Discarding the disc in a changing state AGN: the UV/X-ray relation in NGC 4151

Chris Done; Ra'ad D. Mahmoud

REVIEW 3 major objections 5 minor 73 references

Discarding the disc in a changing state AGN: the UV/X-ray relation in NGC 4151

T0 review · 3 major / 5 minor · reviewed 2026-08-14 · deepseek-v4-flash

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Pith's one-line read The paper claims that the ultraviolet light of NGC 4151 is produced by X-ray reprocessing in broad-line-region gas, not by an inner accretion disc, which had vanished into a hot flow.

desk verdict A strong negative result on inner-disc reprocessing in NGC 4151, with a plausible but undertested BLR-scale interpretation. read the letter →

arxiv 1908.05461 v2 pith:T46SHA4M submitted 2019-08-15 astro-ph.HE

Ra'ad D. Mahmoud , Chris Done This is my paper · ORCID

classification astro-ph.HE

keywords accretiondiscsactivegalacticnucleireverberationmappingX-rayreprocessingbroadlineregionchanging-stateAGNNGC4151spectraltiming

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 asks where the ultraviolet emission of the active galaxy NGC 4151 is produced during a faint, changing-state phase. Building a spectral-timing model with an outer disc, a warm Comptonising layer, and a hot X-ray corona, the authors fit the time-averaged spectrum and then use the observed 15-50 keV light curve to predict how the near-ultraviolet should vary if the UV is simply reprocessed X-rays from optically thick material within a few hundred gravitational radii. That prediction fails badly: the model UV is far too fast and too strongly correlated with the X-rays. The data are instead matched by a linear reprocessing response spread over 1.5-20 light-days, the size scale of the broad line region, and the authors conclude that NGC 4151's inner thin disc had effectively been replaced by a hot, radiatively inefficient flow during the campaign, at a luminosity near 1.4 percent Eddington. A sympathetic reader cares because this is the first time the full bolometric X-ray driver, rather than a soft X-ray proxy, has been used to test the standard reprocessing picture of AGN optical and UV continuum.

What carries the argument

The central machinery is the agnsed spectral-timing model: it assumes Novikov-Thorne gravitational dissipation at each radius, but thermalises it to a blackbody only outside the warm-Compton radius, releases it in a warm Comptonising layer at intermediate radii, and puts the innermost radii into a hot corona, so the UV in the canonical fit originates at 90-390 $R_g$. The companion tool is an impulse-response decomposition in which the UVW1 light curve is a constant, plus a slow component formed by convolving the BAT light curve with a free impulse-response function, plus a small fast component. A double-Gaussian and then an exponentially modified double-Gaussian impulse response localise the slow component to 1.5-20 light-days, and the light-travel-time argument against any alternative at less than 1.5 light-days is what rules out the disc.

What would settle it

Higher-cadence, simultaneous monitoring with a hard-X-ray instrument covering above 50 keV would settle the picture: if the UVW1 versus greater-than-50 keV cross-correlation shows a peak at lags below 1.5 days, the claimed absence of inner optically thick material is wrong. A high signal-to-noise X-ray spectrum showing a relativistically broadened iron line from within roughly 1.5 light-days would also directly contradict the truncated-flow geometry.

Watch

Extended reading notes

Core claim

The central discovery is that the near-ultraviolet (UVW1) light curve of NGC 4151 cannot be powered by optically thick accretion-disc material inside roughly 1.5 light-days, and can instead be powered by X-ray reprocessing in broad-line-region gas. The canonical spectral fit places the UV source in a warm Comptonising region spanning 90-390 gravitational radii from the black hole, but when the Swift BAT hard X-ray light curve is convolved through the light-travel-time impulse response of that geometry, the predicted UV variability has far too much power on sub-day timescales and too high a correlation with the X-rays. Replacing the physical model with a free impulse-response function gives a good fit with 90 percent of the UV flux responding on lags of 1.5-20 days, matching known BLR size scales, and only 5-10 percent responding fast. The paper's conclusion is that the inner disc was absent during this epoch, replaced by an optically thin hot flow, and that the UV continuum is dominated by diffuse emission from dense BLR gas, with the inferred luminosity of 1.4 percent Eddington placing the source in the changing-state regime.

