Pith. sign in

REVIEW 3 major objections 5 minor 112 references

Reverberation Mapping of Two Variable Active Galactic Nuclei: Probing the Distinct Characteristics of the Inner and Outer Broad-line Regions

T0 review · 3 major / 5 minor · reviewed 2026-08-11 · deepseek-v4-flash

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

Pith's one-line read Multiline reverberation mapping of two active galactic nuclei claims the broad-line region is radially stratified into regions with different kinematics—outflow in one inner region, inflow in another outer region—and that breathing versus…

desk verdict Real new RM data for two AGNs, but the outflow/inflow claims rest on velocity-resolved lag asymmetries shown without uncertainties, so the kinematics are not yet nailed down. read the letter →

arxiv 2412.02204 v1 pith:4YJKLURC submitted 2024-12-03 astro-ph.GA

Hai-Cheng Feng , Sha-Sha Li , J. M. Bai , H. T. Liu , Kai-Xing Lu , Yu-Xuan Pang , Mouyuan Sun , Jian-Guo Wang
show 3 more authors
Yerong Xu Yang-Wei Zhang Shuying Zhou
This is my paper · ORCID
classification astro-ph.GA
keywords activegalacticnucleireverberationmappingbroad-lineregionvelocity-resolvedtimelagsSeyfertgalaxiesionizationstratificationbreathingeffectsupermassiveblackholes
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 multiline reverberation-mapping observations of two active galactic nuclei, KUG 1141+371 and UGC 3374, and uses them to argue that the broad-line region is not a single kinematic zone. By measuring time delays of five broad emission lines—Hα, Hβ, Hγ, He I, and He II—relative to the continuum, the authors find clear radial ionization stratification, with different lines tracing gas at different distances from the supermassive black hole. Assuming that velocity-resolved lags reflect gas kinematics, the velocity dependence of those delays leads them to infer that in KUG 1141+371 the inner BLR shows outflow while the outer region is virialized, while in UGC 3374 the inner region is virialized and the outer region shows inflow. They also report "breathing" in the outer BLR and "anti-breathing" in the inner BLR of both objects. If correct, these results imply that single-line reverberation mapping can miss much of the BLR structure and may explain some of the scatter in black hole mass estimates.

What carries the argument

The mechanism is velocity-resolved reverberation mapping: each broad emission line is divided into velocity bins, light curves are extracted per bin, and each is cross-correlated with the continuum light curve to obtain a time delay as a function of line-of-sight velocity. Different broad lines trace different ionization zones, so comparing their velocity-delay profiles probes the inner versus outer BLR. The interpretive recipes are that symmetric delays with shorter lags at high velocity mean virialized motion, longer lags on the redshifted side mean outflow, and longer lags on the blueshifted side mean inflow; "breathing" and "anti-breathing" refer to whether line width decreases or increases as line flux rises.

What would settle it

A velocity-delay map of Hβ in UGC 3374 built from denser sampling that places the blue-shifted responding gas at the same radius as the red-shifted gas—or that shows the asymmetry as a bright off-center cloud—would falsify the inflow interpretation. Simultaneous UV and optical monitoring that finds a large UV-optical lag during the bright state would instead show that the apparent Hβ anti-breathing is an artifact rather than an intrinsic BLR property.

Watch

Extended reading notes

Core claim

The central discovery is that the kinematics of the broad-line region are radially stratified in both objects. In KUG 1141+371, velocity-resolved lags of Hβ, Hγ, He I, and He II—lines that trace the inner BLR—are longer on the red side than the blue side, which the paper interprets as outflowing gas, while Hα from the outer region gives a symmetric lag profile consistent with virialized motion. In UGC 3374 the pattern is inverted: the inner lines give symmetric, virialized lags, while Hα shows longer lags on the blue side, interpreted as inflow. In both AGNs, the outer Hα line follows normal "breathing" (line width decreasing as flux increases), while the inner He I line shows "anti-breathing" (line width increasing with flux), with Hβ falling in between. The paper treats these patterns as evidence that the inner and outer BLR have different physical conditions and perhaps different origins, and that the apparently rapid changes in velocity-resolved RM signatures seen in other AGNs may be a consequence of the line-emitting region shifting between these zones as luminosity changes.

Load-bearing premise

The outflow and inflow conclusions rest on the assumption that velocity-resolved lag asymmetries trace bulk radial gas motion in a roughly symmetric broad-line region, rather than arising from an asymmetric spatial distribution of the line-emitting gas.

Editorial extensions

If this is right

  • Single-line reverberation mapping, especially of Hβ alone, underestimates the dynamical richness of the BLR; multiline campaigns are needed to separate inner and outer zones.
  • Black hole masses derived from different lines, or from the same line at different epochs, can disagree because each line samples a different kinematic zone, which contributes to scatter in RM mass estimates.
  • Rapid changes in velocity-resolved RM signatures do not require rapid physical restructuring of the BLR; they can arise as the responding region shifts between inner and outer zones with luminosity.
  • The coexistence of breathing and anti-breathing in the same AGN means the BLR cannot be described by a single radius-luminosity or width-flux relation.
  • Observed lags shorter than the R-L relation predictions in both objects suggest that intrinsic BLR properties beyond accretion rate influence the relation.

