flux in 2–20 keV. Panel (e): MAXI hardness. In panels (d) and (e), we show all MAXI data in gray, highlighting in color only the data obtained simultaneously with IXPE. MJD0 = 59653 (202… view at source ↗
Figure 3
Figure 3. Energy dependence of polarization properties of Cyg X-1 in the hard and soft states. 2 4 PD, % HS SS 0.0 0.2 0.4 0.6 0.8 Hardness ratio −40 −20 0 PA, deg [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figures from the paper (7 more)
Figure 4
Figure 4. Figure 4: Dependence of PD and PA of Cyg X-1 on spectral hardness. The dashed and dash-dotted horizontal lines show average values in the hard- and soft-states, respectively. The dotted line with 1, 2, and 3σ confidence intervals shows a linear fit to the PD. 3. Results 3.1. Lon…
Figure 5
Figure 5. Figure 5: Orbital phase-resolved polarization of of Cyg X-1 in the hard state. Left panel: Variation of the normalized Stokes parameters. The numbers represent the orbital phase bins from 1 to 10 and the colors correspond to the superorbital phase (right color bar). Right panel:…
Figure 6
Figure 6. Figure 6: Orbital phase-resolved normalized Stokes parameters of Cyg X-1 in the hard state. Dashed black and solid blue lines correspond to best-fit constant and sinusoidal models, respectively. See Sect. 3.2 for details. 3.2.1. Constant versus sine-wave To assess the statistica…
Figure 7
Figure 7. Figure 7: Angle ∆χ as a function of the orbital phase in Cyg X-1. The solid line shows the best fit to the Epoch 1 data with the linear model (7) described in Sect. 3.2. To account for this uncertainty, we adopted an alternative ap￾proach to test for the presence of orbital vari…
Figure 8
Figure 8. Figure 8: Smoothed histogram of the observed PA of Cyg X-1 in X-rays (red), radio (orange), and optical (blue). Each observation here is repre￾sented as a Gaussian with the standard deviation equal to the error and the sum of those is divided by the number of observations. Graph…
Figure 9
Figure 9. Figure 9: Sketch of considered precessing disk geometry for two cases: i < 90◦ and i > 90◦ . disk axis on the sky follows the sense of rotation of the com￾pact object around the supergiant (see [PITH_FULL_IMAGE:figures/full_fig_p009_9.png]
Figure 10
Figure 10. Figure 10: Dependence of PD on spectral hardness for Cyg X-1, Swift J1727.8−1613 and GX 339−4. For consistency, the hardness ra￾tio has been calculated the same way for all objects as a ratio of energy flux in 4–8 keV to that in 2–4 keV as measured by IXPE. The dotted line with …

Discussion (0). Continue with ORCID to comment.

Forward citations

Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Unchanged X-Ray Polarization During Accretion Dips in the Low Hard State of Cygnus X-1

    astro-ph.HE 2026-07 conditional novelty 6.0 of 10

    During Cygnus X-1 accretion dips the 2–8 keV polarization is unchanged within errors, indicating the absorbed disk does not contribute and supporting an extended oblate corona.

  2. Exploring MAXI J1744-294: IXPE insights into a Newly Discovered X-ray Transient

    astro-ph.HE 2025-06 accept novelty 4.0 of 10

    A new IXPE observation finds no X-ray polarization from MAXI J1744-294 and uses the 1.3% upper limit to constrain the accretion disk inclination to roughly 38-71 degrees, depending on spin and atmosphere albedo.

