Pith. sign in

REVIEW 4 major objections 5 minor 64 references

Longtime Monitoring of TeV Radio Galaxies with HAWC

T0 review · 4 major / 5 minor · reviewed 2026-08-06 · deepseek-v4-flash

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

Pith's one-line read Over 7.5 years of monitoring, the radio galaxy M87 is detected at 5.21 sigma in TeV gamma rays, with a power-law spectrum extending to 26.5 TeV—the first low-activity-state emission above 10 TeV.

desk verdict A real 5-sigma M87 detection and a useful long-baseline TeV spectrum sit inside a monitoring paper whose variability claims are largely artifacts of a 2-sigma selection cut. read the letter →

arxiv 2506.16031 v1 pith:4F3CVWDQ submitted 2025-06-19 astro-ph.HE

R. Alfaro , C. Alvarez , E. Anita-Rangel , J.C. Arteaga-Velázquez , D. Avila Rojas , H.A. Ayala Solares , R. Babu , P. Bangale
show 80 more authors
E. Belmont-Moreno A. Bernal K.S. Caballero-Mora T. Capistrán A. Carramiñana F. Carreón S. Casanova U. Cotti J. Cotzomi S. Coutiño de León E. De la Fuente D. Depaoli P. Desiati N. Di Lalla R. Diaz Hernandez M.A. DuVernois J.C. Díaz-Vélez K. Engel T. Ergin C. Espinoza N. Fraija S. Fraija J.A. García-González F. Garfias A. Gonzalez Muñoz M.M. González J.A. González J.A. Goodman S. Groetsch J.P. Harding I. Herzog D. Huang F. Hueyotl-Zahuantitla A. Iriarte S. Kaufmann D. Kieda A. Lara J. Lee H. León Vargas A.L. Longinotti G. Luis-Raya K. Malone O. Martinez J. Martínez-Castro J.A. Matthews P. Miranda-Romagnoli J.A. Morales-Soto E. Moreno M. Mostafá M. Najafi A. Nayerhoda L. Nellen N. Omodei M. Osorio-Archila E. Ponce Y. Pérez Araujo E.G. Pérez-Pérez C.D. Rho A. Rodriguez Parra D. Rosa-González M. Roth H. Salazar A. Sandoval M. Schneider J. Serna-Franco Y. Son R.W. Springer O. Tibolla K. Tollefson I. Torres R. Torres-Escobedo E. Varela L. Villaseñor X. Wang Z. Wang I.J. Watson H. Wu S. Yu H. Zhou C. de León
This is my paper · ORCID
classification astro-ph.HE
keywords AGNradiogalaxiesVHEgammarayslightcurveM87HAWCTeVemissionactivegalacticnuclei
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 that the radio galaxy M87 has been emitting teraelectronvolt (TeV) gamma rays steadily enough that a 7.5-year dataset detects it with 5.21 $\sigma$ significance. The emission follows a simple power law with spectral index $\alpha = 2.53 \pm 0.29$ and a flux at 1 TeV of $(7.09 \pm 1.24)\times10^{-13}\,\mathrm{cm^{-2}\,s^{-1}\,TeV^{-1}}$, reaching up to 26.5 TeV. That makes this the first observation of M87 above 10 TeV in a low-activity state, a regime previously seen only during flares. The same monitoring marginally detects 3C 264 (about 4 $\sigma$), does not firmly detect NGC 1275 or IC 310, and finds that the cumulative significance of all four sources grows like a variable gamma-ray active galaxy rather than a steady source. If correct, this shows that quiescent radio galaxies can accelerate particles to tens of TeV and supports long-term wide-field monitoring to catch enhanced states.

What carries the argument

The central object is a set of daily, weekly, and monthly light curves combined with a cumulative-significance growth curve, all computed from PASS 5 reconstructed wide-field data under a point-source hypothesis with a power-law spectral model corrected for extragalactic background light. This machinery converts the long, high-duty-cycle dataset into a detection significance, an integrated spectrum, a maximum-energy estimate, and a temporal picture of when each galaxy's emission rose above the 2-sigma threshold. The cumulative-significance curve, compared with the Crab Nebula and Markarian 421, is what carries the argument that radio galaxies behave like variable active galaxies rather than steady sources.

What would settle it

Recompute the daily M87 fluxes with the same point-source power-law hypothesis used for the integrated spectrum, without omitting sub-2-sigma points, and compare the exposure-weighted mean daily flux to the fitted normalization; if the discrepancy persists, the light-curve-based onset claims are not supported. A separate check would test whether the 26.5 TeV photons survive a stricter event selection.