Reading between the lines

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

  • A testable extension would be to compare these velocity-delay profiles with full velocity-delay maps: if the red/blue asymmetries reflect stable spatial asymmetries rather than net radial motion, the maps would show off-center bright regions with the same lag structure.
  • The anti-breathing interpretation is not fully settled by the data; simultaneous UV and optical monitoring could determine whether the UV-optical lag grew during the bright state, in which case the true Hβ radius may not have shrunk.
  • If the stratification is a general property, future dense-cadence campaigns ought to find a fixed ordering—He II and He I responding first with anti-breathing, Hα last with breathing—across many AGNs.
Share X Bluesky LinkedIn Reddit HN

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. This paper presents multiline reverberation-mapping (RM) observations of two active galactic nuclei, KUG 1141+371 and UGC 3374, using the Lijiang 2.4 m telescope. The authors measure time lags for Hα, Hβ, Hγ, He I, and He II, find evidence for radial ionization stratification, and perform velocity-resolved RM for each line. Based on the shape of the velocity-resolved centroid lags, they conclude that in KUG 1141+371 the inner BLR shows outflow signatures while the outer region is virialized, and in UGC 3374 the inner BLR is virialized while the outer region shows inflow. The paper also reports a 'breathing' to 'anti-breathing' transition between outer and inner BLR regions in both objects. These claims are discussed in the context of BLR formation models and the scatter in black hole mass estimates.

Significance. The paper provides a useful multiline RM dataset for two relatively understudied AGNs, with machine-readable light curves (Tables 1 and 2), integrated lags for five emission lines, and velocity-resolved lag profiles. The detection of radial ionization stratification is consistent with photoionization expectations and increases the small sample of AGNs with multiline RM. The principal kinematic claims—inner outflow versus virialized outer BLR in KUG 1141+371, and virialized inner versus inflowing outer BLR in UGC 3374—are intriguing but rest on velocity-resolved asymmetries whose significance is not quantified. The reported breathing-to-anti-breathing transition is securely detected in only one of the two objects. If the asymmetries are confirmed with proper uncertainties, the results would support stratified BLR kinematic models and help explain scatter in black hole mass estimates; in the current form, the central kinematic conclusions are not yet established to the claimed confidence. The paper's use of publicly available fitting codes (DASpec, PyCALI, linmix) is a strength for reproducibility.

major comments (3)
  1. [§4.3 and Figures 5, 6] The velocity-resolved lags shown in Figures 5 and 6 are presented without per-bin uncertainties; the numerical values printed in each bin are rmax correlation coefficients, not error bars. The reported red-side versus blue-side lag asymmetries that drive the outflow/inflow conclusions are therefore not quantified. Please provide per-bin lag uncertainties (e.g., via Monte Carlo or bootstrap methods) and assess the significance of each asymmetry. This is especially important because several integrated lags in Table 4 (e.g., He I and He II in KUG 1141+371 and He II in UGC 3374) are consistent with zero within their uncertainties.
  2. [§3.1 and §5.2.1] The broad Hγ profile is explicitly constrained to be identical in shape to the broad Hβ profile (§3.1). Consequently, the Hγ light curve and its velocity-resolved lags are not independent tracers of the inner BLR. Using Hγ as independent evidence for the inner outflow in KUG 1141+371 (Section 5.2.1) is therefore circular. Please either drop Hγ from the kinematic evidence or demonstrate quantitatively that its velocity-resolved lags are not trivially determined by the Hβ constraint.
  3. [§5.3 and Figure 9] The claim that 'He I exhibits a clear anti-breathing' in both AGNs is not supported by the displayed fits. For KUG 1141+371, the linmix slope for He I is β = 1.18 ± 1.36, which is consistent with no correlation at the 1σ level, while only UGC 3374 shows a significant positive slope (β = 0.28 ± 0.04). The statement that Hβ falls between the two extremes is also inaccurate for KUG, where β = −0.14 ± 0.07, i.e., on the breathing side. Please revise the anti-breathing conclusion and report the significance of each slope.
minor comments (5)
  1. [§5.1] The text refers to 'KUG 1141+37' in the first paragraph of Section 5.1; this should be 'KUG 1141+371'.
  2. [Abstract] The phrase 'highlighting importance of long-term' should read 'highlighting the importance of long-term'.
  3. [§4.3] The sentence 'we divided each emission line was into several velocity bins' contains a grammatical error; it should be 'we divided each emission line into several velocity bins'.
  4. [§5.1] In Section 5.1, 'to establish a reliable relationship' is written as 'to establish a an reliable' in the draft; please correct the article.
  5. [Figures 5, 6] In the captions of Figures 5 and 6, please clarify that the gray band in the top panel marks the error range of the mean delay, not the per-bin delays, and state where the per-bin uncertainties (if available) are shown.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: velocity-resolved lags are direct CCF measurements; the kinematic interpretation is an explicit, flagged assumption, not a fitted or self-referential output.

full rationale

The paper's central chain—spectral-decomposition light curves, interpolated CCF/CCCD lags, and velocity-bin centroid lags—is empirical and self-contained, and the outflow/inflow/virialized conclusions are not outputs of a fit to those conclusions. The abstract and Section 5.2.1 state the interpretive premise ('Assuming that velocity-resolved lags reflect the kinematics of BLR'), and Sections 5.2.1 and 5.2.2 explicitly acknowledge that asymmetric BLR geometry can mimic the same lag asymmetries, citing Li et al. (2024). That overlapping-author citation is used as a caveat that weakens the kinematic reading, not as the load-bearing justification that forces it, so it does not make the claim circular. The black hole masses use an external virial factor from Woo et al. (2015), and the R-L comparisons use external relations from Bentz et al. (2013) and Du & Wang (2019); neither is fitted to the claimed stratification. The absence of per-velocity-bin lag uncertainties is a statistical robustness concern rather than a circularity, and no equation in the paper reduces a prediction to a fitted input.