Reference graph

Works this paper leans on

95 extracted references · 38 canonical work pages · cited by 2 Pith papers

  1. [1]

    2024, A&A, 688, A220

    Ahlberg, V ., Kravtsov, V ., & Poutanen, J. 2024, A&A, 688, A220

    2024

  2. [2]

    2021, Astroparticle Physics, 133, 102628

    Baldini, L., Barbanera, M., Bellazzini, R., et al. 2021, Astroparticle Physics, 133, 102628

    2021

  3. [3]

    D., et al

    Baldini, L., Bucciantini, N., Lalla, N. D., et al. 2022, SoftwareX, 19, 101194

    2022

  4. [4]

    M., Press, W

    Bardeen, J. M., Press, W. H., & Teukolsky, S. A. 1972, ApJ, 178, 347

    1972

  5. [5]

    & Done, C

    Barnier, S. & Done, C. 2024, ApJ, 977, 201

    2024

  6. [6]

    Belloni, T. M. 2010, in Lecture Notes in Physics, V ol. 794, The Jet Paradigm (Berlin Heidelberg: Springer Verlag), 53

    2010

  7. [7]

    Beloborodov, A. M. & Poutanen, J. 1999, ApJ, 517, L77

    1999

  8. [8]

    Bjornsson, C. I. & Blumenthal, G. R. 1982, ApJ, 259, 805

    1982

Show all 95 references
  1. [9]

    2021, MNRAS, 501, 3715

    Blinov, D., Kiehlmann, S., Pavlidou, V ., et al. 2021, MNRAS, 501, 3715

    2021

  2. [10]

    Bochkarev, N. G. & Karitskaya, E. A. 1983, Soviet Astronomy Letters, 9, 6

    1983

  3. [11]

    T., Chubb, T

    Bowyer, S., Byram, E. T., Chubb, T. A., & Friedman, H. 1965, Science, 147, 394

    1965

  4. [12]

    Brentjens, M. A. & de Bruyn, A. G. 2005, A&A, 441, 1217

    2005

  5. [13]

    & Svoboda, J

    Brigitte, M. & Svoboda, J. 2025, in WDS’24 Proc. Contrib. Papers, Physics, ed. J. Šafránková & J. Pavl˚ u (Prague: Matfyzpress), 178–184

    2025

  6. [14]

    Brocksopp, C., Miller-Jones, J. C. A., Fender, R. P., & Stappers, B. W. 2007, MNRAS, 378, 1111

    2007

  7. [15]

    C., McLean, I

    Brown, J. C., McLean, I. S., & Emslie, A. G. 1978, A&A, 68, 415 CASA Team, Bean, B., Bhatnagar, S., et al. 2022, PASP, 134, 114501

    1978

  8. [16]

    1960, Radiative transfer (New York: Dover Publications, Inc.)

    Chandrasekhar, S. 1960, Radiative transfer (New York: Dover Publications, Inc.)

    1960

  9. [17]

    Connors, P. A. & Stark, R. F. 1977, Nature, 269, 128

    1977

  10. [18]

    P., Tzioumis, A

    Corbel, S., Fender, R. P., Tzioumis, A. K., et al. 2000, A&A, 359, 251

    2000

  11. [19]

    A., Coriat, M., Miller-Jones, J

    Curran, P. A., Coriat, M., Miller-Jones, J. C. A., et al. 2014, MNRAS, 437, 3265 Di Gesu, L., Marshall, H. L., Ehlert, S. R., et al. 2023, Nature Astronomy, 7, 1245 Di Marco, A., Fabiani, S., La Monaca, F., et al. 2022, AJ, 164, 103

    2014

  12. [20]

    2007, A&AR, 15, 1 Dovˇciak, M., Karas, V ., & Matt, G

    Done, C., Gierli´nski, M., & Kubota, A. 2007, A&AR, 15, 1 Dovˇciak, M., Karas, V ., & Matt, G. 2004, MNRAS, 355, 1005 Dovˇciak, M., Muleri, F., Goosmann, R. W., Karas, V ., & Matt, G. 2008, MNRAS, 391, 32

    2007

  13. [21]

    P., Stirling, A

    Fender, R. P., Stirling, A. M., Spencer, R. E., et al. 2006, MNRAS, 369, 603

    2006

  14. [22]

    2025, A&A, 696, A224

    Poutanen, J. 2025, A&A, 696, A224

    2025

  15. [23]