Watch

Extended reading notes

Core claim

The central claim is that, over 2141 days of nearly uninterrupted monitoring, M87 is detected in TeV gamma rays with a significance of 5.21 $\sigma$, and its integrated spectrum is a power law with $\alpha = 2.53 \pm 0.29$ and normalization $(7.09 \pm 1.24)\times10^{-13}\,\mathrm{cm^{-2}\,s^{-1}\,TeV^{-1}}$ at 1 TeV. The maximum photon energy reaches 26.5 TeV at the 1 $\sigma$ level and 15.6 TeV at the 3 $\sigma$ level, and the authors state this is the first time emission above 10 TeV has been seen from M87 in a low-activity state; previously such energies appeared only during the 2005 flare. They further claim that 3C 264 is marginally detected at 3.99 $\sigma$, that NGC 1275 and IC 310 are not detected, that weekly light curves indicate enhanced steady TeV emission beginning in 2019 for M87 and in 2018 for 3C 264, and that the cumulative significance curves of the four radio galaxies resemble a variable source such as Markarian 421 rather than a steady one like the Crab Nebula.

Load-bearing premise

The variability and onset claims rest on treating only 2-sigma-excess flux points in the light curves as real emission, while the paper itself notes the daily fluxes exceed the integrated long-term spectrum by up to two orders of magnitude; if that mismatch is not resolved, the enhanced-emission interpretation lacks support.

Editorial extensions

If this is right

  • M87's low-activity state is not dark: it produces photons up to 26.5 TeV, so quiescent radio galaxies can host particle acceleration to tens of TeV, not only during flares.
  • The first low-state observation above 10 TeV means that spectral cutoffs inferred from earlier low-state data cannot be assumed to apply at these energies.
  • The elongated excess between NGC 1275 and IC 310, if real, points toward IC 310 or the interposed radio galaxy CR 15 rather than NGC 1275, whose spectrum is known to cut off near 400–500 GeV.
  • The weekly-scale enhanced emission in M87 from 2019 onward gives a specific time window for multi-messenger follow-up during enhanced states.
  • The resemblance to Markarian 421 supports unification schemes in which radio galaxies are misaligned BL Lac objects, implying that continued monitoring should reveal flaring episodes rather than steady emission.

Reading between the lines

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

  • A different reading of the same data is possible once the paper's own caveat is taken seriously: the daily fluxes are up to two orders of magnitude higher than the integrated spectrum, so until that discrepancy is resolved, the claimed onset of enhanced steady emission in 2019/2018 should be treated as tentative.
  • The NGC 1275–IC 310 region could be settled by a joint likelihood fit that includes all three candidate sources; if CR 15 contributes, it would become a new TeV-emitting radio galaxy candidate.
  • One concrete extension is to compare the enhanced weekly states with contemporaneous neutrino alerts or radio/X-ray jet activity; if correlations appear, radio-galaxy monitoring could become a practical tool for multi-messenger astronomy.
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

4 major / 5 minor

Summary. The paper reports a 2141-day HAWC (PASS 5) monitoring campaign of four TeV-emitting radio galaxies: M87, NGC 1275, 3C 264, and IC 310. The authors find a 5.21σ detection of M87, fit its integrated spectrum with a simple power law of index α = 2.53 ± 0.29 and normalization (7.09 ± 1.24) × 10^-13 cm^-2 s^-1 TeV^-1 at 1 TeV, and estimate a maximum photon energy of 26.5 TeV at 1σ confidence. They report a marginal 3.99σ excess for 3C 264 and no significant detection of NGC 1275 or IC 310. Daily, weekly, and monthly light curves are presented, and the paper interprets an increased number of >2σ flux points starting in 2019 (M87) and 2018 (3C 264) as evidence of enhanced steady TeV emission. The cumulative significance curves are compared with those of the Crab Nebula and Mrk 421 to argue that the radio galaxies behave like a variable gamma-ray source.

