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Gemini Near Infrared Spectrograph$-$Distant Quasar Survey: the Chandra View

T0 review · 3 major / 5 minor · reviewed 2026-08-06 · deepseek-v4-flash

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Pith's one-line read Chandra observations of 63 distant quasars show that the optical-to-X-ray slope does not improve Hβ- or C IV-based accretion-rate estimates, and that C IV remains the better Eddington-ratio indicator up to z~3.5.

desk verdict Useful new X-ray data for 63 GNIRS-DQS quasars, but the abstract's 'does not improve' claim about alpha_ox outruns the reported statistics. read the letter →

arxiv 2507.22272 v1 pith:K5QVBGTB submitted 2025-07-29 astro-ph.GA

Andrea Marlar (1) , Ohad Shemmer (1) , Michael S. Brotherton (2) , Gordon T. Richards (3) , Cooper Dix (4) , Brandon M. Matthews (1) , W. N. Brandt (5) , R. M. Plotkin (6
show 7 more authors
7) ((1) U. North Texas (2) U. Wyoming (3) Drexel U. (4) U. Texas at Austin (5) Penn State U. (6) U. Nevada at Reno (7) U. Nevada at Las Vegas)
This is my paper
classification astro-ph.GA
keywords quasarsaccretionrateEddingtonratioX-rayobservationsCIVemissionlinesoptical-to-X-rayspectralslopeChandraGNIRS-DQS
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 sets out to test whether basic X-ray measurements can serve as a practical accretion-rate indicator for distant quasars, where the usual optical emission lines are hard to obtain. With Chandra observations of 63 quasars from the Gemini Near Infrared Spectrograph-Distant Quasar Survey at $1.5\lesssim z \lesssim 3.5$, 55 of them clearly detected in X-rays, it finds that the optical-to-X-ray slope $\alpha_{\mathrm{ox}}$ does not significantly correlate with, and does not improve, $\mathrm{H}\beta$-based Eddington ratio estimates. The C IV emission-line parameter space, specifically the C IV $\parallel$ Distance combination of equivalent width and blueshift, does correlate with $L/L_{\mathrm{Edd}}$ and remains the preferred indicator up to $z\sim3.5$. The result matters because planned wide-area surveys will find quasars at the highest redshifts whose $\mathrm{H}\beta$ is inaccessible; the paper's answer is that X-ray brightness alone will not fill that gap.

What carries the argument

The load-bearing quantity is the $\mathrm{C\,IV}\parallel$Distance parameter, defined as the distance along a best-fit curve through the C IV equivalent-width versus blueshift plane, which encodes how far a source sits from typical C IV line behavior. It is the optical-UV variable that carries the accretion-rate signal in this paper: it correlates strongly with the Fe II-corrected $\mathrm{H}\beta$-based $L/L_{\mathrm{Edd}}$, while $\alpha_{\mathrm{ox}}$ does not. The reference accretion-rate scale is set by the Fe II-corrected $\mathrm{H}\beta$ estimator, and the X-ray side is carried by Chandra ACIS snapshots that yield $\alpha_{\mathrm{ox}}$ from 2 keV and 2500 Å flux densities and, for a small subset, effective or fitted photon indices $\Gamma$.

What would settle it

A decisive test would be a sample of roughly one hundred quasars spanning a wider range of 2500 Å luminosity and Eddington ratio than this one, with Chandra exposures deep enough to measure each source's photon index to $\pm0.2$; if $\alpha_{\mathrm{ox}}$ still shows no correlation with Fe II-corrected $\mathrm{H}\beta$-based $L/L_{\mathrm{Edd}}$ after removing the luminosity dependence, the paper's negative conclusion is general, whereas if such a correlation appears, the negative result is a selection artifact.

