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Changing Look AGN: A study of Optical/UV and the Highly Ionized Fe K$\alpha$ X-ray Line Flux Variations Using Photo-Ionization Simulations

T0 review · 2 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash

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Pith's one-line read This paper claims that changing-look AGN transitions are driven by intrinsic accretion-rate changes, and that the highly ionized Fe Kα line is a coronal diagnostic that tracks them.

desk verdict A workmanlike Cloudy study with a solid BLR-insensitivity result and an over-interpreted Fe K coronal-origin claim; worth refereeing, but the coronal location needs to be treated as model input, not output. read the letter →

arxiv 2506.03540 v1 pith:JNDIDYW5 submitted 2025-06-04 astro-ph.GA astro-ph.HE

Tek P. Adhikari , Santanu Mondal , Zhicheng He , Agata Rozanska , Krzysztof Hryniewicz This is my paper
classification astro-ph.GAastro-ph.HE
keywords changing-lookAGNphotoionizationbroademissionlinesFeKalphaaccretiondiskcoronaEddingtonratioMrk1018Seyferttransitions
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

Changing-look AGN flip between spectral types on timescales far shorter than viscous timescales, and this paper asks what actually drives the flip. The authors run photoionization simulations of the broad-line region and the iron Kα region under two continuum-change scenarios: X-ray power-law variation alone, and realistic broadband changes in both disk and X-ray emission. They find that the optical/UV broad lines (Hα, Hβ, Mg II, He II) are nearly indifferent to X-ray-only changes, but respond strongly when the whole spectral energy distribution brightens or dims, as in the well-studied changing-look source Mrk 1018. The highly ionized Fe Kα emission, from H-like and He-like Fe ions, instead tracks the X-ray strength tightly and requires a high-ionization region closer to the black hole than the broad-line region. If correct, the result says changing-look events are genuine accretion-state changes rather than orientation or obscuration effects, and the ionized Fe Kα line is a probe of the corona.

What carries the argument

The load-bearing tool is the Cloudy photoionization code (C23.01) applied to plane-parallel slabs of solar-composition gas with column density $10^{23}\ \mathrm{cm}^{-2}$. The input SED is a big blue bump plus an X-ray power law whose normalization is set by the X-ray-to-optical index $\alpha_{\rm ox}$; the ionization parameter $U = Q(H)/(4\pi r_0^2 n_H c)$ sets the radiation strength. For the realistic Mrk 1018 case, the BLR radius is fixed by a radius-luminosity relation based on the 5100 Å luminosity, gas density is fixed at $n_H = 10^{12}\ \mathrm{cm}^{-3}$, and the Fe K emitting radius is scaled as $R_{\rm FeK} = 10^{-1}$ to $10^{-3} R_{\rm BLR}$, with $10^{-2.5} R_{\rm BLR}$ giving the H-like and He-like dominance. The output quantities that carry the argument are the four broad-line luminosities and the decomposition of the Fe Kα flux into H-like, He-like, hot fluorescent (Fe XVIII–XXIII), and cold fluorescent ($\le$Fe XVII) components.

What would settle it

Take a changing-look AGN such as Mrk 1018 through its bright and faint states with simultaneous optical monitoring and a high-resolution X-ray spectrum, measuring the 6.7 keV He-like Fe Kα line. The model predicts the ionized Fe Kα luminosity falls by about an order of magnitude as $\log(L/L_{\rm Edd})$ drops from $-1.14$ to $-2.27$; if the line flux instead stays constant or rises while the continuum dims, the coronal-origin and accretion-rate-driven picture is wrong. A second check: find a changing-look source with a large Hα disappearance but a constant 5100 Å continuum, which the paper's X-ray-only models say should not happen.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is a clear separation of drivers in AGN line variability. In a grid of photoionization models with the disk emission held fixed and only the X-ray power-law steepening (larger $\alpha_{\rm ox}$), the Hα, Hβ, Mg II, and He II fluxes change by factors of only about 1.2–2.4, far too little to make broad lines appear or disappear. When instead the full spectral energy distribution changes as in Mrk 1018's 2008–2016 transition—bolometric luminosity falling by a factor of 16, with the X-ray luminosity falling about two orders of magnitude—the same lines drop by factors of about 21 (Hα), 26 (Hβ), 24 (Mg II), and 10 (He II) from the highest to the lowest Eddington-ratio state, reproducing the observed dimming from Seyfert 1 to 1.9. For the Fe K region, the simulations show the H-like and He-like Fe components only become dominant when the emitting gas sits at radii near $10^{-2.5}\,R_{\rm BLR}$ with a high ionization parameter; at that location the ionized Fe Kα flux tracks the X-ray strength and falls by about an order of magnitude in the faint state. The paper therefore concludes that highly ionized Fe Kα is produced in the coronal region of the accretion disk, and that a change in the mass accretion rate is the likely trigger of the changing-look phenomenon.

Load-bearing premise

The load-bearing premise is that the broad-line region can be represented by a single gas slab of fixed density $n_H = 10^{12}\ \mathrm{cm}^{-3}$ whose radius is set by the 5100 Å luminosity through a radius-luminosity relation, so that one ionization parameter describes all lines and the Fe K region; if the real BLR spans a range of densities and radii, or is not in photoionization equilibrium during a fast transition, the computed line drops and the inferred coronal radius would change.