Significance. If the M87 detection and spectrum are robust, this is a valuable long-term TeV measurement of a low-state radio galaxy with the largest temporal coverage to date, complementing IACT and LHAASO results. The spectral parameters and the reported >10 TeV reach in a low state would be of genuine interest for jet and particle-acceleration models, and the paper demonstrates HAWC's monitoring capability for extragalactic sources. However, the paper's variability claims rest on a selective light-curve presentation that is not statistically justified, and the cumulative-significance comparison with Mrk 421 is qualitative. The central detection and spectrum may survive revision, but the interpretation as evidence of enhanced steady emission currently does not.

major comments (4)
  1. [§4, Figures 3–6] The claim that M87 and 3C 264 show 'high flux increments at daily time scales' is unsupported because the light curves display only fluxes with significance greater than 2σ as black points. For a source with a total significance of 5.21σ over 2141 days, the per-day significance of a steady signal is roughly 5.21/√2141 ≈ 0.11σ, so the daily flux uncertainty is about 9 times the average flux. A 2σ threshold therefore selects upward fluctuations of roughly 20 times the long-term average flux, which is exactly the order of magnitude of the reported daily fluxes (≈10^-11 cm^-2 s^-1) compared with the integral of the time-averaged spectrum (≈4.6 × 10^-13 cm^-2 s^-1 above 1 TeV). The selected black points are therefore biased high and cannot be interpreted as evidence of flaring or of enhanced steady emission. The authors should present unbiased light curves that include upper limits and all flux measurements (or at least the gray points with their uncertainties), and quantify variability using a metric such as excess variance or a likelihood-ratio test against a constant-flux model.
  2. [§4, daily 3C 264 excess] The statement that 3C 264 shows '>70 days' with significance greater than 2σ against an expected '∼59 days' of background fluctuations is not a valid statistical comparison. For a Gaussian background, the probability of a positive 2σ fluctuation is about 2.3% per day, giving an expectation of about 49 days over 2141 days, not 59; moreover, the same selection bias applies to 3C 264 as to M87, since the source is only marginally detected and its per-day flux uncertainty is large. The excess of black points is therefore an artifact of the threshold plus positive fluctuations, not evidence of physical variability. The authors should provide a proper trial-corrected significance calculation using all daily measurements, not only the >2σ subset.
  3. [§4, Figure 7] The conclusion that the cumulative significance behavior of the radio galaxies 'resembles that of a variable source such as Markarian 421' is not supported by any quantitative test. For a steady source, the cumulative significance is expected to grow approximately as the square root of the observation time, while for a variable source it grows in steps; the plotted curves for faint or non-detected sources are dominated by background fluctuations, so a qualitative resemblance to Mrk 421 is not meaningful. The authors should either provide a statistical measure of the difference between the cumulative-significance curves (e.g., a chi-square or KS-type test against the steady-source hypothesis) or soften this claim.
  4. [§3 and §5, maximum energy claim] The abstract and conclusions state that this is the first observation of emission above 10 TeV from M87 in a low-activity state, but the evidence presented is the maximum energy 'estimated' as 26.5 TeV at 1σ confidence using the method of Abeysekara et al. (2017c), not a direct detection of significant flux in energy bins above 10 TeV. The authors should clarify whether the 26.5 TeV value comes from a spectral-unfolding or a photon-energy estimator, and should show the energy-binned significance or the number of events above 10 TeV to justify the claim that emission above 10 TeV is actually observed.
minor comments (5)
  1. [§4] There is a typo in 'This mean that the emission observed from M87 by HAWC is in the 16−26 TeV energy range'; it should be 'This means', and the sentence should more precisely refer to the maximum photon energy rather than the energy range of all detected emission.
  2. [Table 1] The column header 'Flux at 1 TeV' is misleading for rows with pivot energy E0 = 100 GeV or E0 = 300 GeV; the normalization is at the pivot energy, not at 1 TeV. Please relabel the column or convert all normalizations to a common pivot energy.
  3. [§3] The spectral fit reports only statistical uncertainties on α and the normalization; the authors should quote the relevant HAWC systematic uncertainties, which typically affect the flux normalization by tens of percent, especially in the context of comparing with IACT measurements.
  4. [§5] The statement that this is 'the first, uninterrupted very long term TeV monitoring of radio galaxies that is not biased to a particular activity state' is too strong: HAWC's exposure is not continuous at all times and the light-curve presentation is itself biased by the 2σ selection. Please qualify the claim.
  5. [References] There are duplicate or inconsistent reference entries (e.g., 'Ahnen et al. 2017' appears twice with different author lists) that should be consolidated.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the M87 detection, spectrum, and long-term monitoring are direct forward-modeled measurements whose inputs (spectral hypotheses, calibration methods) come from independent prior work, not from the claimed outputs.