Load-bearing premise

The argument assumes the Swift BAT 15-50 keV light curve tracks the true bolometric X-ray luminosity that drives reprocessing; if the flux above 50 keV varied independently, both the failure of the disc model and the recovered 1.5-20 day response would be artifacts.

Editorial extensions

If this is right

The standard irradiated-disc plus warm-Compton geometry cannot produce the observed UVW1 light curve of NGC 4151, even when the soft-excess region is removed or the corona is made vertically extended.
A linear impulse response with delays of 1.5-20 days reproduces the UVW1 light curve, meaning the slow UV variability is consistent with reprocessing by dense gas in the broad line region.
Only about 5-10 percent of the UVW1 flux can be fast-correlated with the hard X-rays, leaving no room for a significant disc or warm-Compton contribution inside roughly 1.5 light-days.
The inner accretion flow in NGC 4151 at this epoch is inferred to be radiatively inefficient, consistent with its low Eddington fraction and with the absence of a relativistically broadened iron line.

Reading between the lines

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

A direct test of the paper's logic: monitor a sample of AGN across the Eddington-fraction range 0.01-0.03 with simultaneous UV and greater-than-10 keV X-ray coverage and check whether fast (less than 1 day) UV response appears as the Eddington fraction rises, as expected if the thin disc reforms.
If BLR diffuse continuum dominates the UV, the recovered impulse response should correlate with the known He II, H beta and H alpha lags of roughly 2-3, 6 and 11 days; a longer campaign could measure the UV lag structure and test this.
The same analysis applied to other low-state AGN, including a re-analysis of NGC 5548 with a 15-50 keV driver, could show whether a truncated flow plus BLR reprocessing is generic rather than unique to NGC 4151.

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Editorial analysis

A structured set of objections, weighed in public.

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

Desk Editor's Note

read the letter

Short version: the paper's negative result is strong and worth taking seriously; its positive BLR-reprocessing interpretation is plausible but much less certain. The analysis is careful, the writing clear, and the authors are honest about tensions in their picture.

What's new: this is, to my knowledge, the first spectral-timing test of the lamppost reprocessing model driven by Swift BAT 15–50 keV light curves. NGC 4151 is the only AGN where BAT can be used this way during the E17 campaign. The authors build a full spectral-timing model with a hot corona, warm Comptonisation and outer disc, fit the time-averaged SED, and then predict the UVW1 variability from the observed BAT curve without re-fitting the UV data. The predicted light curve has fast peaks that are absent in the data, and the cross-correlation shows a much shorter lag and higher coherence than observed. That failure is robust to the SED decomposition (Appendix A) and to host-galaxy subtraction. It is a clean kill of the standard inner-disc picture for this source.

The soft spots are two. First, the 15–50 keV band is assumed to track the bolometric X-ray luminosity. The paper doesn't test whether the spectrum above 50 keV varies independently, and it doesn't compare with harder X-ray coverage. If the true bolometric driver were smoother than the BAT curve, the disc model might not fail as badly, and the recovered IRF could be a distortion of the wrong input. I think this is a real limitation, not a fatal one — the predicted fast variability is so strong that you'd need an implausibly smooth driver to rescue the disc — but the paper should have at least checked for spectral index variations or used NuSTAR data if available. Second, the IRF recovery in Section 4 is phenomenological, with no error bars on the recovered timescales or component fractions. The double-Gaussian is motivated by the CCF shape, but the improvement over a single Gaussian is not quantified in the final fits, and the exponentially modified Gaussian adds parameters for modest gain. The claimed 1.5–20 light-day range is consistent with BLR sizes, but without uncertainties I don't know how tightly to take it.

The paper includes a useful control in Appendix B: the same IRF recovery fails on NGC 5548 with the XRT band, which supports the idea that the BAT band is doing something real. It also discusses the apparent contradiction with line reverberation lags and gives a plausible resolution.

Net: this deserves a serious referee. I would recommend acceptance after the authors either validate or more carefully caveat the bandpass assumption, and add some error assessment to the IRF. I'd cite it if I were working on AGN variability.