Editorial extensions

If this is right

  • If broad-line disappearance in changing-look AGN requires broadband continuum change, then X-ray-only variability campaigns should not be expected to correlate one-to-one with Hα/Hβ type flips; a strong line transition without any 5100 Å change would point to an additional mechanism.
  • The ionized Fe Kα line becomes a practical coronal tracer: its 6.7–6.97 keV flux should rise and fall with the Eddington ratio, giving X-ray spectrometers a way to watch the corona evolve across a changing-look event.
  • The ordering of line responses found here—Hβ dropping most (about 26×) and He II least (about 10×)—gives a quantitative prediction for multi-line monitoring samples of changing-look AGN.
  • If changing-look phenomena are driven by mass accretion changes, Type 1 and Type 2 are not fixed orientation classes but states a single source can cycle through, so AGN demography needs to be treated as a time-dependent process.

Reading between the lines

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

  • Beyond the paper, the single-zone assumption is the place to look first if future data disagree: a BLR with a spread in densities and radii would dilute the predicted factor-of-20 line drops and could reconcile the simulations with changing-look sources that show milder line changes.
  • Beyond the paper, the result implies that a changing-look source caught in its faint state should still show a weak but detectable 6.7 keV Fe Kα component if the accretion flow has not fully shut off; searching for this residual emission is a direct test of the coronal-origin claim.
  • Beyond the paper, the proposed driver could be tested statistically: in a sample of changing-look AGN, the amplitude of the Hβ change should correlate with the amplitude of the 5100 Å continuum change, not with the X-ray change alone.
  • Beyond the paper, if the BLR radius lags the luminosity by a dynamical or recombination time, using a radius-luminosity relation at each epoch could misplace the clouds; time-resolved reverberation mapping during a changing-look event would separate this lag effect from intrinsic accretion change.
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Editorial analysis

A structured set of objections, weighed in public.

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

Referee Report

2 major / 4 minor

Summary. The paper presents Cloudy photoionization simulations of the response of broad-line region (BLR) optical/UV lines (Hα, Hβ, Mg II, He II) and the Fe Kα X-ray line complex to changes in the AGN continuum. Two scenarios are considered: (i) variation of the X-ray power-law only, with fixed disk emission, and (ii) broadband continuum variations as observed in the changing-look AGN Mrk 1018 (using SEDs from Noda & Done 2018). The main findings are that BLR line fluxes are largely insensitive to X-ray-only changes; for Mrk 1018 the simulations reproduce the observed brightening/dimming trends of the BLR lines, although with predicted flux drops that are considerably larger than observed; and that the highly ionized Fe Kα emission from H-like and He-like Fe ions responds strongly to the X-ray strength of the SED, which the authors interpret as evidence that this emission originates in the coronal region of the accretion disk. The paper also concludes that changing-look behavior in AGN is likely driven by intrinsic changes in the accretion rate.

Significance. If the main conclusions hold, the paper supports the view that changing-look AGN transitions reflect genuine changes in the accretion state rather than purely geometrical effects, and it identifies the highly ionized Fe Kα line as a potentially useful coronal diagnostic. The BLR insensitivity to X-ray-only continuum changes is convincingly demonstrated across a wide parameter grid (Figs. 3-7) and is a useful, robust result. The Fe K part, however, is more model-dependent: the conclusion that the emitting region is coronal rests on a chosen radius and density rather than on an independent constraint, and the predicted Fe K luminosities are never compared to observed X-ray line measurements. With appropriate qualification and a comparison to observed Fe K data, the paper would make a solid contribution to the changing-look AGN literature.

major comments (2)
  1. [Section 4.2, Eq. (3), Fig. 21] The conclusion that the highly ionized Fe Kα line originates in the coronal region is not uniquely determined by the modeling because the ionization parameter U = Q(H)/(4πr² n_H c) is degenerate in radius and density. The paper's own Fig. 21 shows that at n_H = 10^9 cm^-3, comparable H-like and He-like Fe K emission already appears at R_FeK = 10^-1 R_BLR, which is about 30 times farther out than the adopted R_FeK = 10^-2.5 R_BLR. Thus the adopted combination (n_H = 10^12 cm^-3, R_FeK = 10^-2.5 R_BLR) is not forced by the data; a lower-density medium at larger radius produces the same qualitative result. Without an independent density constraint, the model does not demonstrate that the emitting region is actually at a coronal distance. I recommend either adding such a constraint or explicitly softening the abstract and conclusion claims from 'origin is in the coronal part' to 'consistent with a coronal origin under the adopted parameters.'
  2. [Section 4.2 and Section 5] The predicted Fe Kα luminosities, equivalent widths, and line ratios are never compared to observed X-ray spectra of Mrk 1018 or any other changing-look AGN. This is a load-bearing gap because the paper's main novelty for the Fe K line is the claim that its variability traces coronal changes. The simulations currently show that a region with the chosen parameters would respond to X-ray flux variations, but they do not demonstrate that such a region exists or that its predicted line strength is consistent with X-ray observations. I recommend adding a quantitative comparison to available X-ray data (e.g., XMM-Newton or Suzaku spectra of Mrk 1018 or similar CL AGN) or, if that is not possible, clearly labeling the Fe K results as a parameter study rather than an empirical reproduction.
minor comments (4)
  1. [Section 4.1] The text states 'we assumed that the BLR gas density is nH = 12 cm^-3', which appears to be a typo for n_H = 10^12 cm^-3. Please correct this.
  2. [Figure 17 and Appendix Figures 21-23] The legend labels contain 'Fluorscent' instead of 'Fluorescent' in Figures 17, 21, 22, and 23. Please correct the spelling.
  3. [Section 3.2 (discussion of Iwasawa et al.)] The text mentions 'Fe XXV and Fe XVI' as high-ionization lines; this is likely a typo, as Fe XVI is not a high-ionization line in this context and the intended reference is probably Fe XXV and Fe XXVI. Please verify and correct.
  4. [Section 4.1, Eq. (4)] The radius-luminosity relation of Bentz et al. (2009) has a reported scatter; including this uncertainty in the propagated Mrk 1018 ionization parameters (Table 1) would make the BLR line predictions more robust and would help assess the significance of the predicted line flux changes.