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Extended reading notes

Core claim

The paper's claim, stated as a fair reader would hear it, is that the relative X-ray brightness of a quasar, quantified by $\alpha_{\mathrm{ox}}$, is not a competitive Eddington-luminosity-ratio diagnostic at $z\sim1.5$–$3.5$ and adds nothing to optical-UV estimates. For the 55 X-ray-detected GNIRS-DQS sources, $\alpha_{\mathrm{ox}}$ shows no significant correlation with Fe II-corrected $\mathrm{H}\beta$-based $L/L_{\mathrm{Edd}}$ ($r_S=-0.245$, $p=0.071$), whereas the $\mathrm{C\,IV}\parallel$Distance parameter correlates significantly with $L/L_{\mathrm{Edd}}$ ($r_S=0.503$, $p<0.001$). The paper therefore confirms earlier work identifying the C IV parameter space as a better accretion-rate indicator up to at least $z\sim3.5$. Average hard-X-ray photon indices from joint spectral fits are $\gtrsim1.8$, consistent with the sample's relatively high Eddington ratios, but individual $\Gamma$ values from the short snapshot exposures are too uncertain to serve as a diagnostic without deeper observations.

Load-bearing premise

The result rests on the 54 brightest GNIRS-DQS quasars that had no prior sensitive X-ray coverage, with broad-absorption-line and radio-loud sources removed; if this selection compressed the range of X-ray weakness and Eddington ratios, the missing correlation between $\alpha_{\mathrm{ox}}$ and accretion rate could be an artifact of the chosen parameter space.

Editorial extensions

If this is right

  • A quasar's X-ray brightness, by itself, should not be used as a proxy for its Eddington ratio in luminous sources at $z\sim1.5$–$3.5$; the correlation is too weak and is likely mixed with black-hole-mass dependence.
  • The C IV $\parallel$ Distance parameter remains the most reliable optical-UV accretion-rate indicator tested here, which is valuable for high-redshift quasars where $\mathrm{H}\beta$ is redshifted out of reach.
  • Adding $\alpha_{\mathrm{ox}}$ information does not reduce the scatter in existing $L/L_{\mathrm{Edd}}$ estimates based on $\mathrm{H}\beta$ or C IV.
  • The average hard-X-ray photon index of the sample is consistent with high Eddington ratios, but demonstrating that $\Gamma$ can serve as an unbiased diagnostic requires deeper X-ray exposures than the snapshot observations used in this paper.

Reading between the lines

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

  • A natural extension, not tested in the paper, is that the non-correlation of $\alpha_{\mathrm{ox}}$ with $L/L_{\mathrm{Edd}}$ may be confined to the bright, narrow-luminosity window of this sample; a sample spanning fainter quasars and a wider Eddington-ratio range could reveal a residual correlation after controlling for black-hole mass.
  • If deep X-ray follow-up shows that individual $\Gamma$ values correlate with $L/L_{\mathrm{Edd}}$ more tightly than $\alpha_{\mathrm{ox}}$ does, the paper's negative result would motivate a two-tier strategy: C IV line measurements for survey-scale samples, and deep X-ray spectra only for the most important objects.
  • The paper's own caveat that a considerably larger sample is needed to separate the $\alpha_{\mathrm{ox}}$ dependence on $L/L_{\mathrm{Edd}}$ and black-hole mass means its main negative conclusion is most secure for the high-luminosity end and should be re-tested where those two variables decouple.
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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

3 major / 5 minor

Summary. The paper presents new Chandra ACIS observations of 63 quasars from the GNIRS-DQS sample, 54 of them obtained as Cycle 24 snapshot observations and 9 taken from archival M22 data. Of these, 55 sources are detected in at least one X-ray band and 8 receive upper limits. The authors derive alpha_ox assuming a fixed photon index Gamma=2.0 with systematic errors from Gamma=1.6 and 2.4, and combine these values with FeII-corrected Hbeta-based L/L_Edd and CIV\parallel Distance from earlier work by the same group. They report correlations among alpha_ox, L_2500, L/L_Edd, and CIV\parallel Distance, finding that alpha_ox is not a competitive L/L_Edd indicator and that the CIV parameter space remains preferable up to z~3.5. They also derive effective Gamma values for a small subset and jointly fit stacked spectra in redshift, luminosity, and L/L_Edd bins, finding average Gamma values generally consistent with relatively high Eddington ratios.