    2010, ApJ, 719, L79 Gierli´nski, M., Zdziarski, A

    Fragos, T., Tremmel, M., Rantsiou, E., & Belczynski, K. 2010, ApJ, 719, L79 Gierli´nski, M., Zdziarski, A. A., Done, C., et al. 1997, MNRAS, 288, 958 Gierli´nski, M., Zdziarski, A. A., Poutanen, J., et al. 1999, MNRAS, 309, 496

    2010

  16. [24]

    Gies, D. R. & Bolton, C. T. 1986, ApJ, 304, 371

    1986

  17. [25]

    & Hjellming, R

    Han, X. & Hjellming, R. M. 1992, ApJ, 400, 304

    1992

  18. [26]

    C., Hunstead, R

    Hannikainen, D. C., Hunstead, R. W., Campbell-Wilson, D., et al. 2000, ApJ, 540, 521

    2000

  19. [27]

    C., et al

    Hickish, J., Razavi-Ghods, N., Perrott, Y . C., et al. 2018, MNRAS, 475, 5677

    2018

  20. [28]

    A., & Poutanen, J

    Ibragimov, A., Zdziarski, A. A., & Poutanen, J. 2007, MNRAS, 381, 723

    2007

  21. [29]

    2024, ApJ, 968, 76

    Ingram, A., Bollemeijer, N., Veledina, A., et al. 2024, ApJ, 968, 76

    2024

  22. [30]

    2015, ApJ, 815, 53

    Kallman, T., Dorodnitsyn, A., & Blondin, J. 2015, ApJ, 815, 53

    2015

  23. [31]

    A., V oloshina, I

    Karitskaya, E. A., V oloshina, I. B., Goranskii, V . P., et al. 2001, Astronomy Re- ports, 45, 350

    2001

  24. [32]

    C., Barbour, M

    Kemp, J. C., Barbour, M. S., Henson, G. D., et al. 1983, ApJ, 271, L65

    1983

  25. [33]

    E., Di Gesu, L., Liodakis, I., et al

    Kim, D. E., Di Gesu, L., Liodakis, I., et al. 2024, A&A, 681, A12

    2024

  26. [34]

    V ., Kosenkov, I

    Kravtsov, V ., Berdyugin, A. V ., Kosenkov, I. A., et al. 2022, MNRAS, 514, 2479

    2022

  27. [35]

    V ., Piirola, V ., et al

    Kravtsov, V ., Berdyugin, A. V ., Piirola, V ., et al. 2020, A&A, 643, A170

    2020

  28. [36]

    V ., et al

    Kravtsov, V ., Veledina, A., Berdyugin, A. V ., et al. 2023, A&A, 678, A58

    2023

  29. [37]

    & Beheshtipour, B

    Krawczynski, H. & Beheshtipour, B. 2022, ApJ, 934, 4

    2022

  30. [38]

    2022, Science, 378, 650

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

    2022

  31. [39]

    2006, MNRAS, 368, 1025

    Kitamoto, S. 2006, MNRAS, 368, 1025

    2006

  32. [40]

    Li, L.-X., Narayan, R., & McClintock, J. E. 2009, ApJ, 691, 847 Article number, page 11 A&A proofs:manuscript no. aa55411-25

    2009

  33. [41]

    2022, A&A, 660, A25

    Loktev, V ., Veledina, A., & Poutanen, J. 2022, A&A, 660, A25

    2022

  34. [42]

    Loktev, V ., Veledina, A., Poutanen, J., Nättilä, J., & Suleimanov, V . F. 2024, A&A, 685, A84

    2024

  35. [43]

    Longair, M. S. 1994, High energy astrophysics, V ol. 2 (Cambridge: Cambridge University Press)

    1994

  36. [44]

    I., & Gabuzda, D

    Lyutikov, M., Pariev, V . I., & Gabuzda, D. C. 2005, MNRAS, 360, 869

    2005

  37. [45]

    & Belmont, R

    Malzac, J. & Belmont, R. 2009, MNRAS, 392, 570

    2009

  38. [46]

    C., et al

    Mastroserio, G., De Marco, B., Baglio, M. C., et al. 2025, ApJ, 978, L19

    2025

  39. [47]