Circularity Check

1 steps flagged · score 6.0 of 10

Fe K coronal-origin conclusion is the adopted radius–density choice read out via Eq. (3); the Mrk 1018 BLR dimming is a self-contained consistency check, not a fitted prediction.

  1. self definitional [Section 4.2 (Fe Kα emission models), Eqs. (3)–(4), Figs. 17 and 21.]
    "In the next step, and in line with these findings, we consider a model of highly ionized gas that predominantly produces H-like and He-like Fe K emission. ... To estimate the Fe K flux, we adopt a model with a gas density of log[nH] = 12 and log[U] = 3.0. ... If RFeK further decreases to 2.5 orders of magnitude less than RBLR, the total Fe K emission is fully dominated by the emission from He-like and H-like Fe ions. This clearly indicates that the highly ionized Fe Kα emission is produced in the coronal region of the accretion disk in AGNs."

    Eq. (3), U = Q(H)/(4π r0^2 n_H c), makes radius a function of U once n_H and Q(H) are fixed. The paper fixes n_H = 10^12 cm^-3 and adopts log U = 3.0, which is equivalent to placing the gas at R_FeK ≈ 10^-2.5 R_BLR; the H-like/He-like dominance at that radius is then presented as evidence that the line is produced closer to the source, in the corona. That is a restatement of the chosen radius, not a measurement. Fig. 21 shows the degeneracy: at n_H = 10^9 cm^-3, significant H-like/He-like Fe K flux appears at R_FeK = 10^-1 R_BLR. No observed Fe K flux or ratio is compared to break this r–n_H degeneracy, so the coronal-origin claim reduces to the input assumption.

full rationale

The paper's BLR analysis is largely self-contained: Cloudy C23.01 is a public photoionization code, the Mrk 1018 broadband SEDs are taken from Noda & Done (2018), and the BLR radius is set by the external Bentz et al. (2009) R–L relation. The resulting line dimming is a consistency check rather than an independent prediction, because R_BLR^2 scales with L_5100 and the adopted photoionization keeps the line luminosity roughly proportional to the continuum; however, no parameter was fitted to the Mrk 1018 line data, so this is not a circular fit. The Fe K coronal-origin conclusion is circular in the specific sense detailed above: the small emitting radius is an input (via Eq. 3 with n_H = 10^12 cm^-3 and log U = 3), and the H-like/He-like dominance follows from that choice, with the r–n_H degeneracy acknowledged in Fig. 21. The choice of n_H is anchored to the self-cited Adhikari et al. (2016) disk-atmosphere profile, which is load-bearing for the coronal claim. The paper's honesty about the degeneracy and about overestimated BLR line drops (Section 5) keeps the circularity partial rather than total; the independent content (X-ray-only changes do not drive BLR lines, Fe K flux responds to X-ray strength, all lines dim with Eddington ratio) supports a score of 6.

Assumptions & free parameters 8 free parameters · 6 assumptions · 0 invented entities

The central claims rest on several hand-chosen parameters, most notably the Fe K region density, ionization parameter, and radius, which are selected to produce the H-like and He-like Fe K emission that drives the coronal-origin conclusion. The BLR parameters come from the authors' own prior work. No new physical entities are introduced.

free parameters (8)
  • Big Blue Bump temperature T_BB = 5.5e5 K (standard)
    Sets the peak of the UV disk emission in the SED of Eq. 1. Variations to 5e4 and 1e5 K were tested in Fig. 20.
  • X-ray power-law slope alpha_x = -0.2 (standard); -0.5, -1.0 tested
    Sets the hard X-ray spectral shape in Eq. 1. Trend of line responses unchanged across slopes (Fig. 19).
  • Low-energy UV slope alpha_uv = -0.5
    Standard Big Blue Bump slope in Eq. 1; not varied.
  • Gas density n_H for BLR and Fe K region = 1e12 cm^-3
    Chosen from disk-atmosphere models of Adhikari et al. (2016) and BLR studies; affects line fluxes and Fe ionization balance.
  • BLR ionization parameter log U = -2.0 (standard model)
    Standard BLR value from prior work. For Mrk 1018, U is computed from Eq. 3 using the Bentz radius relation, not fixed.
  • Fe K region ionization parameter log U = 3.0
    Chosen to make H-like and He-like Fe ions dominate; the coronal-origin conclusion depends on this choice.
  • Fe K emitting radius R_FeK = 10^-2.5 R_BLR (Mrk 1018 models)
    Chosen to produce dominant H-like and He-like Fe K emission; smaller radii fully ionize Fe and reduce the flux.
  • Column density N_H = 1e23 cm^-2
    Single column for all models; authors state lower columns preserve relative trends.
assumptions (6)
  • domain assumption Solar chemical composition (Grevesse and Sauval 1998) in Cloudy
    Adopted for all models; authors argue constant abundances do not affect relative trends.
  • domain assumption Two-component SED parameterization of Eq. 1 (Big Blue Bump plus X-ray power law)
    Standard representation of AGN continuum; the paper tests variations of slope and temperature but not alternative shapes.
  • domain assumption Constant-density, plane-parallel, open-geometry gas slabs
    Authors argue this is appropriate for BLR; no clumping or pressure laws are modeled.
  • domain assumption Bentz et al. (2009) radius-luminosity relation (Eq. 4) applies to Mrk 1018 at all CL states
    Used to compute R_BLR from L_5100 for each Eddington state; if the BLR is not relaxed, the resulting U values would be wrong.
  • domain assumption Photoionization equilibrium is instantaneous (no time lags)
    Line fluxes respond to the current SED; the paper does not model reverberation delays.
  • domain assumption Cloudy's Fe K emission treatment (stationary gas, no general relativistic effects) is adequate
    Acknowledged limitation in Section 3.2; relevant to the Fe K origin claim.