Referee Report

3 major / 5 minor

Summary. This paper applies the Gardner & Done (2017) spectral-timing method to the 2016 Swift monitoring campaign of NGC 4151, using the BAT 15-50 keV light curve as the driving X-ray signal. The authors fit a truncated disc plus warm Comptonization model (agnsed) to the mean SED, inferring L/L_Edd ~ 1.4%. They then predict the UVW1 light curve from the observed BAT light curve and demonstrate that the predicted curve has far more fast variability and a shorter cross-correlation lag than the observed UVW1 curve. They next fit phenomenological linear transfer functions to the UVW1/BAT data, finding that a slowly responding component on 1.5-20 light-day timescales plus a small fast fraction describes the light curve well, and they interpret this as reprocessing by dense gas in the broad-line region. The paper concludes that optically thick material in a disc geometry is ruled out within 1.5 light days, supporting a changing-state picture in which the inner disc is replaced by a radiatively inefficient flow.

Significance. If the conclusions hold, the paper provides a strong observational constraint on accretion geometry in low-luminosity AGN: it would be the first to use a hard X-ray (BAT) driver to test disc reprocessing predictions, and it would support both the truncation of the thin disc at low Eddington ratios and the domination of the UV by diffuse BLR continuum. The manuscript is commendable for making an explicit, falsifiable prediction, for using a band less affected by absorption than the XRT, and for demonstrating robustness of the variability prediction to alternative SED decompositions in Appendix A. It also offers an energetic plausibility check for BLR reprocessing. However, the central claim rests on the unvalidated assumption that the 15-50 keV BAT band tracks the bolometric X-ray driver, and the recovered IRF parameters are presented without statistical uncertainties; both issues need to be addressed before the conclusions can be accepted at face value.

major comments (3)

[Section 3, Eq. (3) and Fig. 8] The central claim that the disc/warm-Compton reprocessing model is ruled out for radii < 1.5 light days assumes that the Swift BAT 15-50 keV light curve faithfully tracks the bolometric X-ray luminosity that drives the UV reprocessing. The paper argues that BAT is preferable to XRT because the latter is affected by variable absorption, but it does not provide any direct validation that the 15-50 keV band traces the harder X-rays where the bolometric luminosity peaks. If the flux above 50 keV has different variability amplitude or power spectrum, the predicted UVW1 light curve would change and the disc model could be reconciled with the data. The authors should either support this proxy assumption with auxiliary data (e.g., simultaneous INTEGRAL/NuSTAR coverage or a coherence analysis between BAT and XRT after correcting for absorption) or explicitly restate the rule-out as conditional on this assumption. This is load-bearing for the abstract's headline conclusion.
[Section 4, Eq. (5) and Fig. 10] The positive result - that the UVW1 is predominantly reprocessed on BLR scales of 1.5-20 light days - is obtained by fitting the UVW1 light curve with the BAT light curve as the input driver. A systematic error in the driver (for instance, if the true bolometric flux is less variable on short timescales than the 15-50 keV band) would propagate directly into the recovered IRF timescales and the inferred fast fraction. The paper does not test how the recovered IRF changes for plausible alternative drivers, so the BLR-scale conclusion is not uniquely determined. The authors should include a sensitivity analysis (e.g., a driver with a different power spectrum or with spectral-index-dependent variability) or qualify the interpretation accordingly.
[Section 4, parameter uncertainties] The IRF fits are presented without confidence intervals on the parameters fc, fs, centroids, variances, and derived size scales. The only uncertainty discussed is the systematic difference between the double-Gaussian and exponentially-modified-Gaussian forms. Since the 1.5 light-day lower limit and the 90% slow fraction are quantitative claims, a bootstrap or Monte Carlo error estimate on the recovered IRF parameters and the implied length scales is needed to support them.

minor comments (5)

[Eq. (6)] In the second term of the exponentially modified Gaussian IRF, the argument of the complementary error function uses lambda_1 sigma_2^2 where it should use lambda_2 sigma_2^2; as written the formula is internally inconsistent.
[References] The reference entries for Edelson et al. (2015) and Edelson et al. (2017) are missing the publication years, and the entry for Welsh and Horne is listed as 2016 instead of 1991.
[Section 3, first paragraph] The phrase 'to produce give an even sampling' contains a typo; it should read 'to produce an even sampling.'
[Fig. 5 caption] The caption reads 'which is more consisted with the Bentz-corrected data'; this should be 'more consistent with.'
[Section 3.1] The significance of the BAT-UVW1 correlation is not quoted for the UVW1 band itself; the text cites E17's value for UVW2. The authors should report the significance for the specific band used in the analysis.

