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REVIEW 4 major objections 9 minor 42 references

Searching for Internal Absorption Signatures in High-Redshift Blazars

T0 review · 4 major / 9 minor · reviewed 2026-08-08 · deepseek-v4-flash

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Pith's one-line read Distant blazar's gamma-ray source sits in its broad-line region.

desk verdict Careful, honest Fermi-LAT search for BLR absorption in high-z FSRQs with one modest hint, but the EBL double-counting from using 4FGL parameters as 'intrinsic' needs fixing before trusting the Source 3 constraint. read the letter →

arxiv 2502.04154 v1 pith:546SEHGB submitted 2025-02-06 astro-ph.HE

Anton Dmytriiev , Atreya Acharyya , Markus Böttcher This is my paper · ORCID
classification astro-ph.HE
keywords blazarsflat-spectrumradioquasarsgamma-rayabsorptionphoton-photonpairproductionbroad-lineregionFermi-LAThigh-redshiftAGNjetemission
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

High-redshift blazars offer a way to see internal gamma-ray absorption that would be invisible in nearby ones: at $z\gtrsim 3$, the absorption feature from broad-line-region Ly$\alpha$ photons shifts from $\sim 25$ GeV down to a few GeV, where Fermi-LAT collects many more photons. The paper analyzes nine $z\gtrsim 3$ flat-spectrum radio quasars and models each with a detailed $\gamma\gamma$ opacity calculation, scanning the distance $d$ of the gamma-ray production site from the supermassive black hole. Only one source, 4FGL J0733.8+0455 at $z=3.01$, shows a statistically meaningful response: the scan excludes $d<0.93\,R_{\mathrm{BLR}}$ at about $4\sigma$ and shows a $\sim 1.7\sigma$ preference for $d/R_{\mathrm{BLR}} = 0.95^{+0.09}_{-0.02}$, placing the emission region near the inner edge of the broad-line region. For the other eight sources, photon statistics are too poor to detect or exclude absorption, so no distance constraint can be placed. If the hint holds, it would be a direct indication that GeV emission in an FSRQ can be produced inside the BLR rather than far outside it.

What carries the argument

The machinery is a full-angle $\gamma\gamma$ opacity calculation that computes the optical depth $\tau_{\gamma\gamma}(E_\gamma,d)$ for a gamma-ray photon produced at distance $d$ from the black hole, using a BLR photon field built from four measured or scaled emission lines (Ly$\alpha$+NV, CIV, MgII, H$\beta$) superposed on a 1500 K blackbody continuum. The BLR is treated as a thin shell with inner and outer radii $0.9\,R_{\mathrm{BLR}}$ and $1.1\,R_{\mathrm{BLR}}$. The composite spectral model multiplies an intrinsic power-law, log-parabola, or cutoff power-law (with catalog parameters) by $\exp(-\tau_{\gamma\gamma})$ and by EBL attenuation; scanning $d$ then produces a test-statistic curve $\mathrm{TS}(d)$ whose rise or fall relative to the zero-opacity model yields either a best-fit distance or a lower limit. The pair-production threshold condition $\epsilon_s\epsilon_\gamma = 1$ for head-on collisions places the Ly$\alpha$ absorption feature at $E_{\gamma,\mathrm{obs}} \simeq 25\,\mathrm{GeV}/(1+z)$, which is why high-redshift sources are targeted.

What would settle it

Re-running the likelihood scan for 4FGL J0733.8+0455 with the intrinsic spectral index (and cutoff energy, where present) left free, instead of fixed to the catalog values, would settle whether the $4\sigma$ exclusion of $d<0.93\,R_{\mathrm{BLR}}$ and the $1.7\sigma$ absorption hint survive; if they weaken or vanish, the conclusion is an artifact of the assumed intrinsic spectrum.