Significance. The new X-ray data are a valuable resource: the sample is uniform, the reduction follows standard CIAO and XSPEC procedures, and the treatment of low-count Poisson errors and upper limits is careful and documented. If the central claim is accepted, the paper would quantitatively support the view that simple X-ray brightness information does not rival CIV-based accretion-rate diagnostics at z~1.5-3.5, which is directly relevant for planning studies of the highest-redshift quasars. The paper is also honest about its limitations, repeatedly noting the small number of usable Gamma measurements and the need for deeper observations. However, the main negative claim is currently supported only by marginal correlations and visual inspection, so the significance of the result depends on an additional incremental-predictive-power test that is not yet present.

major comments (3)
  1. [Section 3.1.4 and Abstract] The abstract's central claim that alpha_ox "does not improve current accretion-rate estimates" is not directly tested by the reported statistics. Section 3.1.4 compares the marginal Spearman correlation of alpha_ox with L/L_Edd (r_S=-0.245, p=0.071) to that of CIV\parallel Distance with L/L_Edd (r_S=0.503, p<<0.001). A predictor with a negligible marginal correlation can still add incremental predictive power after another correlated predictor is accounted for, and the phrase "does not improve" specifically requires a partial correlation, multiple regression, or residual-based test. The p=0.071 value also leaves a wide confidence interval that does not exclude a moderate negative correlation. Please add such an incremental test, or soften the abstract and summary claims accordingly.
  2. [Section 2 and Section 3.1.2] The principal negative result rests on a non-random sample: the 54 brightest GNIRS-DQS sources without prior sensitive X-ray coverage, excluding BAL and radio-loud quasars. Section 3.1.2 reports r_S=-0.245, p=0.071 for alpha_ox versus L/L_Edd over the 55 X-ray-detected sources, but the sample spans only about one order of magnitude in log L_2500 (Table 2) and a restricted range of L/L_Edd. The absence of a correlation could therefore be an artifact of the selected parameter space rather than a general property. The authors acknowledge the narrow luminosity range, but they do not quantify the ranges of L/L_Edd and alpha_ox or test whether the selection truncates the relevant parameter space; adding this quantitative context would substantially strengthen the interpretation.
  3. [Section 3.2 and Table 6] The second abstract claim, that the average Gamma values are consistent with the relatively high L/L_Edd values, is not quantitatively connected to the published Gamma-L/L_Edd relation. Table 4 reports joint-fit Gamma values near 1.8 with typical uncertainties of about 0.15-0.3, and Table 6 shows no trend in Gamma across L/L_Edd bins, but the paper does not state the Gamma value expected from Shemmer et al. (2008) or a similar relation at the relevant L/L_Edd. Adding that expected value and a formal consistency check would make the claim testable rather than qualitative.
minor comments (5)
  1. [Table 3] The source name in Table 3, SDSS J144948.62+123047.5, differs from the corresponding entry in Table 2, SDSS J144948.62+123047.4; please correct the inconsistency.
  2. [Section 1] The text contains a typo, "dependance", which should be "dependence".
  3. [Section 3.1.2] The sentence "We find no significant Spearman-rank correlations..." refers to the 55-source GNIRS-DQS sample, but when the 22 M22 sources are added the alpha_ox-L/L_Edd correlation becomes r_S=-0.275 with p=0.016, which is nominally significant; please clarify that the statement applies to the GNIRS-DQS-only sample and discuss the change.
  4. [Section 3.1.4 and Figure 5] The quantitative comparison of mean alpha_ox above and below the median L/L_Edd (a difference of 0.05) and above and below the median CIV\parallel Distance (a difference of 0.11) is reported without uncertainties or a statistical test; please provide errors on these means and a formal test, or describe the comparison as qualitative.
  5. [Section 2] The text says "Only seven of our sources were not detected" while the abstract and Table 2 imply eight undetected sources in the full 63-source sample; please clarify that seven refers to the targeted sample and one additional non-detection comes from the archival sample.