Circularity Check

0 steps flagged · score 1.0 of 10

No significant circularity: the Section 3 UV variability prediction is genuinely out-of-sample, and the Section 4 IRF recovery is an explicitly fitted interpretation rather than a disguised input.

full rationale

The paper's central predictive step is not circular. Section 2 fits agnsed to the time-averaged SED only; the free parameters (rhot, rwarm, mdot) are determined from the mean spectrum, not from the UV variability. Section 3 then feeds the observed Swift BAT 15-50 keV light curve through equations (3)-(4) to predict the UVW1 light curve, and the predicted curve is compared to data without any UV-variability fitting. The failure of this prediction (excess fast variability, too-short lag) is a genuine, externally falsifiable result. Section 4 is an explicit fit rather than a prediction: equation (5) parameterizes fc, fs and an IRF and fits them to the UVW1 data; the recovered 1.5-20 day timescale is then compared to independent BLR size measurements (H-beta ~6 light-days, HeII 2-3 light-days), not assumed from them. The consistency of the fast fraction with the 9% direct coronal contribution is an output check, not an input constraint. Self-citations to GD17 and KD18 supply the spectral-timing machinery and the agnsed model, but the load-bearing conclusions do not reduce to those citations: the model's failure and the IRF-fit timescales are determined by the 2016 campaign data. The main weakness, that the 15-50 keV BAT band may not track the bolometric driver, is an external-validity assumption, not a circularity; it does not make the derivation equivalent to its inputs. One minor self-citation (GD17) is present but non-load-bearing, hence score 1.

Assumptions & free parameters 6 free parameters · 5 assumptions · 0 invented entities

The paper introduces no new physical entities; it reinterprets known components (inner hot flow, BLR clouds, wind). The main free parameters are the spectral fit radii and normalisation, plus the IRF parameters fitted to the UV lightcurve. The key axioms are the assumed accretion flow structure, the point-corona/flat-disc geometry, and the linear time-invariant response model.

free parameters (6)

Mass accretion rate (mdot) = log mdot = -1.86 (1.4% L_Edd)
Fitted to the time-averaged SED; sets the normalisation and determines the Eddington ratio and the transition radii.
rhot (inner hot flow radius) = 90 R_g
Free parameter in the agnsed fit; sets the inner edge of the warm Compton/disc region and hence the reprocessing timescale.
rwarm (outer warm Compton radius) = 390 R_g
Free parameter defining the extent of the warm Comptonisation region that produces the UV.
Gamma_hot (hot corona photon index) = Not stated explicitly (free in fit)
Free spectral index of the hard Compton component; value not reported in the extraction.
Host galaxy 5100 angstrom flux (two alternatives) = 1.1e-14 (Shapovalova) or 1.7e-14 (Bentz) erg/s/cm2/A
Alternative host galaxy corrections bracket the UVOT data; the UVW1 band is unaffected, but the optical band decomposition varies.
IRF parameters (fc, fs, Gaussian centroids/variances, K2, lambda1, lambda2) = fc < 0.05, fs ~ 0.9; centroids/widths shown in Figs. 9-10, numerical values not tabulated
Fitted to the UVW1 lightcurve in Section 4; these directly determine the claimed 1.5-20 light-day response scale.

assumptions (5)

domain assumption The accretion flow follows the Novikov-Thorne emissivity, with energy released in the disc and warm Compton layers, as implemented in agnsed (KD18).
The entire spectral-timing model rests on this assumed radial dissipation profile; Section 2.
domain assumption The warm Comptonisation region is a slab with Gamma_warm = 2.7 set by energy balance (Petrucci et al. 2018).
Fixes the spectral shape of the UV-emitting component; Section 2.1.
ad hoc to paper The reprocessor is a flat, optically thick disc annulus with no vertical structure, and the corona is a point-like source at height hcor = 10 R_g.
Used to compute the IRF and solid-angle reprocessing in Equations (1)-(4); the paper tests hcor = 90 and finds worse agreement, but does not explore anisotropic emission or warped discs. Sections 2 and 3, Fig. 4.
domain assumption The 15-50 keV BAT lightcurve tracks the bolometric driving luminosity.
The driving lightcurve for both the physical-model prediction and the IRF recovery; if the >50 keV spectrum varies independently, the results change. Sections 1 and 3.
ad hoc to paper The UVW1 flux is a linear, time-invariant combination of a constant, a slow BLR response, and a fast direct/reprocessed component (Equation 5).
This linear model is assumed for the IRF recovery; nonlinearities or time-dependent response would bias the derived lags. Section 4.