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Cite this review

Pith. "Pith review of Changing Look AGN: A study of Optical/UV and the Highly Ionized Fe K$\alpha$ X-ray Line Flux Variations Using Photo-Ionization Simulations." pith.science (2026). https://pith.science/paper/JNDIDYW5

@misc{pith2026250603540,
  author       = {Pith},
  title        = {Pith review of: Changing Look AGN: A study of Optical/UV and the Highly Ionized Fe K$\alpha$ X-ray Line Flux Variations Using Photo-Ionization Simulations},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/JNDIDYW5}},
  note         = {Machine review of arXiv:2506.03540}
}
abstract

Significant variability in broad emission line strengths of active galactic nuclei (AGN) over months to years has been observed, often accompanied by intrinsic continuum changes. Such spectral variability challenges the traditional AGN classification scheme, which attributes differences between Type 1 and Type 2 to geometrical effects, as transitions between these types occur on timescales shorter than viscous ones. In this work, using the {\sc cloudy} photo-ionization simulations, we investigated the response of the major emission line fluxes, in the optical/UV and hard X-ray bands, to changes in the intensity and shape of the continuum emission of the AGN under two scenarios: (i) changes in the X-ray power-law while keeping disc emission fixed, and (ii) broadband continuum variations. We demonstrate that BLR line fluxes are insensitive to X-ray power-law changes alone. Considering a well-studied case of the changing-look (CL) AGN Mrk 1018, which exhibits variations in the intrinsic disc emission, as well as the X-ray power-law, our simulations reproduce observed brightening and dimming trends of the BLR emission. Moreover, we show that the highly ionized Fe K$\alpha$ X-ray flux, primarily produced by the H-like and He-like ions of Fe, strongly depends on the X-ray strength of the intrinsic SED. These findings suggest that the origin of highly ionized Fe K$\alpha$ emission is in the coronal part of the accretion disk and that the CL phenomenon can be triggered by intrinsic changes in the accretion properties of AGN.

Figures

Figures reproduced from arXiv: 2506.03540 by the authors.