Circularity Check

0 steps flagged · score 1.0 of 10

No significant circularity: the X-ray α_ox measurements are independent of the Hβ-based L/L_Edd and CIV∥Distance diagnostics, and the key correlations are empirically recomputed on the new sample.

full rationale

The paper's load-bearing claim is an empirical negative result: α_ox shows no significant Spearman correlation with Hβ-based L/L_Edd, while CIV∥Distance does. The α_ox values are new measurements derived independently from Chandra flux densities and SDSS 2500 Å flux densities; no equation defining α_ox contains L/L_Edd, and no L/L_Edd value is fitted from α_ox. The Hβ-based L/L_Edd and CIV∥Distance columns are imported from H23, R22, and Maithil et al., which share authors with this paper, but the paper recomputes the key correlations on its own 63-source sample and compares them with the X-ray correlations. The statement that α_ox 'does not improve' current estimates is weaker than the evidence presented, because only zero-order correlations are reported rather than an incremental predictive test, but this is an inference gap, not a circular derivation. The CIV∥Distance parameter is defined as a distance along an EW-blue-shift curve, not in terms of L/L_Edd, so the CIV∥Distance–L/L_Edd correlation is not true by construction. Self-citation is heavy but not load-bearing: the new X-ray data are independent of the optical-UV diagnostics, and the central negative conclusion rests on the reported correlation values rather than on an unverified self-citation chain. A small score is appropriate only to reflect the inherited H23/R22/Maithil calibrations and the absence of an independent, out-of-sample test of the CIV-based estimator.

Assumptions & free parameters 1 free parameters · 5 assumptions · 0 invented entities

No new physical entities are introduced, and the paper contributes no new fitted constants. The only number chosen by hand in this work is the fixed photon index Gamma=2.0 used for flux conversion, bracketed by 1.6 and 2.4. The empirical calibrations for FeII-corrected L/L_Edd, C IV parallel Distance, and Delta alpha_ox are imported from prior papers and are listed as domain assumptions limiting the analysis.

free parameters (1)
  • Fixed photon index Gamma for 2 keV flux conversion = 2.0
    Chosen in Section 2 to convert X-ray counts to f_2 keV; every alpha_ox value inherits this modeling choice, with errors bracketed by Gamma=1.6 and 2.4.
assumptions (5)
  • domain assumption Single-epoch H beta and 5100 A luminosities provide virial black-hole masses and FeII-corrected Eddington ratios.
    All L/L_Edd values come from Matthews et al. (2023) and H23, assuming a virialized broad-line region and calibrated virial factors.
  • domain assumption Hard X-ray spectra are power laws from a hot corona, with photon index tracking Eddington ratio.
    Section 1 introduces the Gamma-L/L_Edd relation, and Section 3.2 interprets measured and stacked Gamma values as consistent with high Eddington ratios.
  • domain assumption C IV parallel Distance, a combination of EW and blueshift, is a valid empirical accretion-rate indicator.
    The paper trusts the R22 and H23 calibration of C IV parallel Distance against L/L_Edd when comparing it with X-ray parameters.
  • domain assumption Rest-frame 2 keV flux densities are derived assuming a power law with Gamma=2.0 and no intrinsic absorption.
    Section 2 states f_2 keV is obtained with PHABS*POW and Gamma fixed to 2.0; errors are bracketed by Gamma=1.6 and 2.4.
  • domain assumption The Timlin et al. (2020) alpha_ox-L2500 relation fully accounts for luminosity dependence in Delta alpha_ox.
    Delta alpha_ox in Section 3.1.1 is defined against Equation 3 of Timlin et al. (2020); residual correlations with L2500 are interpreted as sample effects.

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Pith. "Pith review of Gemini Near Infrared Spectrograph$-$Distant Quasar Survey: the Chandra View." pith.science (2026). https://pith.science/paper/K5QVBGTB

@misc{pith2026250722272,
  author       = {Pith},
  title        = {Pith review of: Gemini Near Infrared Spectrograph$-$Distant Quasar Survey: the Chandra View},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/K5QVBGTB}},
  note         = {Machine review of arXiv:2507.22272}
}
abstract