Watch

Extended reading notes

Core claim

The central claim is that the GeV-emitting region of 4FGL J0733.8+0455 ($z=3.01$) is located at $d/R_{\mathrm{BLR}} = 0.95^{+0.09}_{-0.02}$ ($d = 0.19^{+0.018}_{-0.004}$ pc), with a lower limit $d \geq 0.93\,R_{\mathrm{BLR}}$ ($\geq 0.186$ pc), obtained from a likelihood scan over the distance $d$ of the emission zone. The test-statistic curve for this source drops abruptly for $d$ below $0.93\,R_{\mathrm{BLR}}$, excluding those distances at $\approx 4\sigma$, and then shows a peak at $d \approx 0.95\,R_{\mathrm{BLR}}$ for the power-law intrinsic spectrum, corresponding to a $1.7\sigma$ hint that the spectrum is better described with mild internal absorption than without. The paper stresses that this result is independent of the leptonic or hadronic emission mechanism, requiring only that the GeV production site lies within or near the BLR. For the remaining eight sources, no significant test-statistic variation with $d$ is found, which the authors attribute to limited photon statistics at the energies where the absorption feature would appear.

Load-bearing premise

The analysis assumes the intrinsic gamma-ray spectrum of each source is known from the 4FGL-DR4 catalog and that only its normalization changes as the emission-region distance is varied; if the true intrinsic spectrum is harder or contains a cutoff, the derived exclusion and the absorption hint could be different.

Editorial extensions

If this is right

  • If the central claim is correct, the GeV-emitting region of 4FGL J0733.8+0455 is inside the BLR, so the external-Compton scenario for this source is viable and the region is not beyond the BLR/dusty torus.
  • The 4σ lower limit $d \geq 0.93\,R_{\mathrm{BLR}}$ is a robust piece of evidence that the emission zone cannot be located deep inside the BLR for this source.
  • For the eight other sources, the lack of constraints means the search method is currently statistics-limited, not model-limited; additional exposure could convert non-detections into meaningful limits.
  • The paper's own forward-looking statement: intermediate-redshift ($z\sim1$–3) blazars with hard spectra, observed by Fermi-LAT and later CTAO, should show the absorption feature at higher energies ($\gtrsim6$–12 GeV) with better photon statistics, potentially yielding significant detections.
  • A corollary: in the same framework, any source whose spectrum shows no absorption feature is consistent with emission outside the BLR, so the technique can also set lower limits on the emission-region distance (as done here).

Reading between the lines

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

  • The 1.7σ hint is sensitive to the fixed intrinsic-spectrum assumption; if the 4FGL-DR4 power-law index is slightly off or a cutoff is present, the TS peak at $d\approx0.95\,R_{\mathrm{BLR}}$ could weaken or shift, so the quoted uncertainties should be read as conditional on that assumption.
  • The same procedure applied to a larger sample of $z\sim1$–3 hard-spectrum FSRQs could turn the single hint into a statistical measurement of the BLR location distribution for GeV emission, provided the intrinsic spectra are constrained by simultaneous multi-wavelength data.
  • The assumption of a single emission zone may be the dominant systematic: if GeV radiation actually comes from multiple zones (some inside, some outside the BLR), the TS($d$) curve would be a convolution of absorption profiles and the inferred $d$ would be biased toward the inner zone.
  • A testable extension: for Source 3, monitoring the optical/UV line luminosities over time and correlating with gamma-ray spectral changes could test whether the inferred $d$ varies with BLR line strength, as expected if absorption is real.
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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

4 major / 9 minor

Summary. This paper searches for signatures of internal gamma-gamma absorption of Fermi-LAT gamma-rays by the broad-line region (BLR) photon field in nine flat-spectrum radio quasars at z >= 3. The BLR target photon field is built from measured C IV / Mg II line luminosities (scaled to Ly-alpha+N V, Mg II, and H-beta using Finke 2016 ratios) plus a 1500 K blackbody continuum, using the BLR shell geometry and full-angle gamma-gamma cross-section from Boettcher & Els (2016). For each source, the authors extract Fermi-LAT spectra (MJD 54683-59794) with the composite model dN/dE = dN_intrinsic/dE x exp(-tau_gamma-gamma) x exp(-tau_EBL), using three intrinsic models (PL, LP, PLEC) whose shape parameters are fixed to 4FGL-DR4 catalog values, and they scan the emission-region distance d with only the normalization left free. Only Source 3 (4FGL J0733.8+0455, z = 3.01) shows significant TS variation with d: an abrupt drop at d around 0.93 R_BLR (Delta TS about -18, quoted as about 4 sigma), implying d >= 0.93 R_BLR (d >= 0.186 pc), and, for the power-law intrinsic model only, a TS maximum at d/R_BLR = 0.95 (+0.09, -0.02) with Delta TS about +3 (quoted as a 1.7 sigma hint of internal absorption). The remaining eight sources are unconstrained because of limited photon statistics above about 5 GeV.