Assumptions & free parameters 7 free parameters · 6 assumptions · 0 invented entities

The kinematic and breathing claims do not require unseen parameters or new physical entities. The main inputs are observed light curves, the spectral decomposition choices, the externally calibrated virial factor for masses, and the fitted FWHM-flux slopes that support the breathing/anti-breathing interpretation.

free parameters (7)
  • Fitted slope beta for H alpha, KUG 1141+371 = -0.22 +/- 0.07
    Slope of log FWHM versus log line flux fitted with linmix; negative value supports the breathing interpretation for the outer BLR.
  • Fitted slope beta for H beta, KUG 1141+371 = -0.14 +/- 0.07
    Intermediate breathing behavior claimed for H beta between outer and inner regions.
  • Fitted slope beta for He I, KUG 1141+371 = 1.18 +/- 1.36
    Reported as anti-breathing evidence but the slope is consistent with zero, making the claim statistically weak.
  • Fitted slope beta for H alpha, UGC 3374 = -0.32 +/- 0.02
    Supports breathing behavior for the outer BLR.
  • Fitted slope beta for H beta, UGC 3374 = -0.02 +/- 0.05
    No significant breathing or anti-breathing for H beta in UGC 3374.
  • Fitted slope beta for He I, UGC 3374 = 0.28 +/- 0.04
    Positive slope supports the anti-breathing interpretation for the inner BLR.
  • Virial factor f = 4.47 +/- 1.25
    Adopted from Woo et al. (2015) to convert line widths and lags into black hole masses; not used for the kinematic stratification conclusions.
assumptions (6)
  • domain assumption Linearity and stationarity of the BLR response: continuum variations drive line variations through a linear, time-invariant transfer function.
    Foundation of the reverberation mapping method; invoked in Section 4.1 when interpreting CCF centroids as lags.
  • domain assumption Velocity-resolved lags can be interpreted as BLR kinematics under a symmetric geometry.
    Section 5.2.1 states that RM studies generally attribute lag profiles to kinematic regimes assuming symmetry; the authors acknowledge Li et al. (2024) for the alternative asymmetric geometry.
  • domain assumption Each emission line traces a specific radial zone of the BLR (ionization stratification).
    Used in Section 5.2 to assign H alpha to the outer BLR and He II to the inner BLR, following the LOC model.
  • domain assumption Minor reverberation effects within individual velocity bins are negligible.
    Section 4.3 explicitly states this when velocity-resolved light curves are extracted from the same spectra.
  • ad hoc to paper The broad H gamma profile can be tied to the broad H beta profile.
    Section 3.1 states H gamma is blended with [O III] and constrained to have the same profile as broad H beta, reducing its independence as a kinematic tracer.
  • domain assumption Single Gaussian profiles adequately represent broad emission lines for the purpose of light-curve extraction.
    Section 3.1 reports that double-Gaussian and fourth-order Gauss-Hermite models give consistent results, so the simpler model is adopted.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Reverberation Mapping of Two Variable Active Galactic Nuclei: Probing the Distinct Characteristics of the Inner and Outer Broad-line Regions." pith.science (2026). https://pith.science/paper/4YJKLURC

@misc{pith2026241202204,
  author       = {Pith},
  title        = {Pith review of: Reverberation Mapping of Two Variable Active Galactic Nuclei: Probing the Distinct Characteristics of the Inner and Outer Broad-line Regions},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/4YJKLURC}},
  note         = {Machine review of arXiv:2412.02204}
}
read the original abstract

Current reverberation mapping (RM) studies primarily focus on single emission lines, particularly the \hb\ line, which may not fully reveal the geometry and kinematic properties of the broad-line region (BLR). To overcome this limitation, we conducted multiline RM observations on two highly variable active galactic nuclei (AGNs), KUG 1141+371 and UGC 3374, using the Lijiang 2.4 m telescope. Our goal was to investigate the detailed structure of different regions within the BLR. We measured the time lags of multiple broad emission lines (\ha, \hb, \hg, \hei, and \heii) and found clear evidence of radial ionization stratification in the BLRs of both AGNs. Velocity-resolved RM analysis revealed distinct geometry and kinematics between the inner and outer regions of the BLRs. Assuming that velocity-resolved lags reflect the kinematics of BLR, our observations indicate that: (1) in KUG 1141+371, the inner BLR exhibits outflow signatures, while the outer region is consistent with virialized motion; (2) in UGC 3374, the inner region displays virial motion, while the outer region shows inflow. Furthermore, we detected ``breathing" behavior in the outer BLR regions of both AGN, while the inner BLR regions show ``anti-breathing", which may be linked to intrinsic BLR properties. We discuss these findings in the context of various BLR formation models, highlighting importance of long-term, multiline RM campaigns in understanding of BLR structure and evolution. Additionally, our results suggest that the observed stratification in BLR geometry and kinematics may contribute to the scatter in black hole mass estimates and the rapid changes in velocity-resolved RM signatures reported in recent studies.

Figures

Figures reproduced from arXiv: 2412.02204 by the authors.