    2009, PASJ, 61, 999

    Matsuoka, M., Kawasaki, K., Ueno, S., et al. 2009, PASJ, 61, 999

    2009

  40. [48]

    A., & Weisskopf, M

    Meszaros, P., Novick, R., Szentgyorgyi, A., Chanan, G. A., & Weisskopf, M. C. 1988, ApJ, 324, 1056

    1988

  41. [49]

    Miller-Jones, J. C. A., Bahramian, A., Orosz, J. A., et al. 2021, Science, 371, 1046

    2021

  42. [50]

    & Clarke, D

    Naghizadeh-Khouei, J. & Clarke, D. 1993, A&A, 274, 968

    1993

  43. [51]

    P., Veledina, A., & Poutanen, J

    Nitindala, A. P., Veledina, A., & Poutanen, J. 2025, A&A, 694, A230

    2025

  44. [52]

    Novikov, I. D. & Thorne, K. S. 1973, in Black Holes (Les Astres Occlus), ed. C. DeWitt & B. DeWitt (New York: Gordon and Breach), 343–450

    1973

  45. [53]

    R., McKiconley, B., Hurley-Walker, N., et al

    Offringa, A. R., McKiconley, B., Hurley-Walker, N., et al. 2014, MNRAS, 444, 606

    2014

  46. [54]

    A., McClintock, J

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

    2011

  47. [55]

    1994, A&A, 284, 331

    Ott, M., Witzel, A., Quirrenbach, A., et al. 1994, A&A, 284, 331

    1994

  48. [56]

    E., Middei, R., et al

    Pacciani, L., Kim, D. E., Middei, R., et al. 2025, ApJ, 983, 78

    2025

  49. [57]

    2015, MNRAS, 452, 715

    Panopoulou, G., Tassis, K., Blinov, D., et al. 2015, MNRAS, 452, 715

    2015

  50. [58]

    2014, in Proc

    Piirola, V ., Berdyugin, A., & Berdyugina, S. 2014, in Proc. SPIE, V ol. 9147, Ground-based and Airborne Instrumentation for Astronomy V , ed. S. K. Ram- say, I. S. McLean, & H. Takami, 91478I

    2014

  51. [59]

    C., et al

    Piirola, V ., Berdyugin, A., Frisch, P. C., et al. 2020, A&A, 635, A46

    2020

  52. [60]

    A., Berdyugin, A

    Piirola, V ., Kosenkov, I. A., Berdyugin, A. V ., Berdyugina, S. V ., & Poutanen, J. 2021, AJ, 161, 20 Podgorný, J., Svoboda, J., Dovˇciak, M., et al. 2024, A&A, 686, L12

    2021

  53. [61]

    & Svensson, R

    Poutanen, J. & Svensson, R. 1996, ApJ, 470, 249

    1996

  54. [62]

    Poutanen, J., Veledina, A., & Beloborodov, A. M. 2023, ApJ, 949, L10

    2023

  55. [63]

    Poutanen, J., Veledina, A., & Zdziarski, A. A. 2018, A&A, 614, A79

    2018

  56. [64]

    & Vurm, I

    Poutanen, J. & Vurm, I. 2009, ApJ, 690, L97

    2009

  57. [65]

    A., & Ibragimov, A

    Poutanen, J., Zdziarski, A. A., & Ibragimov, A. 2008, MNRAS, 389, 1427

    2008

  58. [66]

    C., Terrell, J., & Holt, S

    Priedhorsky, W. C., Terrell, J., & Holt, S. S. 1983, ApJ, 270, 233

    1983

  59. [67]

    R., Van Eck, C

    Purcell, C. R., Van Eck, C. L., West, J., Sun, X. H., & Gaensler, B. M. 2020, RM- Tools: Rotation measure (RM) synthesis and Stokes QU-fitting, Astrophysics Source Code Library, record ascl:2005.003

    2020

  60. [68]

    & Cooke, D

    Radhakrishnan, V . & Cooke, D. J. 1969, Astrophys. Lett., 3, 225

    1969

  61. [69]