full rationale

This is an observational data-analysis paper, not a derivation chain. The central claims—M87 detected at 5.21 sigma, a power-law spectrum with alpha = 2.53 +/- 0.29 and normalization (7.09 +/- 1.24)e-13 cm^-2 s^-1 TeV^-1, maximum photon energy 26.5 TeV at 1 sigma—are obtained by forward-modeling HAWC event counts against a background model and fitting the resulting excess. No quoted quantity is defined in terms of the claimed result. The spectral hypotheses used to generate significance maps and light curves (SPL for M87, IC 310, 3C 264; PLEC for NGC 1275) are taken from the prior independent IACT observations listed in Table 1 (H.E.S.S., MAGIC, VERITAS), not from a fit to the HAWC output, so the source is not being used to define its own detection model. The methodological citations (Abeysekara et al. 2017b,c,d; Albert et al. 2024) are standard instrument-calibration and statistical procedures and are not load-bearing self-citations. The paper's own observation that the selected daily fluxes are up to two orders of magnitude above the integrated spectrum (Section 4) is a possible selection-bias or normalization inconsistency, but that is a statistical/correctness concern, not a circular one: the >2-sigma display cut is a selection rule, not a fitted parameter renamed as a prediction, and the discrepancy is explicitly reported rather than silently built into the result. No equation in the paper reduces to its own input, and no alternative is ruled out solely by a self-citation. Honest non-finding: no significant circularity.

Assumptions & free parameters 1 free parameters · 3 assumptions · 0 invented entities

The paper does not introduce new physical entities. It relies on standard HAWC analysis assumptions: the expected source spectra from prior IACT observations, an EBL attenuation model, and point-source morphology. The pivot energy for the spectral fit is chosen to reduce parameter correlation, a conventional choice.

free parameters (1)
  • Pivot energy E0 = 12 TeV
    Chosen to minimize correlation between spectral fit parameters; this choice affects the extrapolated flux at 1 TeV via the power law.
assumptions (3)
  • domain assumption M87, IC 310, and 3C 264 gamma-ray emission follows a simple power law (Eq. 1); NGC 1275 follows a power law with exponential cutoff (Eq. 2).
    Section 3, used to define the significance maps and light curves; based on prior IACT observations, not independently verified in this work.
  • domain assumption EBL attenuation is described by the Franceschini et al. (2008) model.
    Used for spectrum de-absorption; alternative EBL models would shift the intrinsic spectrum.
  • domain assumption The sources are point-like for the HAWC analysis.
    Used in likelihood fitting; HAWC PSF is about 0.5-1 degree, and M87 is point-like at this resolution.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Longtime Monitoring of TeV Radio Galaxies with HAWC." pith.science (2026). https://pith.science/paper/4F3CVWDQ

@misc{pith2026250616031,
  author       = {Pith},
  title        = {Pith review of: Longtime Monitoring of TeV Radio Galaxies with HAWC},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/4F3CVWDQ}},
  note         = {Machine review of arXiv:2506.16031}
}
abstract

We present the monitoring of the TeV-emitting radio galaxies M87, NGC~1275, 3C~264, and IC~310 with the High Altitude Water Cherenkov Observatory (HAWC) over a period of approximately $7.5$ years. The analysis includes light curves at daily, weekly and monthly time scales for the four sources. We report the detection of gamma-ray emission from M87 with a significance exceeding 5$\sigma$. Due to its significant detection, this work reports the integrated TeV spectrum of M87 from the longest temporal coverage up to date. The source is well described as a point-like source modeled by a power law spectrum with spectral index $\alpha = 2.53\pm0.29$ and a flux of $(7.09\pm 1.24)\times10^{-13}$ $\rm{cm}^{-2}\,{s}^{-1}\,{TeV}^{-1}$ at $1\,\rm{TeV}$. The maximum energy of the detected emission in M87, at 1$\sigma$ confidence level (C.L.), reaches 26.5 TeV. HAWC's observation of M87 reveals a low flux spectrum for the longest observation to date of this radio galaxy. 3C~264 is marginally detected with a significance slightly below 4$\sigma$, while NGC~1275 and IC~310 are not detected. The weekly light curves show an increased number of fluxes above $2\sigma$ for M87 starting in 2019, and for 3C~264 starting in 2018, which can be interpreted as the moment for which these sources start to exhibit an enhanced steady TeV emission. Overall, in the four radio galaxies, the cumulative significance over time indicates a behavior that resembles that of a gamma-ray variable active galaxy, such as the blazar Markarian 421. This supports the importance of monitoring radio galaxies to identify periods of higher activity and flares, enabling further multi-messenger studies.

Figures

Figures reproduced from arXiv: 2506.16031 by the authors.