Figure 1
Figure 1. Long-term light curves of KUG 1141+371 and UGC 3374. These were collected from multiple sources, including ASAS-SN, ZTF, and our observations at Lijiang. These light curves were calibrated using PyCALI. in the V and g bands from ASAS-SN Sky Patrol V2.02 , which performs aperture photometry following the method￾ology described by Hart et al. (2023). 2 http://asas-sn.ifa.hawaii.edu/skypatrol/ ZTF3 employs a 48inch tel… view at source ↗
Figure 2
Figure 2. Photometric light curves. The left-top panel displays the light curves of KUG 1141+371 and its comparison star, while the right-top panel shows the light curves for UGC 3374 and its comparison star. The dots represent the light curves of the targets, and the upward triangles depict the light curves of comparison stars. Blue represents the B band and red corresponds to the R band. In the bottom of each panel, is the … view at source ↗
Figure 3
Figure 3. Spectral fitting schematic of the mean spectrum for KUG 1141+371 (left) and UGC 3374 (right). Each subplot contains two panels. In the top panel, black line represents the original spectrum, cyan lines depict broad He I and He II lines, magenta lines illustrate broad Balmer lines, orange lines indicate narrow lines, blue line represents the AGN power law, gray line corresponds to the host template, green line shows … view at source ↗
Figures from the paper (8 more)
Figure 4
Figure 4. Figure 4: Light curves and CCF results for KUG 1141+371 (left) and UGC 3374 (right). Panels (a)-(f) represent light curves for photometry, Hα, Hβ, Hγ, He I and He II. The units for emission lines are 10−14erg s−1 cm−2 for KUG 1141+371 and 10−13erg s−1 cm−2 for UGC 3374, respecti…
Figure 5
Figure 5. Figure 5: Velocity-resolved time delays for KUG 1141+371. Each subplot presents the results for different emission lines and is divided into two sections. The top panel shows the time delay for each velocity bin. The horizontal dotted line represents the mean delay for each emis…
Figure 6
Figure 6. Figure 6: Same as [PITH_FULL_IMAGE:figures/full_fig_p010_6.png]
Figure 7
Figure 7. Figure 7: RHβ - L5100 relation. The gray points correspond to RM results from Du & Wang (2019). The blue star represents KUG 1141+371, while the red and green squares represent Hβ re￾sults of UGC 3374 obtained from this work and Fausnaugh et al. (2017), respectively. The black d…
Figure 8
Figure 8. Figure 8: The Eigenvector 1 plane of AGNs. The dots represent the sample from Du & Wang (2019), color-coded by log M˙ . The green square marks the result of UGC 3374 from Fausnaugh et al. (2017). The blue stars and red squares display the results derived from the individual spec…
Figure 9
Figure 9. Figure 9: The relation between the emission line flux and its FWHM. Each panel presents the results for Hα, Hβ, and He I for KUG 1141+371 and UGC 3374, respectively. Black dots indicate the best-fit results derived from individual spectra, while the red line represents the best …
Figure 10
Figure 10. Figure 10: Comparison of flux measurements obtained from individual spectra fitting and bootstrap resampling. “Fitted Flux” refers to the flux determined from the original spectral fitting, while “Bootstrap Flux” represents the flux estimated through the bootstrap resampling met…
Figure 11
Figure 11. Figure 11: Same as [PITH_FULL_IMAGE:figures/full_fig_p016_11.png]

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

112 extracted references · 8 canonical work pages

  1. [1]

    2 G [ ]Bd' Uܣ9 <q

    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...

    2019

  2. [2]

    doi:10.1038/s41586-024-07053-4

    Abuter, R., Allouche, F., Amorim, A., et al.\ 2024, , 627, 281. doi:10.1038/s41586-024-07053-4

    doi:10.1038/s41586-024-07053-4 2024

  3. [3]

    doi:10.1086/309827

    Baldwin, J., Ferland, G., Korista, K., et al.\ 1995, , 455, L119. doi:10.1086/309827

    doi:10.1086/309827 1995

  4. [4]

    S., Du, P., et al.\ 2022, , 262, 14

    Bao, D.-W., Brotherton, M. S., Du, P., et al.\ 2022, , 262, 14. doi:10.3847/1538-4365/ac7beb

    doi:10.3847/1538-4365/ac7beb 2022

  5. [5]

    J., Bennert, V

    Barth, A. J., Bennert, V. N., Canalizo, G., et al.\ 2015, , 217, 26. doi:10.1088/0067-0049/217/2/26

    doi:10.1088/0067-0049/217/2/26 2015

  6. [6]

    C., Kulkarni, S

    Bellm, E. C., Kulkarni, S. R., Graham, M. J., et al.\ 2019, , 131, 018002. doi:10.1088/1538-3873/aaecbe

    doi:10.1088/1538-3873/aaecbe 2019

  7. [7]

    C., Denney, K

    Bentz, M. C., Denney, K. D., Grier, C. J., et al.\ 2013, , 767, 149. doi:10.1088/0004-637X/767/2/149

    doi:10.1088/0004-637x/767/2/149 2013

  8. [8]

    C., Walsh, J

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

    doi:10.1088/0004-637x/705/1/199 2009

Show all 112 references
  1. [9]

    C., Walsh, J

    Bentz, M. C., Walsh, J. L., Barth, A. J., et al.\ 2010, , 716, 993. doi:10.1088/0004-637X/716/2/993

    2010 doi

  2. [10]

    Blandford, R. D. & McKee, C. F.\ 1982, , 255, 419. doi:10.1086/159843

    1982 doi

  3. [11]

    doi:10.3389/fspas.2018.00003

    Bon, N., Bon, E., & Marziani, P.\ 2018, Frontiers in Astronomy and Space Sciences, 5, 3. doi:10.3389/fspas.2018.00003

    2018

  4. [12]

    Boroson, T. A. & Green, R. F.\ 1992, , 80, 109. doi:10.1086/191661

    1992 doi

  5. [13]