Significance. If the main result survives scrutiny, the lower limit d >= 0.93 R_BLR for 4FGL J0733.8+0455 is a rare direct geometric constraint on the GeV emission site in a high-redshift FSRQ, and it is stated in falsifiable form in both R_BLR and pc units. The method has genuine strengths: the opacity is computed from independently measured emission-line luminosities rather than an average BLR template; the angle-dependent gamma-gamma optical depths are precomputed on a fine energy-distance grid for each source; full TS(d) curves are shown for all nine sources and three intrinsic models; and the paper explicitly discusses its limiting assumptions (line variability, one-zone geometry, and the degeneracy between intrinsic cutoffs and EBL/internal absorption). These features make the analysis easy to reproduce and extend. The significance is tempered by the modest statistics of the claimed 1.7 sigma hint and by the fact that the only quantitative constraint rests on the assumed intrinsic spectral shape; if the EBL-handling and internal-consistency issues raised below are resolved, this will be a solid contribution to the debate on where FSRQ gamma-rays are produced.

major comments (4)
  1. [§4, Eq. (4)] The intrinsic spectral parameters in Eq. (4) are taken from 4FGL-DR4, whose spectral fits characterize the observed photon spectrum at Earth; the standard Fermi-LAT catalog analysis does not include EBL absorption. Using the catalog shape as dN_intrinsic/dE and then multiplying by exp(-tau_EBL) therefore applies EBL attenuation twice at high energies. For z approximately 3, the EBL optical depth in the 6-30 GeV band is non-negligible (of order 0.2-1 in typical models such as the Saldana-Lopez et al. 2021 model adopted here), i.e., comparable to the internal-absorption effects that the analysis searches for. The common factor exp(-tau_EBL) cancels to first order in Delta TS = TS(d) - TS0, but the cancellation is incomplete: with only the normalization free, the re-fit forces agreement at low energies, where EBL is small, and leaves the catalog-shape steepness, which already includes some EBL softening, in place. The predicted high-energy spectrum is therefore systematically too steep, and the bias concentrates in exactly the bins that carry the Ly-alpha absorption signature of Source 3. This can shift both the location and the quoted roughly 4 sigma significance of the TS drop and can alter the +3 TS pile-up at d approximately 0.95 R_BLR. The stated agreement between TS0 and the 4FGL TS does not settle the issue, because a single global TS with a free normalization is insensitive to shape mismatches in low-statistics high-energy bins. The fix is to construct the intrinsic spectrum as the 4FGL-DR4 shape divided by exp(-tau_EBL), or equivalently to re-fit the spectral parameters with the full model containing both EBL and internal opacity; the Source 3 analysis should be redone with this correction.
  2. [§4] When varying d, only the normalization is left free; the spectral index, curvature, and cutoff energy are fixed at their 4FGL-DR4 values. The paper argues that the catalog parameters are determined by low-energy data where internal absorption is negligible and that freeing them would offer only marginal improvement, but this is asserted rather than tested. Since the central claim is a lower limit on d derived from the shape of the TS(d) curve, the relevant question is whether that curve, and not just the absolute TS, shifts when the intrinsic shape is allowed to change: a harder intrinsic index or a cutoff near the absorption feature could partially mimic or mask the internal-opacity signature, moving the exclusion boundary and the position of the best-fit pile-up. A robustness test in which the photon index (and the cutoff energy for PLEC) is left free in the scan, or at least varied by +/-1 sigma around the catalog value, with the resulting d/R_BLR limits and Delta TS significances reported, is needed. This is especially important given the paper's own acknowledgment in Section 5 of the degeneracy between internal absorption, EBL absorption, and an intrinsic spectral cutoff.