We present Chandra observations of 63 sources from the Gemini Near Infrared Spectrograph$-$Distant Quasar Survey (GNIRS-DQS) of which 54 were targeted by snapshot observations in Cycle 24. A total of 55 sources are clearly detected in at least one X-ray band, and we set stringent upper limits on the X-ray fluxes of the remaining eight sources. In combination with rest-frame ultraviolet-optical spectroscopic data for these sources, we assess whether X-rays can provide a robust accretion-rate indicator for quasars, particularly at the highest accessible redshifts. We utilize a recently modified H$\beta$-based Eddington luminosity ratio estimator, as well as the C IV $\lambda$1549 emission-line parameter space to investigate trends and correlations with the optical-X-ray spectral slope ($\alpha_{\mathrm{ox}}$) and the effective hard-X-ray power-law photon index ($\Gamma$). We find that $\alpha_{\mathrm{ox}}$ does not improve current accretion-rate estimates based on H$\beta$ or C IV. Instead, within the limitations of our sample, we confirm previous findings that the C IV parameter space may be a better indicator of the accretion rate up to $z\sim3.5$. We also find that the average $\Gamma$ values for a small subset of our sources, as well as the average $\Gamma$ value in different groupings of our sources, are consistent with their respective relatively high Eddington luminosity ratios. Deeper X-ray observations of our X-ray-detected sources are needed for measuring $\Gamma$ accurately and testing whether this parameter can serve as a robust, un-biased accretion-rate diagnostic.

Figures

Figures reproduced from arXiv: 2507.22272 by the authors.

Figure 1
Figure 1. Optical-to-X-ray spectral slope (αox) (top) and the lumi￾nosity corrected αox value, ∆αox (bottom) versus L2500A˚ . Red dia￾monds represent X-ray-detected sources from this work, with blue arrows representing X-ray-undetected sources; green and black cir￾cles represent sources from M22 and R22, respectively; median er￾ror bars are shown in the lower left-hand corner of each panel, for clarity. The solid line in the … view at source ↗
Figure 3
Figure 3. Same as [PITH_FULL_IMAGE:figures/full_fig_p011_3.png] view at source ↗
Figure 4
Figure 4. The C IV ∥ Distance parameter versus Hβ-based L/LEdd. Black (green) circles represent 248 (21) sources from H23 (M22). Red diamonds (blue arrows) represent X-ray-detected (X-ray-undetected) sources from this work, which constitute a subsample of H23 sources, and the solid line represents the best fit relation from H23. C IV ∥ D i s t a n c e 1 0.2 Hβ-based L/LEdd 0.01 0.1 1 10 [PITH_FULL_IMAGE:figures/full_fig_p012… view at source ↗
Figures from the paper (6 more)
Figure 5
Figure 5. Figure 5: Same as [PITH_FULL_IMAGE:figures/full_fig_p012_5.png]
Figure 6
Figure 6. Figure 6: Data, best-fit spectra, and residuals of the four GNIRS-DQS sources with > 100 full-band counts. The data were fitted using a Galactic absorption power-law model with an added intrinsic neutral absorption component above a rest-frame energy of 2 keV. The χ residuals ar…
Figure 7
Figure 7. Figure 7: Contours representing confidence regions of 68%, 90%, and 99% for Γ versus NH for four sub-samples of GNIRS-DQS sources, as given in [PITH_FULL_IMAGE:figures/full_fig_p015_7.png]
Figure 8
Figure 8. Figure 8: Same as [PITH_FULL_IMAGE:figures/full_fig_p016_8.png]
Figure 9
Figure 9. Figure 9: Same as [PITH_FULL_IMAGE:figures/full_fig_p017_9.png]
Figure 10
Figure 10. Figure 10: Left: Venn-diagram of the overlap in sources between this work, M22, and R22. Right: The breakdown of all 53 M22 sources in regards to which sources have C IV data, Fe II data, both, or neither (see also [PITH_FULL_IMAGE:figures/full_fig_p018_10.png]

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Works this paper leans on

19 extracted references · 1 linked inside Pith

  1. [11]

    & Laor, A

    doi:10.3847/0067-0049/227/1/11 Baskin, A. & Laor, A. 2004, MNRAS, 350, L31. doi:10.1111/j.1365-2966.2004.07833.x Brightman, M., Silverman, J. D., Mainieri, V ., et al. 2013, MNRAS, 433, 2485. doi:10.1093/mnras/stt920 Cash, W. 1979, ApJ, 228, 939. doi:10.1086/156922 Coatman, L., Hewett, P. C., Banerji, M., et al. 2016, MNRAS, 461,

    arXiv 2004

  2. [20]