    & Charlot, S.\ 2003, , 344, 1000

    Bruzual, G. & Charlot, S.\ 2003, , 344, 1000. doi:10.1046/j.1365-8711.2003.06897.x

    2003

  6. [14]

    Cackett, E. M. & Horne, K.\ 2006, , 365, 1180. doi:10.1111/j.1365-2966.2005.09795.x

    2006

  7. [15]

    doi:10.1093/mnras/stad051

    Chen, Y.-J., Bao, D.-W., Zhai, S., et al.\ 2023, , 520, 1807. doi:10.1093/mnras/stad051

    2023 doi

  8. [16]

    & Hryniewicz, K.\ 2011, , 525, L8

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

    2011 doi

  9. [17]

    & Netzer, H.\ 1979, Reviews of Modern Physics, 51, 715

    Davidson, K. & Netzer, H.\ 1979, Reviews of Modern Physics, 51, 715. doi:10.1103/RevModPhys.51.715

    1979 doi

  10. [18]

    M., Grier, C

    De Rosa, G., Fausnaugh, M. M., Grier, C. J., et al.\ 2018, , 866, 133. doi:10.3847/1538-4357/aadd11

    2018 doi

  11. [19]

    D., Peterson, B

    Denney, K. D., Peterson, B. M., Pogge, R. W., et al.\ 2009, , 704, L80. doi:10.1088/0004-637X/704/2/L80

    2009 doi

  12. [20]

    Du, P.\ 2024, DASpec: A code for spectral decomposition of active galactic nuclei, v0.8, Zenodo, doi:10.5281/zenodo.12578528

    2024 doi

  13. [21]

    doi:10.3847/1538-4357/aaae6b

    Du, P., Zhang, Z.-X., Wang, K., et al.\ 2018, , 856, 6. doi:10.3847/1538-4357/aaae6b

    2018 doi

  14. [22]

    & Wang, J.-M.\ 2019, , 886, 42

    Du, P. & Wang, J.-M.\ 2019, , 886, 42. doi:10.3847/1538-4357/ab4908

    2019 doi

  15. [23]

    & Wang, J.-M.\ 2023, , 671, A26

    Du, P. & Wang, J.-M.\ 2023, , 671, A26. doi:10.1051/0004-6361/202244780

    2023 doi

  16. [24]

    J., Pounds, K., et al.\ 2002, , 568, 610

    Edelson, R., Turner, T. J., Pounds, K., et al.\ 2002, , 568, 610. doi:10.1086/323779

    2002 doi

  17. [25]

    T., Blandford, R

    Emmering, R. T., Blandford, R. D., & Shlosman, I.\ 1992, , 385, 460. doi:10.1086/170955

    1992 doi

  18. [26]

    M., Grier, C

    Fausnaugh, M. M., Grier, C. J., Bentz, M. C., et al.\ 2017, , 840, 97. doi:10.3847/1538-4357/aa6d52

    2017 doi

  19. [27]

    M., Starkey, D

    Fausnaugh, M. M., Starkey, D. A., Horne, K., et al.\ 2018, , 854, 107. doi:10.3847/1538-4357/aaaa2b

    2018 doi

  20. [28]

    doi:10.1088/1674-4527/18/2/21

    Feng, H.-C., Liu, H.-T., Zhao, Y.-H., et al.\ 2018, Research in Astronomy and Astrophysics, 18, 021. doi:10.1088/1674-4527/18/2/21

    2018 doi

  21. [29]

    T., Bai, J

    Feng, H.-C., Liu, H. T., Bai, J. M., et al.\ 2020, , 888, 30. doi:10.3847/1538-4357/ab594b

    2020 doi

  22. [30]

    doi:10.3847/1538-4357/abd851

    Feng, H.-C., Hu, C., Li, S.-S., et al.\ 2021a, , 909, 18. doi:10.3847/1538-4357/abd851

    doi

  23. [31]

    T., Bai, J

    Feng, H.-C., Liu, H. T., Bai, J. M., et al.\ 2021b, , 912, 92. doi:10.3847/1538-4357/abefe0

    doi

  24. [32]

    M., et al.\ 2024, , 976, 176

    Feng, H.-C., Li, S.-S., Bai, J. M., et al.\ 2024, , 976, 176. doi:10.3847/1538-4357/ad8568

    2024 doi

  25. [33]

    doi:10.1051/0004-6361/202244905

    Fian, C., Chelouche, D., Kaspi, S., et al.\ 2023, , 672, A132. doi:10.1051/0004-6361/202244905

    2023 doi

  26. [34]

    L.\ 1999, , 111, 63

    Fitzpatrick, E. L.\ 1999, , 111, 63. doi:10.1086/316293

    1999 doi

  27. [35]

    doi:10.3847/1538-3881/abe9bc

    F \"o rster, F., Cabrera-Vives, G., Castillo-Navarrete, E., et al.\ 2021, , 161, 242. doi:10.3847/1538-3881/abe9bc

    2021 doi

  28. [36]

    \'E ., Smith, K., Frey, S., et al.\ 2023, arXiv:2304.10125

    Gab \'a nyi, K. \'E ., Smith, K., Frey, S., et al.\ 2023, arXiv:2304.10125. doi:10.48550/arXiv.2304.10125

    2023 doi arXiv

  29. [37]

    Gaskell, C. M. & Sparke, L. S.\ 1986, , 305, 175. doi:10.1086/164238

    1986 doi

  30. [38]

    Gaskell, C. M. & Peterson, B. M.\ 1987, , 65, 1. doi:10.1086/191216

    1987 doi

  31. [39]