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Cite this review

Pith. "Pith review of Discarding the disc in a changing state AGN: the UV/X-ray relation in NGC 4151." pith.science (2026). https://pith.science/paper/T46SHA4M

@misc{pith2026190805461,
  author       = {Pith},
  title        = {Pith review of: Discarding the disc in a changing state AGN: the UV/X-ray relation in NGC 4151},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/T46SHA4M}},
  note         = {Machine review of arXiv:1908.05461}
}

abstract

Recent monitoring campaigns designed to map the accretion regime in AGN show major discrepancies with models where the optical/ultraviolet (UV) is produced by X-ray-illuminated, optically thick disc material within a few hundred gravitational radii. However, these campaigns only monitored X-rays below $10$ keV, whereas the bolometric luminosity for most of these AGN peaks above $50$ keV. We use data from the recent multiwavelength campaign by \cite{E17} on NGC 4151 - the only AGN bright enough to be monitored at higher energies with \textit{Swift} BAT. We develop a spectral-timing model with a hot corona, warm Comptonisation, and outer standard disc. This fits the time-averaged spectrum well, but completely fails to match the UV variability predicted from the X-ray lightcurve. However, it reveals that NGC 4151 had a bolometric luminosity around $1.4\%$ of the Eddington luminosity during this campaign, close to the luminosity at which AGN show a `changing-state' transition, where the broad optical lines disappear. Stellar mass black holes show a state transition at a similarly low Eddington fraction, which is broadly interpreted as the inner disc being replaced by an optically thin flow. We find that the UV lightcurve can instead be matched by reprocessing of the X-ray flux on size scales of the broad line region (BLR; $1.5-20$ light-days) and rule out there being optically thick material inwards of this, as expected if the thin disc is replaced by the flow below the inner radius of the BLR. These results emphasise the need for even longer-timescale, multiwavelength monitoring campaigns on variable AGN.

Figures

Figures reproduced from arXiv: 1908.05461 by the authors.

**Figure 1.** Mean-normalised light curves from the NGC 4151 Swift campaign in Swift BAT (panel a) and Swift UVOT UVW1 (panel b; E17). the responding material is co-spatial with the inner broad line region (BLR). We rule out there being optically thick material in a disc geometry on size scales less than 1.5 light days, as this would produce too much UV fast variability. This variability cannot be hidden by self shielding as pro… view at source ↗

**Figure 2.** Schematic of the geometry assumed here using agnsed. The blue region within rhot denotes the hard X-ray corona. The region between rwarm and rhot consists of warm, optically thick Comptonising material (green) sandwiching the thin, passive disc (grey). Hard X-rays irradiate the underlying thin disc, in turn changing the seed photon temperature and normalisation of the soft Compton emission from the warm material. Be… view at source ↗

**Figure 3.** Fit to data with the model hostpol + phabs * zredden * [pcfabs * pcfabs * (rdblur * pexmon + agnsed1) + agnsed2 + mekal + mekal]. The soft and hard Compton components are denoted by the solid green and cyan lines respectively, while the outer disc component is shown by the solid red line. The pink solid line denotes the distant reflection component. Constant components (stars at optical/UV from an Sb template, and h… view at source ↗

Figures from the paper (8 more)

**Figure 4.** Figure 4: , where we compare the canonical fit (red, solid line) with one where all parameters are the same except using hcor = rhot = 90 (black, solid line). Clearly, increasing the scale height of the corona increases the fraction of reprocessing in the optical/UV due to the l…

**Figure 5.** Figure 5: Comparison of HST STIS data taken in February 1998 and May 2000, with the 2016 Swift UVOT data which has here been corrected for host galaxy emission. We show HST STIS data taken on 1998-02-10 (blue dots; ObsIDs: O42302070, O42302080, O423020A0) and HST STIS data taken…

**Figure 6.** Figure 6: Model spectrum: Cyan line denotes the total hard Compton emission from the corona, which illuminates the disc. The solid green line shows the total soft-Compton emission from the warm material on the disc, which reprocesses all thermal emission from the underlying thin…