  3. [§2.2–§3] The systematic uncertainty in the emission-line luminosities is acknowledged but never propagated into the quoted constraints. Section 2.2 notes that emission-line luminosities can vary by a factor of 3-4 and that the adopted values are single-epoch measurements (Mg II from Burke et al. 2024 for Source 3; C IV from Paliya et al. 2021 for the rest) assumed to represent time averages over the 14-year Fermi-LAT window. Since tau_gamma-gamma scales approximately linearly with the line energy densities in Eq. (1), a factor 3-4 change in the Ly-alpha+NV luminosity of Source 3 would directly rescale the opacity and would shift the d at which the TS drop occurs as well as the size of the drop. The quoted lower limit d >= 0.93 R_BLR and the 1.7 sigma hint therefore carry an unquantified systematic that is much larger than the listed +/-0.02 to 0.09 R_BLR statistical uncertainties. The paper should state how the central limit and the hint significance respond to, e.g., factor-2 and factor-4 increases or decreases of all line luminosities, and should quote a corresponding systematic error on d/R_BLR.
  4. [§4 vs. §5] The paper quotes two different lower limits for the same source: Section 4 concludes d >= 0.88 R_BLR, while Section 5, the abstract, and the conclusions give d >= 0.93 R_BLR. No explanation is given for the difference (different intrinsic models, different confidence thresholds, or a refined analysis). In addition, Section 5 describes both the roughly 4 sigma TS drop and the 1.7 sigma pile-up only in the case of the power-law intrinsic model, leaving it unclear whether the headline constraint holds for the LP and PLEC models as well. These are internal inconsistencies in the central result and must be resolved: the text should quote, for each of the three intrinsic models, the adopted lower limit and the corresponding confidence level, and a single consistent value should be carried through the abstract, body, and conclusions.
minor comments (9)
  1. [§5] The 1.7 sigma significance quoted for the global TS maximum at d approximately 0.95 R_BLR does not account for the scan over a dense grid of d values (a look-elsewhere effect); the effective number of independent d values should be estimated from the correlation length of the TS curve and the post-trials significance reported.
  2. [§4] The claimed agreement between the baseline TS0 values and the 4FGL-DR4 TS values is stated verbally but never quantified; a small table or list of TS0 for the three models would make the verification reproducible.
  3. [§2.2] Typo: the derived emission line luminosities represent represent time-averaged values (duplicated word).
  4. [Fig. 1(b)] The five tau_gamma-gamma(E,d) curves in Fig. 1(b) are not labeled with the corresponding gamma-ray energies; a legend or inline labels would make the figure decipherable on its own.
  5. [References] The Blazejowski et al. (2000) entry is rendered as B la dot zejowski with corrupted characters; fix the encoding in the reference list.
  6. [§3] The statement that the choice of R1 = 0.9 R_BLR and R2 = 1.1 R_BLR has a negligible impact is not demonstrated; since the derived constraint d >= 0.93 R_BLR lies immediately outside R1, a short sensitivity test with, e.g., R1 = 0.8-1.0 R_BLR would strengthen the claim.
  7. [§3] The adoption of xi_BLR = 20% as the smallest multiple of 10 satisfying the positivity constraint is ad hoc; the argument that the narrow emission lines dominate the opacity at the Ly-alpha-feature energies is plausible, but a figure showing that the TS(d) curve is insensitive to xi_BLR in the 10-30% range would put this on firmer footing.
  8. [§5] The dismissal of the Source 5 PL-model Delta TS >= 4 variation because the PL model exhibits the lowest TS among the three models needs one more sentence of justification; a poor absolute fit does not automatically invalidate a relative TS variation with d.
  9. [Fig. 2 caption] Minor typo: The models account also for EBL absoprtion should read absorption.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the internal gamma-gamma opacity is computed from independent BLR line-luminosity inputs and a published BLR model, then compared with Fermi-LAT data via a likelihood scan over d; the adopted catalog intrinsic spectrum is a modeling assumption rather than a fitted prediction.