    Gaskell, C. M. & Goosmann, R. W.\ 2013, , 769, 30. doi:10.1088/0004-637X/769/1/30

    2013 doi

  32. [40]

    Gaskell, C. M. & Goosmann, R. W.\ 2016, , 361, 67. doi:10.1007/s10509-015-2648-1

    2016 doi

  33. [41]

    R., Korista, K

    Goad, M. R., Korista, K. T., & Ruff, A. J.\ 2012, , 426, 3086. doi:10.1111/j.1365-2966.2012.21808.x

    2012

  34. [42]

    J., Kulkarni, S

    Graham, M. J., Kulkarni, S. R., Bellm, E. C., et al.\ 2019, , 131, 078001. doi:10.1088/1538-3873/ab006c

    2019 doi

  35. [43]

    doi:10.1038/s41586-018-0731-9

    Gravity Collaboration, Sturm, E., Dexter, J., et al.\ 2018, , 563, 657. doi:10.1038/s41586-018-0731-9

    2018 doi

  36. [44]

    doi:10.1051/0004-6361/202039067

    GRAVITY Collaboration, Amorim, A., Baub \"o ck, M., et al.\ 2020, , 643, A154. doi:10.1051/0004-6361/202039067

    2020 doi

  37. [45]

    J., Hey, D., et al.\ 2023, arXiv:2304.03791

    Hart, K., Shappee, B. J., Hey, D., et al.\ 2023, arXiv:2304.03791. doi:10.48550/arXiv.2304.03791

    2023 doi arXiv

  38. [46]

    M., et al.\ 2021, , 907, 76

    Horne, K., De Rosa, G., Peterson, B. M., et al.\ 2021, , 907, 76. doi:10.3847/1538-4357/abce60

    2021 doi

  39. [47]

    doi:10.1088/0004-637X/804/2/138

    Hu, C., Du, P., Lu, K.-X., et al.\ 2015, , 804, 138. doi:10.1088/0004-637X/804/2/138

    2015 doi

  40. [48]

    doi:10.3847/1538-4365/abd774

    Hu, C., Li, S.-S., Yang, S., et al.\ 2021, , 253, 20. doi:10.3847/1538-4365/abd774

    2021 doi

  41. [49]

    doi:10.3847/1538-4357/ab6a17

    Hu, C., Li, Y.-R., Du, P., et al.\ 2020, , 890, 71. doi:10.3847/1538-4357/ab6a17

    2020 doi

  42. [50]

    C., et al.\ 2021, , 501, 916

    Jiang, J., Cheng, H., Gallo, L. C., et al.\ 2021, , 501, 916. doi:10.1093/mnras/staa3737

    2021 doi

  43. [51]

    S., Netzer, H., et al.\ 2000, , 533, 631

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

    2000 doi

  44. [52]

    C.\ 2007, , 665, 1489

    Kelly, B. C.\ 2007, , 665, 1489. doi:10.1086/519947

    2007 doi

  45. [53]

    S., Shappee, B

    Kochanek, C. S., Shappee, B. J., Stanek, K. Z., et al.\ 2017, , 129, 104502. doi:10.1088/1538-3873/aa80d9

    2017 doi

  46. [54]

    Korista, K. T. & Goad, M. R.\ 2000, , 536, 284. doi:10.1086/308930

    2000 doi

  47. [55]

    Korista, K. T. & Goad, M. R.\ 2004, , 606, 749. doi:10.1086/383193

    2004 doi

  48. [56]

    doi:10.3847/1538-4357/ac116e

    Li, S.-S., Yang, S., Yang, Z.-X., et al.\ 2021, , 920, 9. doi:10.3847/1538-4357/ac116e

    2021 doi

  49. [57]

    T., et al.\ 2022, , 936, 75

    Li, S.-S., Feng, H.-C., Liu, H. T., et al.\ 2022, , 936, 75. doi:10.3847/1538-4357/ac8745

    2022 doi

  50. [58]

    T., et al.\ 2024a, arXiv:2407.05414

    Li, S.-S., Feng, H.-C., Liu, H. T., et al.\ 2024a, arXiv:2407.05414. doi:10.48550/arXiv.2407.05414

    doi arXiv

  51. [59]

    Li, Y.-R.\ 2024, PyCALI: A Bayesian package for intercalibrating light curves, v0.2.3, Zenodo, doi:10.5281/zenodo.10700132

    2024 doi

  52. [60]

    doi:10.1088/2041-8205/786/1/L6

    Li, Y.-R., Wang, J.-M., Hu, C., et al.\ 2014, , 786, L6. doi:10.1088/2041-8205/786/1/L6

    2014 doi

  53. [61]

    doi:10.3847/1538-4357/aaee6b

    Li, Y.-R., Songsheng, Y.-Y., Qiu, J., et al.\ 2018, , 869, 137. doi:10.3847/1538-4357/aaee6b

    2018 doi

  54. [62]

    T., Feng, H

    Liu, H. T., Feng, H. C., & Bai, J. M.\ 2017, , 466, 3323. doi:10.1093/mnras/stw3261

    2017 doi

  55. [63]

    T., Feng, H.-C., Li, S.-S., et al.\ 2024, , 963, 30

    Liu, H. T., Feng, H.-C., Li, S.-S., et al.\ 2024, , 963, 30. doi:10.3847/1538-4357/ad1ab8

    2024 doi

  56. [64]

    doi:10.3847/1538-4365/ac94d3

    Lu, K.-X., Bai, J.-M., Wang, J.-M., et al.\ 2022, , 263, 10. doi:10.3847/1538-4365/ac94d3