Figure 2
Figure 2. Disc flux and X-ray flux of the SEDs presented in [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Hα emission plotted for a 3D parameter space: gas density nH, X-ray to optical slope αox, and the ionization parameter U. The BLR clouds are illuminated by the SEDs shown in [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 5
Figure 5. Mg II emission plotted for a 3D parameter space same as described in Fig.3. This variation is further explored in the [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figures from the paper (16 more)
Figure 6
Figure 6. Figure 6: He II emission plotted for a 3D parameter space same as described in Fig.3. 1999) and presented the radial density profile of the disk atmosphere. The values, nH = 1012 and U = 10−2 , adopted here, are inside the dust sublimation radius in their density profile (see th…
Figure 7
Figure 7. Figure 7: Line emission fluxes for all the considered optical/ UV lines, computed by assuming a standard BLR model with nH = 1012 cm−3 , and log U = −2.0, irradiated with the SEDs shown in [PITH_FULL_IMAGE:figures/full_fig_p008_7.png]
Figure 9
Figure 9. Figure 9: 3D plot of emission due to He-like ions of Fe atom. dominated by H-like and He-like Fe ions. However, at lower ionization parameters, the populations of H-like and He-like ions drop significantly, making their emis￾sion negligible and invisible. A similar trend of negl…
Figure 12
Figure 12. Figure 12: 3D plot of fluorescence Fe Kα emission due to the hot ions (Fe XVIII - Fe XXIII). the source of irradiation, i.e., the region of interest for this study. Our result aligns with several findings in the literature, which similarly conclude that a significant portion of …
Figure 11
Figure 11. Figure 11: 3D plot of fluorescent Fe Kα emission due to cold Fe ions with ionization levels ≤ Fe XVII. tively. The cold fluorescence emission contributed by Fe ions with levels ≤ Fe XVII and the hot fluorescence flux from ions with levels in the range Fe XVIII - Fe XXIII are sho…
Figure 13
Figure 13. Figure 13: Contributions to the total Fe K flux estimated from a model of highly ionized gas located close to the source of irradiation, defined by the parameters nH = 1012 cm−3 and log U = 3.0. The total Fe Kα flux (black points) repre￾sents the sum of emission from various Fe …
Figure 14
Figure 14. Figure 14: , reproduced from ND18 (see their [PITH_FULL_IMAGE:figures/full_fig_p011_14.png]
Figure 15
Figure 15. Figure 15: The disc and X-ray power-law luminosities dur￾ing the CL phenomenon of Mrk 1018, obtained by integrat￾ing the continuum luminosities over the defined energy bands versus Eddington ratio is plotted. 0.1 keV, and (ii) the X-ray power-law part, integrated in the energy r…
Figure 16
Figure 16. Figure 16: BLR line luminosities plotted as a function of the change in strength and shape of the irradiation fields, expressed in terms of the varying Eddington ratio L LEdd of Mrk 1018. 4.1. BLR emission models To set up the cloudy models of the emission region, suitable for t…
Figure 17
Figure 17. Figure 17: Plot of Fe Kα emission luminosities for Mrk 1018 SEDs, as shown in [PITH_FULL_IMAGE:figures/full_fig_p014_17.png]
Figure 18
Figure 18. Figure 18: Luminosities of H-like and He-like Fe K emissions, plotted for various gas densities, located at the Fe-emitting radius RFeK = 10−2.5RBLR [PITH_FULL_IMAGE:figures/full_fig_p014_18.png]
Figure 19
Figure 19. Figure 19: Fluxes for the considered optical/UV lines, sim￾ulated using a standard BLR model with nH = 1012 cm−3 , and log U = −2.0, irradiated with SEDs corresponding to various values of αx = −0.2, −0.5 and −1.0 respectively. All other model parameters are identical to those u…
Figure 20
Figure 20. Figure 20: Fluxes for the considered optical/UV lines, sim￾ulated using a standard BLR model with nH = 1012 cm−3 , and log U = −2.0, irradiated with SEDs corresponding to various values of disk temperature TBB = 5 × 104 , 105 and 5×105 K respectively. All other model parameters …
Figure 21
Figure 21. Figure 21: Plot of Fe Kα emission luminosities for Mrk 1018 SEDs, as shown in [PITH_FULL_IMAGE:figures/full_fig_p019_21.png]
Figure 22
Figure 22. Figure 22: Similar to [PITH_FULL_IMAGE:figures/full_fig_p021_22.png]
Figure 23
Figure 23. Figure 23: Similar to [PITH_FULL_IMAGE:figures/full_fig_p022_23.png]

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Works this paper leans on

82 extracted references · 11 canonical work pages

  1. [1]

    , " * write output.state after.block = add.period write newline

    ENTRY address archivePrefix author booktitle chapter doi edition editor eprint howpublished institution journal key month number organization pages publisher school series title misctitle type volume year version url label extra.label sort.label short.list INTEGERS output.state before.all mid.sentence after.sentence after.block FUNCTION init.state.consts ...

  2. [2]

    write newline

    " write newline "" before.all 'output.state := FUNCTION format.url url empty "" new.block "" url * "" * if FUNCTION format.eprint eprint empty "" archivePrefix empty "" archivePrefix "arXiv" = new.block " " eprint * " " * new.block " " eprint * " " * if if if FUNCTION format.doi doi empty "" " " doi * " " * if FUNCTION format.pid doi empty eprint empty ur...

  3. [3]

    gxWػl v^sܮ

    thebibliography [1] 20pt to REFERENCES 6pt =0pt -12pt 10pt plus 3pt =0pt =0pt =1pt plus 1pt =0pt =0pt -12pt =13pt plus 1pt =20pt =13pt plus 1pt \@M =10000 =-1.0em =0pt =0pt 0pt =0pt =1.0em @enumiv\@empty 10000 10000 `\.\@m \@noitemerr \@latex@warning Empty `thebibliography' environment \@ifnextchar \@reference \@latexerr Missing key on reference command E...

    2021

  4. [4]

    Adhikari , T. P. 2019, Photoionization Modelling as a Density Diagnostic of Line Emitting/Absorbing Regions in Active Galactic Nuclei , 10.1007/978-3-030-22737-1

    doi:10.1007/978-3-030-22737-1 2019

  5. [5]

    P., Hryniewicz , K., R \'o \.z a \'n ska , A., Czerny , B., & Ferland , G

    Adhikari , T. P., Hryniewicz , K., R \'o \.z a \'n ska , A., Czerny , B., & Ferland , G. J. 2018, , 856, 78, 10.3847/1538-4357/aab350

    doi:10.3847/1538-4357/aab350 2018

  6. [6]

    P., R \'o \.z a \'n ska , A., Czerny , B., Hryniewicz , K., & Ferland , G

    Adhikari , T. P., R \'o \.z a \'n ska , A., Czerny , B., Hryniewicz , K., & Ferland , G. J. 2016, , 831, 68, 10.3847/0004-637X/831/1/68

    doi:10.3847/0004-637x/831/1/68 2016

  7. [7]

    P., R \'o \.z a \'n ska , A., Hryniewicz , K., Czerny , B., & Behar , E

    Adhikari , T. P., R \'o \.z a \'n ska , A., Hryniewicz , K., Czerny , B., & Behar , E. 2019, , 881, 78, 10.3847/1538-4357/ab2dfc

    doi:10.3847/1538-4357/ab2dfc 2019

  8. [8]