    N., Luo, B., et al

    doi:10.1088/0004-637X/726/1/20 Ni, Q., Brandt, W. N., Luo, B., et al. 2018, MNRAS, 480, 5184. doi:10.1093/mnras/sty1989 Onoue, M., Kashikawa, N., Matsuoka, Y ., et al. 2019, ApJ, 880,

    doi:10.1088/0004-637x/726/1/20 2018

  3. [41]

    L., del Olmo, A., Marziani, P., et al

    doi:10.3847/1538-4357/ac5f58 Mart´ınez-Aldama, M. L., del Olmo, A., Marziani, P., et al. 2018, A&A, 618, A179. doi:10.1051/0004-6361/201833541 Matthews, B. M., Dix, C., Shemmer, O., et al. 2023, ApJ, 950, 95. doi:10.3847/1538-4357/acd04c Matthews, B. M., Shemmer, O., Dix, C., et al. 2021, ApJS, 252, 15. doi:10.3847/1538-4365/abc705 Mej´ıa-Restrepo, J. E.,...

    arXiv doi:10.48550/arxiv.1209.3114 2018

  4. [77]

    L., Reeves, J

    doi:10.3847/1538-4357/ab29e9 Page, K. L., Reeves, J. N., O’Brien, P. T., et al. 2005, MNRAS, 364, 195. doi:10.1111/j.1365-2966.2005.09550.x Park, T., Kashyap, V . L., Siemiginowska, A., et al. 2006, ApJ, 652,

    arXiv 2005

  5. [96]

    B., Richards, G

    doi:10.3847/1538-4357/aba62c Rivera, A. B., Richards, G. T., Gallagher, S. C., et al. 2022, ApJ, 931, 154. doi:10.3847/1538-4357/ac6a5d Shemmer, O., Brandt, W. N., Netzer, H., et al. 2006, ApJL, 646, L29. doi:10.1086/506911 Shemmer, O., Brandt, W. N., Netzer, H., et al. 2008, ApJ, 682, 81. doi:10.1086/588776 Shemmer, O. & Lieber, S. 2015, ApJ, 805, 124. d...

    doi:10.3847/1538-4357/aba62c 2022

  6. [185]

    C., Brandt, W

    doi:10.1086/324017 Gallagher, S. C., Brandt, W. N., Chartas, G., et al. 2006, ApJ, 644,

    doi:10.1086/324017 2006

  7. [433]

    2021, ApJL, 907, L1

    doi:10.1086/345973 Wang, F., Yang, J., Fan, X., et al. 2021, ApJL, 907, L1. doi:10.3847/2041-8213/abd8c6 Weisskopf, M. C., Tananbaum, H. D., Van Speybroeck, L. P., et al. 2000, Proc. SPIE, 4012, 2. doi:10.1117/12.391545 Wu, J., Brandt, W. N., Anderson, S. F., et al. 2012, ApJ, 747, 10. doi:10.1088/0004-637X/747/1/10 Wu, J., Vanden Berk, D., Grupe, D., et ...

    doi:10.1086/345973 2021

  8. [610]

    N., et al

    doi:10.1086/507406 Pu, X., Luo, B., Brandt, W. N., et al. 2020, ApJ, 900, 141. doi:10.3847/1538-4357/abacc5 Rankine, A. L., Hewett, P. C., Banerji, M., et al. 2020, MNRAS, 492, 4553. doi:10.1093/mnras/staa130 22 MARLAR ET AL. Reed, S. L., Banerji, M., Becker, G. D., et al. 2019, MNRAS, 487,

    doi:10.1086/507406 2020

Show all 19 references
  1. [647]

    2009, ApJ, 705, 1336

    doi:10.1093/mnras/stw1360 Constantin, A., Green, P., Aldcroft, T., et al. 2009, ApJ, 705, 1336. doi:10.1088/0004-637X/705/2/1336 Dalla Bont`a, E., Peterson, B. M., Bentz, M. C., et al. 2020, ApJ, 903, 112. doi:10.3847/1538-4357/abbc1c Dickey, J. M. & Lockman, F. J. 1990, ARA&A...