    2022 doi

  57. [65]

    doi:10.3847/1538-4357/ab5790

    Lu, K.-X., Bai, J.-M., Zhang, Z.-X., et al.\ 2019, , 887, 135. doi:10.3847/1538-4357/ab5790

    2019 doi

  58. [66]

    doi:10.3847/1538-4357/acc4c1

    Ma, Q., Wu, X.-B., Gu, H., et al.\ 2023, , 949, 22. doi:10.3847/1538-4357/acc4c1

    2023 doi

  59. [67]

    doi:10.1093/mnras/stad145

    Malik, U., Sharp, R., Penton, A., et al.\ 2023, , 520, 2009. doi:10.1093/mnras/stad145

    2023 doi

  60. [68]

    J., Maiolino, R., et al.\ 2008, , 678, 693

    Marconi, A., Axon, D. J., Maiolino, R., et al.\ 2008, , 678, 693. doi:10.1086/529360

    2008 doi

  61. [69]

    W., et al.\ 2018, Frontiers in Astronomy and Space Sciences, 5, 6

    Marziani, P., Dultzin, D., Sulentic, J. W., et al.\ 2018, Frontiers in Astronomy and Space Sciences, 5, 6. doi:10.3389/fspas.2018.00006

    2018

  62. [70]

    J., Laher, R

    Masci, F. J., Laher, R. R., Rusholme, B., et al.\ 2019, , 131, 018003. doi:10.1088/1538-3873/aae8ac

    2019 doi

  63. [71]

    A., et al.\ 1995, , 451, 498

    Murray, N., Chiang, J., Grossman, S. A., et al.\ 1995, , 451, 498. doi:10.1086/176238

    1995 doi

  64. [72]

    doi:10.3847/1538-4357/ac139d

    Naddaf, M.-H., Czerny, B., & Szczerba, R.\ 2021, , 920, 30. doi:10.3847/1538-4357/ac139d

    2021 doi

  65. [73]

    Netzer, H.\ 2013, The Physics and Evolution of Active Galactic Nuclei, by Hagai Netzer, Cambridge, UK: Cambridge University Press, 2013

    2013

  66. [74]

    doi:10.1146/annurev-astro-082214-122302

    Netzer, H.\ 2015, , 53, 365. doi:10.1146/annurev-astro-082214-122302

    2015 doi

  67. [75]

    & Marziani, P.\ 2010, , 724, 318

    Netzer, H. & Marziani, P.\ 2010, , 724, 318. doi:10.1088/0004-637X/724/1/318

    2010 doi

  68. [76]

    A., Ferrarese, L., Merritt, D., et al.\ 2004, , 615, 645

    Onken, C. A., Ferrarese, L., Merritt, D., et al.\ 2004, , 615, 645. doi:10.1086/424655

    2004 doi

  69. [77]

    E.\ 1978, Proceedings of the National Academy of Science, 75, 540

    Osterbrock, D. E.\ 1978, Proceedings of the National Academy of Science, 75, 540. doi:10.1073/pnas.75.2.540

    1978 doi

  70. [78]

    Osterbrock, D. E. & Mathews, W. G.\ 1986, , 24, 171. doi:10.1146/annurev.aa.24.090186.001131

    1986

  71. [79]

    doi:10.31577/caosp.2020.50.1.293

    Panda, S., Marziani, P., & Czerny, B.\ 2020, Contributions of the Astronomical Observatory Skalnate Pleso, 50, 293. doi:10.31577/caosp.2020.50.1.293

    2020 doi

  72. [80]

    doi:10.3389/fspas.2024.1479874

    Panda, S.\ 2024, Frontiers in Astronomy and Space Sciences, 11, 1479874. doi:10.3389/fspas.2024.1479874

    2024

  73. [81]

    J., & Treu, T.\ 2011, , 730, 139

    Pancoast, A., Brewer, B. J., & Treu, T.\ 2011, , 730, 139. doi:10.1088/0004-637X/730/2/139

    2011 doi

  74. [82]

    J., Treu, T., et al.\ 2012, , 754, 49

    Pancoast, A., Brewer, B. J., Treu, T., et al.\ 2012, , 754, 49. doi:10.1088/0004-637X/754/1/49

    2012 doi

  75. [83]

    J., Horne, K., et al.\ 2018, , 856, 108

    Pancoast, A., Barth, A. J., Horne, K., et al.\ 2018, , 856, 108. doi:10.3847/1538-4357/aab3c6

    2018 doi

  76. [84]

    M.\ 1997, An introduction to active galactic nuclei, Publisher: Cambridge, New York Cambridge University Press, 1997 Physical description xvi, 238 p

    Peterson, B. M.\ 1997, An introduction to active galactic nuclei, Publisher: Cambridge, New York Cambridge University Press, 1997 Physical description xvi, 238 p. ISBN 0521473489

    1997

  77. [85]

    M., Ferrarese, L., Gilbert, K

    Peterson, B. M., Ferrarese, L., Gilbert, K. M., et al.\ 2004, , 613, 682. doi:10.1086/423269

    2004 doi

  78. [86]

    Peterson, B. M. & Wandel, A.\ 1999, , 521, L95. doi:10.1086/312190

    1999 doi

  79. [87]

    M., Wanders, I., Horne, K., et al.\ 1998, , 110, 660

    Peterson, B. M., Wanders, I., Horne, K., et al.\ 1998, , 110, 660. doi:10.1086/316177

    1998 doi

  80. [88]