    E., Carraro , R., et al

    Andonie , C., Bauer , F. E., Carraro , R., et al. 2022, , 664, A46, 10.1051/0004-6361/202142473

    doi:10.1051/0004-6361/202142473 2022

Show all 82 references
  1. [9]

    1993, , 31, 473, 10.1146/annurev.aa.31.090193.002353

    Antonucci , R. 1993, , 31, 473, 10.1146/annurev.aa.31.090193.002353

    1993

  2. [10]

    R., Korista , K

    Arav , N., Gabel , J. R., Korista , K. T., et al. 2007, , 658, 829, 10.1086/511666

    2007 doi

  3. [11]

    P., Tollerud , E

    Astropy Collaboration , Robitaille , T. P., Tollerud , E. J., et al. 2013, , 558, A33, 10.1051/0004-6361/201322068

    2013 doi

  4. [12]

    M., Sip o cz , B

    Astropy Collaboration , Price-Whelan , A. M., Sip o cz , B. M., et al. 2018, , 156, 123, 10.3847/1538-3881/aabc4f

    2018 doi

  5. [13]

    R., & Ross , R

    Ballantyne , D. R., & Ross , R. R. 2002, , 332, 777, 10.1046/j.1365-8711.2002.05359.x

    2002

  6. [14]

    Beckmann , V., & Shrader , C. R. 2012, Active Galactic Nuclei

    2012

  7. [15]

    C., Walsh , J

    Bentz , M. C., Walsh , J. L., Barth , A. J., et al. 2009, , 705, 199, 10.1088/0004-637X/705/1/199

    2009 doi

  8. [16]

    2007, , 467, L19, 10.1051/0004-6361:20077331

    Bianchi , S., Guainazzi , M., Matt , G., & Fonseca Bonilla , N. 2007, , 467, L19, 10.1051/0004-6361:20077331

    2007 doi

  9. [17]

    2023, , 59, 327, 10.22201/ia.01851101p.2023.59.02.12

    Chatzikos , M., Bianchi , S., Camilloni , F., et al. 2023, , 59, 327, 10.22201/ia.01851101p.2023.59.02.12

    2023 doi

  10. [18]

    D., Rudy , R

    Cohen , R. D., Rudy , R. J., Puetter , R. C., Ake , T. B., & Foltz , C. B. 1986, , 311, 135, 10.1086/164758

    1986 doi

  11. [19]

    2011, , 525, L8, 10.1051/0004-6361/201016025

    Czerny , B., & Hryniewicz , K. 2011, , 525, L8, 10.1051/0004-6361/201016025

    2011 doi

  12. [20]

    D., De Rosa , G., Croxall , K., et al

    Denney , K. D., De Rosa , G., Croxall , K., et al. 2014, , 796, 134, 10.1088/0004-637X/796/2/134

    2014 doi

  13. [21]

    C., Rees , M

    Fabian , A. C., Rees , M. J., Stella , L., & White , N. E. 1989, , 238, 729, 10.1093/mnras/238.3.729

    1989 doi

  14. [22]

    J., Chatzikos , M., Guzm \'a n , F., et al

    Ferland , G. J., Chatzikos , M., Guzm \'a n , F., et al. 2017, , 53, 385, 10.48550/arXiv.1705.10877

    2017 doi arXiv

  15. [23]

    F., & Kishimoto , M

    Gandhi , P., H \"o nig , S. F., & Kishimoto , M. 2015, , 812, 113, 10.1088/0004-637X/812/2/113

    2015 doi

  16. [24]

    Gaskell , C. M. 2009, , 53, 140, 10.1016/j.newar.2009.09.006

    2009 doi

  17. [25]

    Gohil , R., & Ballantyne , D. R. 2015, , 449, 1449, 10.1093/mnras/stv326

    2015 doi

  18. [26]

    Grevesse , N., & Sauval , A. J. 1998, , 85, 161, 10.1023/A:1005161325181

    1998 doi

  19. [27]

    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, 10.3847/2515-5172/ad0e75

    2023 doi

  20. [28]

    2019, , 883, L44, 10.3847/2041-8213/ab4138

    Guo , H., Sun , M., Liu , X., et al. 2019, , 883, L44, 10.3847/2041-8213/ab4138

    2019 doi

  21. [29]

    A., et al

    Guo , W.-J., Zou , H., Fawcett , V. A., et al. 2024, , 270, 26, 10.3847/1538-4365/ad118a

    2024 doi

  22. [30]

    2021, , 508, 144, 10.1093/mnras/stab2550

    Guolo , M., Ruschel-Dutra , D., Grupe , D., et al. 2021, , 508, 144, 10.1093/mnras/stab2550

    2021 doi

  23. [31]

    K., Ricci , C., Temple , M

    Gupta , K. K., Ricci , C., Temple , M. J., et al. 2024, , 691, A203, 10.1051/0004-6361/202450567

    2024 doi

  24. [32]

    2024, , 530, 4850, 10.1093/mnras/stae1177

    Hagen , S., Done , C., & Edelson , R. 2024, , 530, 4850, 10.1093/mnras/stae1177

    2024 doi

  25. [33]

    2012, in Journal of Physics Conference Series, Vol

    Hryniewicz , K., Niko ajuk , M., & Czerny , B. 2012, in Journal of Physics Conference Series, Vol. 372, Journal of Physics Conference Series (IOP), 012060, 10.1088/1742-6596/372/1/012060

    2012 doi

  26. [34]