full rationale

The paper's derivation chain is not circular. The internal opacity exp(-tau_gamma-gamma) is computed in Section 3 from BLR line luminosities (Table 2) derived from archival C IV/Mg II measurements and Finke (2016) line ratios, combined with a BLR geometry and accretion-disk luminosity from Paliya et al. (2020); none of these inputs are fit to the Fermi-LAT data used in the d-constraint. In Section 4 the likelihood scan varies only the distance d, with the overall normalization free, and compares the resulting model to the observed photon distribution. The constraint d/R_BLR = 0.95(+0.09,-0.02) for Source 3 is therefore a comparison of an independently computed absorption prediction against the gamma-ray data, not a fit of a quantity that is defined by the same data. The only input taken from the same Fermi-LAT catalog is the assumed shape of the intrinsic spectrum; because only the normalization is varied, the intrinsic shape is an adopted assumption, and an incorrect shape would bias the model, but that is a modeling limitation, not circular forcing. The Boettcher & Els (2016) code is a self-citation by co-author Boettcher, but it is a published, independent radiative-transfer calculation, and the paper states the shell-radius choices R1=0.9 R_BLR, R2=1.1 R_BLR have negligible impact on results. The skeptical concern about double-counting EBL if the 4FGL-DR4 shape is already EBL-attenuated is a potential physical-modeling issue for the baseline model, not a reduction of the prediction to its inputs. Overall, the central claim does not reduce by construction to a fit or to an unverified self-citation chain.

Assumptions & free parameters 3 free parameters · 5 assumptions · 0 invented entities

The model relies on standard BLR geometry and scaling relations, plus an ad hoc covering factor and fixed intrinsic spectral shapes. No new particles, forces, or dimensions are introduced.

free parameters (3)
  • ξBLR (BLR covering factor) = 0.2
    Chosen in Section 3 as the smallest multiple of 10 that keeps the continuum energy density non-negative for all sources. Authors claim minor effect since lines dominate the opacity, but it sets the total BLR energy density and the continuum normalization.
  • BLR continuum blackbody temperature T = 1500 K
    Fixed in Section 3 for the blackbody continuum component of the BLR template; the authors note 1000 K is an alternative and claim minor impact.
  • BLR shell radii R1 and R2 = R1=0.9 R_BLR, R2=1.1 R_BLR
    Adopted from Böttcher & Els (2016) in Section 3; authors state the exact choice has negligible impact on results.
assumptions (5)
  • domain assumption The BLR photon field dominates both gamma-ray production and gamma-gamma absorption for all sample sources.
    Stated in Section 1 and 2.2; if the GeV emission region is far outside the BLR, no internal absorption features are expected, as acknowledged in Section 5.
  • domain assumption The BLR is a thin shell with R1=0.9 R_BLR, R2=1.1 R_BLR and the opacity code performs full angle integration.
    Section 3, following Böttcher & Els (2016).
  • domain assumption Emission line luminosities derived from C IV measurements and Finke (2016) ratios are representative time-averaged values over the Fermi mission.
    Section 2.2 notes line luminosities vary by factors of 3-4, but the absence of multi-epoch optical data leads the authors to assume time-averaged values.
  • domain assumption The intrinsic gamma-ray spectral shape is fixed to 4FGL-DR4 catalog values, with only normalization free when scanning d.
    Section 4, load-bearing for the TS(d) curves and the 4σ exclusion of small distances.
  • domain assumption The BLR radius scales as R_BLR = 0.1 (L_D,46)^1/2 pc.
    Used in Section 3 to convert luminosities to energy densities and distances; adopted from Baskin & Laor (2018).