**Figure 7.** Figure 7: Top panel: Re-binned and interpolated Swift BAT light curve. Bottom panel: Re-binned and interpolated UVW1 light curve in blue. The predicted UVW1 light curve resulting from the model assuming disc illumination driving warm Comptonisation is denoted in red. The lack of…

**Figure 8.** Figure 8: Normalised cross-correlation functions between the Swift BAT light curve and UVW1 observed light curve (blue), and the Swift BAT light curve and modeled UVW1 light curve (red). simple reprocessing/warm Comptonisation model where the Comptonisation takes place between 9…

**Figure 9.** Figure 9: Modeled UVW1 light curve using phenomenological impulse responses to the BAT curve. Panel (a): Red, solid line denotes the impulse response function used to fit the UVW1 light curve, composed of a sum of two Gaussians. The dashed lines denote the two constituent Gaussi…

**Figure 10.** Figure 10: Modeled UVW1 light curve using exponentiallyskewed Gaussian response to the BAT curve input, for the entirety of the pointed campaign. Panel (a): IRF used to fit the UVW1 light curve, with functional form in equation (6). Panel (b.i): Rebinned and interpolated Swift…

**Figure 11.** Figure 11: The geometry we propose to explain both the observed SED and derived impulse response functions. The blue zones denote the radiatively inefficient accretion flow which emits strongly in the hard X-rays. The red/white circles denote the broad-line region clumps which r…

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Works this paper leans on

73 extracted references · 72 canonical work pages

[1]

Almeyda T., Robinson A.,Richmond M., Vazquez B., Nikutta R., 2017, ApJ, 841, 1

work page 2017
[2]

& Cohen R.D., 1983, ApJ, 271, 564

Antonucci R.R.J. & Cohen R.D., 1983, ApJ, 271, 564

work page 1983
[3]

Ar\' e valo P., Uttley P., Lira P., Breedt E., McHardy I.M., Churazov E., 2009, MNRAS, 397, 2004

work page 2009
[4]

Arnaud K., Borkowski K.J., Harrington J.P., 1996, ApJ, 462, L75

work page 1996
[5]

Arnaud M., Raymond J., 1992, ApJ, 398, 394

work page 1992
[6]

Baron D., Stern J., Poznanski D., Netzer H., 2016, ApJ, 832 (1), 8

work page 2016
[7]

Barvainis R., 1987, ApJ, 320, 537

work page 1987
[8]

et al., 2017, A&A, 603, A50

Beuchert T., Markowitz A.G., Dauser T. et al., 2017, A&A, 603, A50

work page 2017

Show all 73 references

[9]

et al., 2006, ApJ, 651, 775

Bentz M.C., Denney K.D., Cackett E.M. et al., 2006, ApJ, 651, 775

2006
[10]

et al., 2013, ApJ, 767 (2), 149

Bentz M.C., Denney K.D.,Grier C.J. et al., 2013, ApJ, 767 (2), 149

2013
[11]

& Paltani S., 2016, A&A, 588, A70

Boissay R., Ricci C. & Paltani S., 2016, A&A, 588, A70

2016
[12]

et al., 2018, MNRAS, 475 (2), 2306

Buisson D.J.K., Lohfink A.M., Alston W.N. et al., 2018, MNRAS, 475 (2), 2306

2018
[13]

Chelouche D., Nu\ n ez F.P., Kaspi, S., 2018, Nat. Astron

2018
[14]

Davis S.W., Woo J.-H., Blaes O.M, 2007, ApJ, 668 (2), 682

2007
[15]

et al., 2018, ApJ, 866, 133

De Rosa G., Fausnaugh M.M., Grier C.J. et al., 2018, ApJ, 866, 133

2018
[16]

et al., 2019, ApJ, 877 (2), 119

Dehghanian M., Ferland G.J., Kriss G.A. et al., 2019, ApJ, 877 (2), 119

2019
[17]

et al., 2019, ApJL, 882, 2

Dehghanian M., Ferland G.J., Peterson B.M. et al., 2019, ApJL, 882, 2

2019
[18]

Done C., Gierli\' n ski M., Kubota A., 2007, A&ARv, 15, 1

2007
[19]