    2012, , 537, A86, 10.1051/0004-6361/201118203

    Iwasawa , K., Mainieri , V., Brusa , M., et al. 2012, , 537, A86, 10.1051/0004-6361/201118203

    2012 doi

  27. [35]

    J., et al

    Jana , A., Ricci , C., Temple , M. J., et al. 2024, arXiv e-prints, arXiv:2411.08676. 2411.08676

    2024 arXiv

  28. [36]

    S., Netzer , H., et al

    Kaspi , S., Smith , P. S., Netzer , H., et al. 2000, , 533, 631, 10.1086/308704

    2000 doi

  29. [37]

    L., et al

    Kollatschny , W., Grupe , D., Parker , M. L., et al. 2020, , 638, A91, 10.1051/0004-6361/202037897

    2020 doi

  30. [38]

    S., Reeves , J., et al

    Laha , S., Reynolds , C. S., Reeves , J., et al. 2021, Nature Astronomy, 5, 13, 10.1038/s41550-020-01255-2

    2021 doi

  31. [39]

    M., Yaqoob , T., & Kilgard , R

    LaMassa , S. M., Yaqoob , T., & Kilgard , R. 2017, , 840, 11, 10.3847/1538-4357/aa68df

    2017 doi

  32. [40]

    C., Shu , X

    Liang , W. C., Shu , X. W., Wang , J. X., et al. 2022, Journal of High Energy Astrophysics, 33, 20, 10.1016/j.jheap.2022.01.002

    2022 doi

  33. [41]

    L., Ivezi \'c , Z ., Kochanek , C

    MacLeod , C. L., Ivezi \'c , Z ., Kochanek , C. S., et al. 2010, , 721, 1014, 10.1088/0004-637X/721/2/1014

    2010 doi

  34. [42]

    L., Ross , N

    MacLeod , C. L., Ross , N. P., Lawrence , A., et al. 2016, , 457, 389, 10.1093/mnras/stv2997

    2016 doi

  35. [43]

    2020, , 496, 3412, 10.1093/mnras/staa1683

    Marinucci , A., Bianchi , S., Braito , V., et al. 2020, , 496, 3412, 10.1093/mnras/staa1683

    2020 doi

  36. [44]

    2018, , 478, 5638, 10.1093/mnras/sty1436

    ---. 2018, , 478, 5638, 10.1093/mnras/sty1436

    2018 doi

  37. [45]

    D., Gupta , A., et al

    Mathur , S., Denney , K. D., Gupta , A., et al. 2018, , 866, 123, 10.3847/1538-4357/aadd91

    2018 doi

  38. [46]

    E., Husemann , B., Croom , S

    McElroy , R. E., Husemann , B., Croom , S. M., et al. 2016, , 593, L8, 10.1051/0004-6361/201629102

    2016 doi

  39. [47]

    P., Hryniewicz , K., Stalin , C

    Mondal , S., Adhikari , T. P., Hryniewicz , K., Stalin , C. S., & Pandey , A. 2022, , 662, A77, 10.1051/0004-6361/202243084

    2022 doi

  40. [48]

    P., & Singh , C

    Mondal , S., Adhikari , T. P., & Singh , C. B. 2021, , 505, 1071, 10.1093/mnras/stab1194

    2021 doi

  41. [49]

    D., Yaqoob , T., & Terashima , Y

    Murphy , K. D., Yaqoob , T., & Terashima , Y. 2007, , 666, 96, 10.1086/520039

    2007 doi

  42. [50]

    A., et al

    Nandra , K., Clavel , J., Edelson , R. A., et al. 1998, , 505, 594, 10.1086/306181

    1998 doi

  43. [51]

    1993, , 404, L51, 10.1086/186741

    Netzer , H., & Laor , A. 1993, , 404, L51, 10.1086/186741

    1993 doi

  44. [52]

    N., Yi , W., et al

    Ni , Q., Brandt , W. N., Yi , W., et al. 2020, , 889, L37, 10.3847/2041-8213/ab6d78

    2020 doi

  45. [53]

    2018, , 480, 3898, 10.1093/mnras/sty2032

    Noda , H., & Done , C. 2018, , 480, 3898, 10.1093/mnras/sty2032

    2018 doi

  46. [54]

    2023, , 943, 63, 10.3847/1538-4357/aca963

    Noda , H., Mineta , T., Minezaki , T., et al. 2023, , 943, 63, 10.3847/1538-4357/aca963

    2023 doi

  47. [55]

    L., Winkler , H., Tsygankov , S

    Oknyansky , V. L., Winkler , H., Tsygankov , S. S., et al. 2019, , 483, 558, 10.1093/mnras/sty3133

    2019 doi

  48. [56]

    A., & V \' lchez , J

    P \'e rez-D \' az , B., P \'e rez-Montero , E., Fern \'a ndez-Ontiveros , J. A., & V \' lchez , J. M. 2022, , 666, A115, 10.1051/0004-6361/202243602

    2022 doi

  49. [57]

    N., et al

    Pu , X., Luo , B., Brandt , W. N., et al. 2020, , 900, 141, 10.3847/1538-4357/abacc5

    2020 doi

  50. [58]

    N., Turner , M

    Reeves , J. N., Turner , M. J. L., Pounds , K. A., et al. 2001, , 365, L134, 10.1051/0004-6361:20000424

    2001 doi

  51. [59]