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Cite this review

Pith. "Pith review of Searching for Internal Absorption Signatures in High-Redshift Blazars." pith.science (2026). https://pith.science/paper/546SEHGB

@misc{pith2026250204154,
  author       = {Pith},
  title        = {Pith review of: Searching for Internal Absorption Signatures in High-Redshift Blazars},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/546SEHGB}},
  note         = {Machine review of arXiv:2502.04154}
}
read the original abstract

The gamma-ray emission from Flat Spectrum Radio Quasars (FSRQs), a sub-class of blazars, is believed to be generated through interactions of high-energy leptons and/or hadrons in the jet with the ambient photon fields, including those from the accretion disk, the broad line region (BLR), and the dusty torus. However, these same photon fields can also attenuate gamma-rays through internal photon-photon (gamma-gamma) absorption, imprinting characteristic spectral features. Investigating the internal absorption is crucial for unraveling the complex structure of FSRQs and constraining the poorly known location of the gamma-ray emission region. In this study, we select a sample of gamma-ray detected FSRQs with high redshift (z >= 3), to search for absorption features appearing at lower photon energies due to a substantial redshift. We extract the Fermi-LAT gamma-ray spectra of these sources and perform physical modeling using a detailed gamma-gamma opacity model, assuming that the BLR photon field dominates the absorption and focusing on the energy range ~25 GeV/(1+z), where the absorption feature due to Ly{\alpha} photons is expected. Our analysis reveals a hint of internal absorption for one source (the lowest redshift object in our sample, z~3) and provides constraints on the location of its gamma-ray emitting region along the jet. For the remaining, higher-redshift sources, the limited photon statistics prevent a reliable detection of internal opacity features.

Figures

Figures reproduced from arXiv: 2502.04154 by the authors.

Figure 1
Figure 1. (a) Target photon field template for the Source 3, shown in the ϵnϵ representation, with ϵ = hν/mec 2 being the dimensionless target photon energy, and nϵ being the number density of target photons per unit of dimensionless energy interval. (b) Optical depth of internal γ–γ absorption τγ−γ depending on the distance d, computed for Source 3 for five different γ-ray energies. Here, Rin = R1 = 0.9 RBLR, Rout = R2 = 1.1… view at source ↗
Figure 2
Figure 2. The Fermi-LAT SEDs for all nine high-z sources in our sample, obtained for the baseline model where the internal γ–γ opacity is set to zero. The data points obtained for each of the three intrinsic spectral model, PL, LP, and PLEC, are shown in blue, red and green respectively. The corresponding curves represent the best fits obtained for each model. The models account also for EBL absoprtion, using the model from S… view at source ↗
Figure 3
Figure 3. Behavior of TS as a function of the distance from the SMBH d for all nine high-z sources in our sample. Three TS curves are shown, with blue, green and red diamonds representing the power-law, power-law with an exponential cutoff and logparabola intrinsic spectrum models, respectively. The shaded regions visualize the 2σ (TS-TS0=4) confidence level. responding to a deviation of TS from the best-fit value by 1 (1σ le… view at source ↗

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Works this paper leans on

42 extracted references · 10 canonical work pages

  1. [1]

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

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

  2. [2]

    write newline

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

  3. [3]

    Blazars at the Cosmic Dawn

    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...

    work page Pith review arXiv 2021

  4. [4]

    M., & Brown , A

    Acharyya , A., Chadwick , P. M., & Brown , A. M. 2021, , 500, 5297, 10.1093/mnras/staa3483

    work page doi:10.1093/mnras/staa3483 2021

  5. [5]

    F., Argudo-Fern \'a ndez , M., et al

    Almeida , A., Anderson , S. F., Argudo-Fern \'a ndez , M., et al. 2023, , 267, 44, 10.3847/1538-4365/acda98

    doi:10.3847/1538-4365/acda98 2023

  6. [6]

    2013, arXiv e-prints, arXiv:1303.3514

    Atwood , W., Albert , A., Baldini , L., et al. 2013, arXiv e-prints, arXiv:1303.3514. 1303.3514

    arXiv 2013

  7. [7]