Done C., Davis S.W., Jin C., Blaes O., Ward M., 2012, MNRAS, 420, 1848

2012
[20]

et al., ApJ, 806, 129

Edelson R., Gelbord K., Horne K. et al., ApJ, 806, 129
[21]

et al., ApJ, 840, 41 (E17)

Edelson R., Gelbord K., Cackett E. et al., ApJ, 840, 41 (E17)
[22]

et al., 2018, MNRAS, 472 (3), 3492

Ezhikode S.H., Gandhi P., Done C. et al., 2018, MNRAS, 472 (3), 3492

2018
[23]

Fabian A.C., Rees M.J., Stella L., White N.E., 1989, MNRAS, 238, 729

1989
[24]

Frank J., King A., Raine D., 2002, Accretion Power in Astrophysics: Third Edition, Cambridge University Press, pp. 83-84

2002
[25]

Galeev A., Rosner R., Vaiana G., 1979, ApJ, 229, 318

1979
[26]

et al., 2019, ApJ, 871, 88

Garc \' a J.A., Kara E., Walton D. et al., 2019, ApJ, 871, 88

2019
[27]

Gardner E., Done C., 2017, MNRAS, 470, 3591 (GD17)

2017
[28]

Gierli \'n ski M., Done C., 2004, MNRAS, 349, L7

2004
[29]

Haardt F., Maraschi L., 1993, ApJ, 413, 507

1993
[30]

Inoue Y., Doi A., 2018, ApJ, 869 (2), 114

2018
[31]

Jin C., Ward M., Done C., Gelbord J., 2012, MNRAS 420, 1825

2012
[32]

et al., 2000, ApJ, 528, 260

Kaiser M.E., Bradley L.D., Hutchings J.B. et al., 2000, ApJ, 528, 260

2000
[33]

et al., 2015, ApJ, 806, 149

Keck M.L., Brenneman L.W., Ballantyne D.R. et al., 2015, ApJ, 806, 149

2015
[34]

et al., ApJ Letts., 2013, 775 (2), L36

Kishimoto M., H\" o nig S.F., Antonucci R. et al., ApJ Letts., 2013, 775 (2), L36

2013
[35]

Korista K.T., Goad M.R., 2001, ApJ, 553, 695

2001
[36]

(KD18) Kubota A., Done C., 2018, MNRAS, 480, 1247

2018
[37]

Laor A., Davis S.W., 2014, MNRAS, 438 (4), 3042

2014
[38]

Lawrence A., 2018, Nature Astronomy, 2, 102-103

2018
[39]

Lawther D., Goad M.R., Korista K.T., Ulrich O., Vestergaard M., 2018, MNRAS, 481 (1), 533

2018
[40]

Lubi\' n ski P., Zdziarski A.A., Walter R., Paltani S., Beckmann V., Soldi S., Ferrigno C., Courvoisier T.J.-L., 2010, MNRAS, 408 (3), 1851

2010
[41]

Magdziarz P., Blaes O.M., Zdziarski A.A., Johnson W.N., Smith D.A., 1998, MNRAS, 301, 179

1998
[42]

et al., 2014, MNRAS, 439, 3016

Matt G., Marinucci A., Guainazzi M. et al., 2014, MNRAS, 439, 3016

2014
[43]

et al., 2011, A&A, 534, A39

Mehdipour M., Branduardi-Raymont G., Kaastra J.S. et al., 2011, A&A, 534, A39

2011
[44]

et al., 2015, A&A, 575, A22

Mehdipour M., Kaastra J.S., Kriss G.A. et al., 2015, A&A, 575, A22

2015
[45]

et al., 2016, A&A, 588, A139

Mehdipour M., Kaastra J.S., Kriss G.A. et al., 2016, A&A, 588, A139

2016
[46]

Mewe R., Gronenschild E.H.B.M., van den Oord, G.H.J., 1985, A&A Suppl., 62, 197

1985
[47]

et al., 2017, ApJ, 865 (2), 97

Miller J.M., Cackett E., Zoghbi A. et al., 2017, ApJ, 865 (2), 97

2017
[48]

Nandra K., O'Neill P.M., George I.M., Reeves J.N., 2007, MNRAS, 382, 194

2007
[49]

Noda H., Done C., 2018, MNRAS, 480, 3898

2018
[50]

Novikov I.D., Thorne K.S., 1973, blho.conf, 343

1973
[51]