    2023, Nature Astronomy, 7, 1282, 10.1038/s41550-023-02108-4

    Ricci , C., & Trakhtenbrot , B. 2023, Nature Astronomy, 7, 1282, 10.1038/s41550-023-02108-4

    2023 doi

  52. [60]

    2014, , 441, 3622, 10.1093/mnras/stu735

    Ricci , C., Ueda , Y., Paltani , S., et al. 2014, , 441, 3622, 10.1093/mnras/stu735

    2014 doi

  53. [61]

    2020, , 898, L1, 10.3847/2041-8213/ab91a1

    Ricci , C., Kara , E., Loewenstein , M., et al. 2020, , 898, L1, 10.3847/2041-8213/ab91a1

    2020 doi

  54. [62]

    2009, , 700, L6, 10.1088/0004-637X/700/1/L6

    Risaliti , G., Young , M., & Elvis , M. 2009, , 700, L6, 10.1088/0004-637X/700/1/L6

    2009 doi

  55. [63]

    T., & Pojma \'n ski , G

    R \'o \.z a \'n ska , A., Czerny , B., \.Z ycki , P. T., & Pojma \'n ski , G. 1999, , 305, 481, 10.1046/j.1365-8711.1999.02425.x

    1999

  56. [64]

    I., & Sunyaev , R

    Shakura , N. I., & Sunyaev , R. A. 1973, , 24, 337

    1973

  57. [65]

    W., Yaqoob , T., & Wang , J

    Shu , X. W., Yaqoob , T., & Wang , J. X. 2010, , 187, 581, 10.1088/0067-0049/187/2/581

    2010 doi

  58. [66]

    2020, , 641, A167, 10.1051/0004-6361/202038575

    Sniegowska , M., Czerny , B., Bon , E., & Bon , N. 2020, , 641, A167, 10.1051/0004-6361/202038575

    2020 doi

  59. [67]

    A., Gierli \'n ski , M., & Siemiginowska , A

    Sobolewska , M. A., Gierli \'n ski , M., & Siemiginowska , A. 2009, , 394, 1640, 10.1111/j.1365-2966.2009.14436.x

    2009

  60. [68]

    W., Marziani , P., Zwitter , T., Calvani , M., & Dultzin-Hacyan , D

    Sulentic , J. W., Marziani , P., Zwitter , T., Calvani , M., & Dultzin-Hacyan , D. 1998, , 501, 54, 10.1086/305795

    1998 doi

  61. [69]

    1979, , 234, L9, 10.1086/183100

    Tananbaum , H., Avni , Y., Branduardi , G., et al. 1979, , 234, L9, 10.1086/183100

    1979 doi

  62. [70]

    M., & Padovani , P

    Urry , C. M., & Padovani , P. 1995, , 107, 803, 10.1086/133630

    1995 doi

  63. [71]

    2013, , 550, A71, 10.1051/0004-6361/201220443

    Vagnetti , F., Antonucci , M., & Trevese , D. 2013, , 550, A71, 10.1051/0004-6361/201220443

    2013 doi

  64. [72]

    2010, , 519, A17, 10.1051/0004-6361/201014320

    Vagnetti , F., Turriziani , S., Trevese , D., & Antonucci , M. 2010, , 519, A17, 10.1051/0004-6361/201014320

    2010 doi

  65. [73]

    A., & Cignoni , M

    Veronese , S., Vignali , C., Severgnini , P., Matzeu , G. A., & Cignoni , M. 2024, , 683, A131, 10.1051/0004-6361/202348098

    2024 doi

  66. [74]

    2024, arXiv e-prints, arXiv:2407.01737, 10.48550/arXiv.2407.01737

    Wu , Q., Shen , Y., Guo , H., et al. 2024, arXiv e-prints, arXiv:2407.01737, 10.48550/arXiv.2407.01737

    2024 doi arXiv

  67. [75]

    2024, , 973, L25, 10.3847/2041-8213/ad7397

    Xrism Collaboration , Audard , M., Awaki , H., et al. 2024, , 973, L25, 10.3847/2041-8213/ad7397

    2024 doi

  68. [76]

    J., MacLeod , C

    Yang , Q., Green , P. J., MacLeod , C. L., et al. 2023, , 953, 61, 10.3847/1538-4357/acdedd

    2023 doi

  69. [77]

    M., Kallman , T

    Yaqoob , T., George , I. M., Kallman , T. R., et al. 2003, , 596, 85, 10.1086/377687

    2003 doi

  70. [78]

    2004, , 604, 63, 10.1086/381731

    Yaqoob , T., & Padmanabhan , U. 2004, , 604, 63, 10.1086/381731

    2004 doi

  71. [79]

    P., Maccacaro , T., et al

    Zamorani , G., Henry , J. P., Maccacaro , T., et al. 1981, , 245, 357, 10.1086/158815

    1981 doi

  72. [80]

    2024, , 966, 85, 10.3847/1538-4357/ad2f30

    Zeltyn , G., Trakhtenbrot , B., Eracleous , M., et al. 2024, , 966, 85, 10.3847/1538-4357/ad2f30

    2024 doi

  73. [81]

    W., et al

    Zetzl , M., Kollatschny , W., Ochmann , M. W., et al. 2018, , 618, A83, 10.1051/0004-6361/201732506

    2018 doi

  74. [82]

    N., et al

    Zhang , Z., Luo , B., Brandt , W. N., et al. 2023, , 954, 159, 10.3847/1538-4357/ace7c2

    2023 doi

Pith tools

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