    B., Abdo , A

    Atwood , W. B., Abdo , A. A., Ackermann , M., et al. 2009, , 697, 1071, 10.1088/0004-637X/697/2/1071

    doi:10.1088/0004-637x/697/2/1071 2009

  8. [8]

    H., Lott , B., & The Fermi-LAT collaboration

    Ballet , J., Bruel , P., Burnett , T. H., Lott , B., & The Fermi-LAT collaboration . 2023, arXiv e-prints, arXiv:2307.12546, 10.48550/arXiv.2307.12546

    arXiv doi:10.48550/arxiv.2307.12546 2023

Show all 42 references
  1. [9]

    2018, , 474, 1970, 10.1093/mnras/stx2850

    Baskin , A., & Laor , A. 2018, , 474, 1970, 10.1093/mnras/stx2850

    2018 doi

  2. [10]

    B a \.z ejowski , M., Sikora , M., Moderski , R., & Madejski , G. M. 2000, , 545, 107, 10.1086/317791

    2000 doi

  3. [11]

    D., & Marscher , A

    Bloom , S. D., & Marscher , A. P. 1996, , 461, 657, 10.1086/177092

    1996 doi

  4. [12]

    2016, , 821, 102, 10.3847/0004-637X/821/2/102

    B \"o ttcher , M., & Els , P. 2016, , 821, 102, 10.3847/0004-637X/821/2/102

    2016 doi

  5. [13]

    2013, , 768, 54, 10.1088/0004-637X/768/1/54

    B \"o ttcher , M., Reimer , A., Sweeney , K., & Prakash , A. 2013, , 768, 54, 10.1088/0004-637X/768/1/54

    2013 doi

  6. [14]

    J., Liu , X., & Shen , Y

    Burke , C. J., Liu , X., & Shen , Y. 2024, , 527, 5356, 10.1093/mnras/stad3592

    2024 doi

  7. [15]

    2018, , 477, 4749, 10.1093/mnras/sty887

    Costamante , L., Cutini , S., Tosti , G., Antolini , E., & Tramacere , A. 2018, , 477, 4749, 10.1093/mnras/sty887

    2018 doi

  8. [16]

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

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

    2011 doi

  9. [17]

    2003, , 339, 1081, 10.1046/j.1365-8711.2003.06255.x

    D'Elia , V., Padovani , P., & Landt , H. 2003, , 339, 1081, 10.1046/j.1365-8711.2003.06255.x

    2003

  10. [18]

    D., Cerruti , M., Lott , B., Boisson , C., & Zech , A

    Dermer , C. D., Cerruti , M., Lott , B., Boisson , C., & Zech , A. 2014, , 782, 82, 10.1088/0004-637X/782/2/82

    2014 doi

  11. [19]

    D., Schlickeiser , R., & Mastichiadis , A

    Dermer , C. D., Schlickeiser , R., & Mastichiadis , A. 1992, , 256, L27

    1992

  12. [20]

    Dmytriiev , A., B \"o ttcher , M., & Machipi , T. O. 2023, , 949, 28, 10.3847/1538-4357/acc57b

    2023 doi

  13. [21]

    Finke , J. D. 2016, , 830, 94, 10.3847/0004-637X/830/2/94

    2016 doi

  14. [22]

    1998, , 299, 433, 10.1046/j.1365-8711.1998.01828.x

    Fossati , G., Maraschi , L., Celotti , A., Comastri , A., & Ghisellini , G. 1998, , 299, 433, 10.1046/j.1365-8711.1998.01828.x

    1998

  15. [23]

    J., Hewett , P

    Francis , P. J., Hewett , P. C., Foltz , C. B., et al. 1991, , 373, 465, 10.1086/170066

    1991 doi

  16. [24]

    2017, , 469, 255, 10.1093/mnras/stx806

    Ghisellini , G., Righi , C., Costamante , L., & Tavecchio , F. 2017, , 469, 255, 10.1093/mnras/stx806

    2017 doi

  17. [25]