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

    2025

  62. [70]

    N., Rajarshi, C

    Ramaprakash, A. N., Rajarshi, C. V ., Das, H. K., et al. 2019, MNRAS, 485, 2355

    2019

  63. [71]

    2024, ApJ, 962, 34

    Rankin, J., Kravtsov, V ., Muleri, F., et al. 2024, ApJ, 962, 34

    2024

  64. [72]

    2020, MNRAS, 495, 1491

    Rao, A., Gandhi, P., Knigge, C., et al. 2020, MNRAS, 495, 1491

    2020

  65. [73]

    Rees, M. J. 1975, MNRAS, 171, 457

    1975

  66. [74]

    D., Miller-Jones, J

    Russell, T. D., Miller-Jones, J. C. A., Curran, P. A., et al. 2015, MNRAS, 450, 1745

    2015

  67. [75]

    Schnittman, J. D. & Krolik, J. H. 2009, ApJ, 701, 1175

    2009

  68. [76]

    Shakura, N. I. & Sunyaev, R. A. 1973, A&A, 500, 33

    1973

  69. [77]

    Sobolev, V . V . 1963, A treatise on radiative transfer (Princeton: Van Nostrand)

    1963

  70. [78]

    2021, AJ, 162, 208

    Soffitta, P., Baldini, L., Bellazzini, R., et al. 2021, AJ, 162, 208

    2021

  71. [79]

    Stark, R. F. & Connors, P. A. 1977, Nature, 266, 429

    1977

  72. [80]

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

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

    2024

  73. [81]

    M., Spencer, R

    Stirling, A. M., Spencer, R. E., de la Force, C. J., et al. 2001, MNRAS, 327, 1273

    2001

  74. [82]

    F., Forsblom, S

    Suleimanov, V . F., Forsblom, S. V ., Tsygankov, S. S., et al. 2023, A&A, 678, A119

    2023

  75. [83]

    Sunyaev, R. A. & Titarchuk, L. G. 1980, A&A, 86, 121

    1980

  76. [84]

    Sunyaev, R. A. & Titarchuk, L. G. 1985, A&A, 143, 374

    1985

  77. [85]

    F., et al

    Svoboda, J., Dovˇciak, M., Steiner, J. F., et al. 2024, ApJ, 966, L35

    2024

  78. [86]

    1972, ApJ, 177, L5

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

    1972

  79. [87]

    2023, ApJ, 958, L16

    Veledina, A., Muleri, F., Dovˇciak, M., et al. 2023, ApJ, 958, L16

    2023

  80. [88]

    2024, Nature Astronomy, 8, 1031

    Veledina, A., Muleri, F., Poutanen, J., et al. 2024, Nature Astronomy, 8, 1031

    2024

  81. [89]

    2013, MNRAS, 430, 3196

    Veledina, A., Poutanen, J., & Vurm, I. 2013, MNRAS, 430, 3196

    2013

  82. [90]

    C., Soffitta, P., Baldini, L., et al

    Weisskopf, M. C., Soffitta, P., Baldini, L., et al. 2022, JATIS, 8, 026002

    2022

  83. [91]

    Westfold, K. C. 1959, ApJ, 130, 241

    1959

  84. [92]

    Zdziarski, A. A. & Gierli´nski, M. 2004, Progress of Theoretical Physics Supple- ment, 155, 99

    2004

  85. [93]

    A., Gierli ´nski, M., Mikołajewska, J., et al

    Zdziarski, A. A., Gierli ´nski, M., Mikołajewska, J., et al. 2004, MNRAS, 351, 791

    2004

  86. [94]

    A., Pooley, G

    Zdziarski, A. A., Pooley, G. G., & Skinner, G. K. 2011, MNRAS, 412, 1985

    2011

  87. [95]

    Zwart, J. T. L., Barker, R. W., Biddulph, P., et al. 2008, MNRAS, 391, 1545 1 Department of Physics and Astronomy, FI-20014 University of

    2008

Pith tools

Reviewed August 15, 2026 · model on record in the stance chip above.