    2009

  2. [709]

    P., Bautz, M

    doi:10.1086/503762 Garmire, G. P., Bautz, M. W., Ford, P. G., et al. 2003, Proc. SPIE, 4851, 28. doi:10.1117/12.461599 Gehrels, N. 1986, ApJ, 303, 336. doi:10.1086/164079 Gibson, R. R., Brandt, W. N., & Schneider, D. P. 2008, ApJ, 685,

    2003 doi

  3. [719]

    doi:10.1093/mnras/stz3433 Vasudevan, R. V . & Fabian, A. C. 2007, MNRAS, 381, 1235. doi:10.1111/j.1365-2966.2007.12328.x Vestergaard, M. & Peterson, B. M. 2006, ApJ, 641, 689. doi:10.1086/500572 Vignali, C., Brandt, W. N., & Schneider, D. P. 2003, AJ, 125, 2,

    2007

  4. [773]

    & Proga, D

    doi:10.1086/590403 Giustini, M. & Proga, D. 2019, A&A, 630, A94. doi:10.1051/0004-6361/201833810 Grier, C. J., Trump, J. R., Shen, Y ., et al. 2017, ApJ, 851, 21. doi:10.3847/1538-4357/aa98dc Grupe, D., Komossa, S., Leighly, K. M., et al. 2010, ApJS, 187, 64. doi:10.1088/0067-...

    2019

  5. [1004]

    I., Sramek, R., Schmidt, M., et al

    doi:10.1086/519990 Kellermann, K. I., Sramek, R., Schmidt, M., et al. 1989, AJ, 98,

    1989 doi

  6. [1163]

    N., Bean, R., Dor´e, O., et al

    doi:10.1086/498708 Spergel, D. N., Bean, R., Dor´e, O., et al. 2007, ApJS, 170, 377. doi:10.1086/513700 Steffen, A. T., Strateva, I., Brandt, W. N., et al. 2006, AJ, 131,

    2007 doi

  7. [1195]

    P., Burrows, D

    doi:10.1086/115207 Kraft, R. P., Burrows, D. N., & Nousek, J. A. 1991, ApJ, 374, 344. doi:10.1086/170124 Kubota, A. & Done, C. 2018, MNRAS, 480, 1247. doi:10.1093/mnras/sty1890 Laor, A. 1998, ApJL, 505, L83. doi:10.1086/311619 Liu, H., Luo, B., Brandt, W. N., et al. 2021, ApJ,...

    1991 doi

  8. [1579]

    F., Brandt, W

    doi:10.1086/301513 Zhu, S. F., Brandt, W. N., Luo, B., et al. 2020, MNRAS, 496, 245. doi:10.1093/mnras/staa1411 Zhu, S. F., Timlin, J. D., & Brandt, W. N. 2021, MNRAS, 505,

    2020 doi

  9. [1874]

    T., Kruczek, N

    doi:10.1093/mnras/stz1341 Richards, G. T., Kruczek, N. E., Gallagher, S. C., et al. 2011, AJ, 141, 167. doi:10.1088/0004-6256/141/5/167 Risaliti, G., Young, M., & Elvis, M. 2009, ApJL, 700, L6. doi:10.1088/0004-637X/700/1/L6 Rivera, A. B., Richards, G. T., Hewett, P. C., et al...

    2011 doi

  10. [1954]

    doi:10.1093/mnras/stab1406

    doi

  11. [2826]

    L., Fan, X., Wang, F., et al

    doi:10.1086/503627 Tee, W. L., Fan, X., Wang, F., et al. 2023, ApJ, 956, 52. doi:10.3847/1538-4357/acf12d Temple, M. J., Matthews, J. H., Hewett, P. C., et al. 2023, MNRAS, 523, 646. doi:10.1093/mnras/stad1448 Thomas, S. J., Barr, J., Callahan, S., et al. 2020, Proc. SPIE, 114...

    2023 doi

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