Oknyansky V.L., Metlova N.V., Taranova O.G., Shenavrin V.I., Artamonov B.P., Gaskell C.M., Guo Di-Fu, 2014, Odessa Astronomical Publications, 27, 47

2014
[52]

et al., 2017, ApJ, 837, 131

Pei L., Fausnaugh M.M., Barth A.J. et al., 2017, ApJ, 837, 131

2017
[53]

Penston M.V., Perez E., 1984, MNRAS, 211, 33

1984
[54]

et al., 2013, A&A, 549, A73

Petrucci P.-O., Paltani S., Malzac J. et al., 2013, A&A, 549, A73

2013
[55]

Petrucci P.O., Ursini F., De Rosa A., Bianchi S., Cappi M., Matt G., Dadina M., Malzac J., 2018, A&A, 611, A59

2018
[56]

Peterson B.M., Cota S.A., 1988, ApJ, 330, 111

1988
[57]

Peterson B.M., Horne K., 2004, Astronomische Nachrichten, 325, 248

2004
[58]

Porquet D., Reeves J.N., O'Brien P., Brinkmann W., 2004, A&A, 422, 85

2004
[59]

et al., 2018, A&A, 609, A42

Porquet D., Reeves J.N., Matt G. et al., 2018, A&A, 609, A42

2018
[60]

et al., 2003, ApJ, 126 (3), 1131

Richards G.T., Hall P.B., Vanden Berk D.E. et al., 2003, ApJ, 126 (3), 1131

2003
[61]

et al., 2019, submitted, arXiv:1903.02553

Ruan J.J., Anderson S.F., Eracleous M. et al., 2019, submitted, arXiv:1903.02553

2019 arXiv
[62]

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

1973
[63]

et al., 2008, A&A, 486, 99

Shapovalova A.I., Popovi \'c L.C., Collin S. et al., 2008, A&A, 486, 99

2008
[64]

Shu X.W., Yaqoob T., Wang J.X., 2010, ApJ Suppl., 187, 581

2010
[65]

Shull M.J., Stevans M., Danforth C.W., 2012, ApJ, 752 (2), 162

2012
[66]

Telfer R.C., Zheng W., Kriss G.A., Davidsen A.F., 2002, ApJ, 565 (2), 772

2002
[67]

et al., 1984, MNRAS, 206 221

Ulrich M.H., Boksenber A., Bromage G.E. et al., 1984, MNRAS, 206 221

1984
[68]

Veledina A., 2016, ApJ, 832, 181

2016
[69]

Welsh W.F., Horne K., 2016, ApJ, 379, 586

2016
[70]

& Narayan R., 2003, ApJ, 598 (1), 301

Yuan F., Quataert E. & Narayan R., 2003, ApJ, 598 (1), 301

2003
[71]

Zheng W., Kriss G.A., Telfer R.C, Grimes J.P., Davidsen A.F., 1997, ApJ, 475 (2), 469

1997
[72]

Zoghbi A., Miller J., Cackett E., 2019, ApJ, 884, 26

2019
[73]

Zy \.c ki P.T., Done C., Smith D.A., 1999, MNRAS, 305, 231

1999

Pith tools

Reviewed August 14, 2026 · model on record in the stance chip above.

[1] [1]

Almeyda T., Robinson A.,Richmond M., Vazquez B., Nikutta R., 2017, ApJ, 841, 1

work page 2017

[2] [2]

& Cohen R.D., 1983, ApJ, 271, 564

Antonucci R.R.J. & Cohen R.D., 1983, ApJ, 271, 564

work page 1983

[3] [3]

Ar\' e valo P., Uttley P., Lira P., Breedt E., McHardy I.M., Churazov E., 2009, MNRAS, 397, 2004

work page 2009

[4] [4]

Arnaud K., Borkowski K.J., Harrington J.P., 1996, ApJ, 462, L75

work page 1996

[5] [5]

Arnaud M., Raymond J., 1992, ApJ, 398, 394

work page 1992

[6] [6]

Baron D., Stern J., Poznanski D., Netzer H., 2016, ApJ, 832 (1), 8

work page 2016

[7] [7]

Barvainis R., 1987, ApJ, 320, 537

work page 1987

[8] [8]

et al., 2017, A&A, 603, A50

Beuchert T., Markowitz A.G., Dauser T. et al., 2017, A&A, 603, A50

work page 2017