    M.\ 1993, , 105, 247

    Peterson, B. M.\ 1993, , 105, 247. doi:10.1086/133140

    1993 doi

  81. [89]

    doi:10.1051/0004-6361/201833910

    Planck Collaboration, Aghanim, N., Akrami, Y., et al.\ 2020, , 641, A6. doi:10.1051/0004-6361/201833910

    2020 doi

  82. [90]

    & Kallman, T

    Proga, D. & Kallman, T. R.\ 2004, , 616, 688. doi:10.1086/425117

    2004 doi

  83. [91]

    & Trakhtenbrot, B.\ 2023, Nature Astronomy, 7, 1282

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

    2023 doi

  84. [92]

    M., Alloin, D., Clavel, J., et al.\ 1997, , 110, 9

    Rodr \' guez-Pascual, P. M., Alloin, D., Clavel, J., et al.\ 1997, , 110, 9. doi:10.1086/312996

    1997 doi

  85. [93]

    A., Robinson, A., Almeyda, T., et al.\ 2024, , 965, 35

    Rosborough, S. A., Robinson, A., Almeyda, T., et al.\ 2024, , 965, 35. doi:10.3847/1538-4357/ad26f3

    2024 doi

  86. [94]

    N., Cosens, M., Bennert, V

    Runco, J. N., Cosens, M., Bennert, V. N., et al.\ 2016, , 821, 33. doi:10.3847/0004-637X/821/1/33

    2016 doi

  87. [95]

    doi:10.3847/1538-3881/abd5c1

    S \'a nchez-S \'a ez, P., Reyes, I., Valenzuela, C., et al.\ 2021, , 161, 141. doi:10.3847/1538-3881/abd5c1

    2021 doi

  88. [96]

    Schlafly, E. F. & Finkbeiner, D. P.\ 2011, , 737, 103. doi:10.1088/0004-637X/737/2/103

    2011 doi

  89. [97]

    2012, PyRAF: Python alternative for IRAF , Astrophysics Source Code Library, record ascl:1207.011

    Science Software Branch at STScI . 2012, PyRAF: Python alternative for IRAF , Astrophysics Source Code Library, record ascl:1207.011

    2012

  90. [98]

    J., Prieto, J

    Shappee, B. J., Prieto, J. L., Grupe, D., et al.\ 2014, , 788, 48. doi:10.1088/0004-637X/788/1/48

    2014 doi

  91. [99]

    S., Peterson, B

    Storchi-Bergmann, T., Schimoia, J. S., Peterson, B. M., et al.\ 2017, , 835, 236. doi:10.3847/1538-4357/835/2/236

    2017 doi

  92. [100]

    J., Vogler, H

    U, V., Barth, A. J., Vogler, H. A., et al.\ 2022, , 925, 52. doi:10.3847/1538-4357/ac3d26

    2022 doi

  93. [101]

    R., Treu, T., et al.\ 2022, , 930, 52

    Villafa \ n a, L., Williams, P. R., Treu, T., et al.\ 2022, , 930, 52. doi:10.3847/1538-4357/ac6171

    2022 doi

  94. [102]

    S., et al.\ 2017, Nature Astronomy, 1, 775

    Wang, J.-M., Du, P., Brotherton, M. S., et al.\ 2017, Nature Astronomy, 1, 775. doi:10.1038/s41550-017-0264-4

    2017 doi

  95. [103]

    doi:10.3847/1538-4357/abb36d

    Wang, S., Shen, Y., Jiang, L., et al.\ 2020, , 903, 51. doi:10.3847/1538-4357/abb36d

    2020 doi

  96. [104]

    Welsh, W. F. & Horne, K.\ 1991, , 379, 586. doi:10.1086/170530

    1991 doi

  97. [105]

    doi:10.1086/191644

    Whittle, M.\ 1992, , 79, 49. doi:10.1086/191644

    1992 doi

  98. [106]

    White, R. J. & Peterson, B. M.\ 1994, , 106, 879. doi:10.1086/133456

    1994 doi

  99. [107]

    R., Treu, T., Dahle, H., et al.\ 2021, , 915, L9

    Williams, P. R., Treu, T., Dahle, H., et al.\ 2021, , 915, L9. doi:10.3847/2041-8213/ac081b

    2021 doi

  100. [108]

    doi:10.3847/1538-4357/ad132f

    Woo, J.-H., Wang, S., Rakshit, S., et al.\ 2024, , 962, 67. doi:10.3847/1538-4357/ad132f

    2024 doi

  101. [109]

    doi:10.1088/0004-637X/801/1/38

    Woo, J.-H., Yoon, Y., Park, S., et al.\ 2015, , 801, 38. doi:10.1088/0004-637X/801/1/38

    2015 doi

  102. [110]

    doi:10.3847/1538-4357/ab3ebc

    Yan, R., Chen, Y., Lazarz, D., et al.\ 2019, , 883, 175. doi:10.3847/1538-4357/ab3ebc

    2019 doi

  103. [111]

    doi:10.3847/1538-4357/ad72ef

    Yao, Z.-H., Yang, S., Guo, W.-J., et al.\ 2024, , 975, 41. doi:10.3847/1538-4357/ad72ef

    2024 doi

  104. [112]

    doi:10.48550/arXiv.2408.11292

    Zhou, S., Sun, M., Feng, H.-C., et al.\ 2024, arXiv:2408.11292. doi:10.48550/arXiv.2408.11292

    2024 doi arXiv

Pith tools

Reviewed August 11, 2026 · model on record in the stance chip above.