    2010, , 402, 497, 10.1111/j.1365-2966.2009.15898.x

    Ghisellini , G., Tavecchio , F., Foschini , L., et al. 2010, , 402, 497, 10.1111/j.1365-2966.2009.15898.x

    2010

  18. [26]

    H. E. S. S. Collaboration , Abdalla , H., Adam , R., et al. 2019, , 627, A159, 10.1051/0004-6361/201935704

    2019 doi

  19. [27]

    M., Nalewajko , K., et al

    Hayashida , M., Madejski , G. M., Nalewajko , K., et al. 2012, , 754, 114, 10.1088/0004-637X/754/2/114

    2012 doi

  20. [28]

    Maiolino , R., Salvati , M., Marconi , A., & Antonucci , R. R. J. 2001, , 375, 25, 10.1051/0004-6361:20010808

    2001 doi

  21. [29]

    1993, , 269, 67, 10.48550/arXiv.astro-ph/9302006

    Mannheim , K. 1993, , 269, 67, 10.48550/arXiv.astro-ph/9302006

    1993 doi arXiv

  22. [30]

    Mannheim , K., & Biermann , P. L. 1992, , 253, L21

    1992

  23. [31]

    1992, , 397, L5, 10.1086/186531

    Maraschi , L., Ghisellini , G., & Celotti , A. 1992, , 397, L5, 10.1086/186531

    1992 doi

  24. [32]

    J., Engel , R., Rachen , J

    M \"u cke , A., Protheroe , R. J., Engel , R., Rachen , J. P., & Stanev , T. 2003, Astroparticle Physics, 18, 593, 10.1016/S0927-6505(02)00185-8

    2003 doi

  25. [33]

    B., & Korycansky , D

    Oke , J. B., & Korycansky , D. G. 1982, , 255, 11, 10.1086/159797

    1982 doi

  26. [34]

    Paliya , V. S. 2015, , 808, L48, 10.1088/2041-8205/808/2/L48

    2015 doi

  27. [35]

    S., Ajello , M., Cao , H

    Paliya , V. S., Ajello , M., Cao , H. M., et al. 2020, , 897, 177, 10.3847/1538-4357/ab9c1a

    2020 doi

  28. [36]

    S., Dom \' nguez , A., Ajello , M., Olmo-Garc \' a , A., & Hartmann , D

    Paliya , V. S., Dom \' nguez , A., Ajello , M., Olmo-Garc \' a , A., & Hartmann , D. 2021, , 253, 46, 10.3847/1538-4365/abe135

    2021 doi

  29. [37]

    2010, , 717, L118, 10.1088/2041-8205/717/2/L118

    Poutanen , J., & Stern , B. 2010, , 717, L118, 10.1088/2041-8205/717/2/L118

    2010 doi

  30. [38]

    G., et al

    Saldana-Lopez , A., Dom \' nguez , A., P \'e rez-Gonz \'a lez , P. G., et al. 2021, , 507, 5144, 10.1093/mnras/stab2393

    2021 doi

  31. [39]

    C., & Rees , M

    Sikora , M., Begelman , M. C., & Rees , M. J. 1994, , 421, 153, 10.1086/173633

    1994 doi

  32. [40]

    2013, , 435, L24, 10.1093/mnrasl/slt087

    Tavecchio , F., Pacciani , L., Donnarumma , I., et al. 2013, , 435, L24, 10.1093/mnrasl/slt087

    2013 doi

  33. [41]

    2017, in International Cosmic Ray Conference, Vol

    Wood , M., Caputo , R., Charles , E., et al. 2017, in International Cosmic Ray Conference, Vol. 301, 35th International Cosmic Ray Conference (ICRC2017), 824. 1707.09551

    2017 arXiv

  34. [42]

    2015, , 807, 51, 10.1088/0004-637X/807/1/51

    Zhang , J., Xue , Z.-W., He , J.-J., Liang , E.-W., & Zhang , S.-N. 2015, , 807, 51, 10.1088/0004-637X/807/1/51

    2015 doi

Pith tools

Reviewed August 8, 2026 · model on record in the stance chip above.