Figure 1
Figure 1. Significance maps obtained with the Neural Network energy estimator. Top left: M87 is detected with a significance of 5.21σ. Top right: 3C 264 is marginally detected with a significance of 3.99 σ. Bottom left: NGC 1275 is not detected, with a maximum significance of 2.21σ at the source position. Bottom right: IC 310 is not detected, with a significance of 1.34σ at the source position. Difference between bottom maps … view at source ↗
Figure 2
Figure 2. Measured flux (solid black points) and best-fit spectrum (dashed line) of M87. Downward arrows represent upper limits at a 95% confidence level. The fitted spectrum is calculated by assuming a simple power law and fixing the pivot energy and to Ep = 12 TeV. The gray band corresponds to the 1σ error band of the fit. by HAWC is consistent with a low activity state over the whole 2141 days of observation. It is worth t… view at source ↗
Figure 3
Figure 3. M87 light curves for different time scales. The black point represent the calculated fluxes with a significance of ≥ 2σ; while the gray points represent the calculated fluxes with a significance of < 2σ. Top: daily LC. Middle: weekly LC. Bottom: monthly LC. −2 0 2 NGC 1275 Daily Integral flux −2 0 2 Weekly Integral flux 57000 57200 57400 57600 57800 58000 58200 58400 58600 58800 59000 59200 59400 59600 59800 MJD −2 … view at source ↗
Figures from the paper (4 more)
Figure 4
Figure 4. Figure 4: NGC 1275 light curves for different time scales. The black point represent the calculated fluxes with a significance of ≥ 2σ; while the gray points represent the calculated fluxes with a significance of < 2σ. Top: daily LC. Middle: weekly LC. Bottom: monthly LC [PITH_…
Figure 5
Figure 5. Figure 5: IC 310 light curves for different time scales. The black point represent the calculated fluxes with a significance of ≥ 2σ; while the gray points represent the calculated fluxes with a significance of < 2σ. Top: daily LC. Middle: weekly LC. Bottom: monthly LC. −5.0 −2.…
Figure 6
Figure 6. Figure 6: 3C 264 light curves for different time scales. The black point represent the calculated fluxes with a significance of ≥ 2σ; while the gray points represent the calculated fluxes with a significance of < 2σ. Top: daily LC. Middle: weekly LC. Bottom: monthly LC [PITH_FU…
Figure 7
Figure 7. Figure 7: Cumulative significance for the radio galaxies M87 (red crosses), NGC 1275 (blue circles) and 3C 264 (green triangles). For comparison, we also show the cumulative significance for the Crab Nebula (light-blue stars) and Markarian 421 (magenta squares). The behavior of …

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

64 extracted references · 28 canonical work pages

  1. [1]

    G., Ackermann, M., Adams, J., et al

    Aartsen, M. G., Ackermann, M., Adams, J., et al. 2020, PhRvL, 125, 121104, doi: 10.1103/PhysRevLett.125.121104

    doi:10.1103/physrevlett.125.121104 2020

  2. [2]

    U., Albert, A., Alfaro, R., et al

    Abeysekara, A. U., Albert, A., Alfaro, R., et al. 2017a, ApJ, 843, 40, doi: 10.3847/1538-4357/aa7556 —. 2017b, ApJ, 843, 39, doi: 10.3847/1538-4357/aa7555 —. 2017c, Science, 358, 911, doi: 10.1126/science.aan4880

    doi:10.3847/1538-4357/aa7556

  3. [3]

    U., et al

    Abeysekara, A. U., et al. 2017d, ApJ, 841, 100, doi: 10.3847/1538-4357/aa729e

    doi:10.3847/1538-4357/aa729e

  4. [4]

    U., Albert, A., Alfaro, R., et al

    Abeysekara, A. U., Albert, A., Alfaro, R., et al. 2019, ApJ, 881, 134, doi: 10.3847/1538-4357/ab2f7d —. 2023, Nuclear Instruments and Methods in Physics Research A, 1052, 168253, doi: 10.1016/j.nima.2023.168253 Radio Galaxies with HA WC 13

    work page arXiv 2019

  5. [5]

    A., Beilicke, M., Blaylock, G., et al

    Acciari, V. A., Beilicke, M., Blaylock, G., et al. 2008, ApJ, 679, 397, doi: 10.1086/587458

    doi:10.1086/587458 2008

  6. [6]

    A., Aliu, E., Arlen, T., et al

    Acciari, V. A., Aliu, E., Arlen, T., et al. 2009, Science, 325, 444, doi: 10.1126/science.1175406 —. 2010, ApJ, 716, 819, doi: 10.1088/0004-637X/716/1/819

    doi:10.1126/science.1175406 2009

  7. [7]

    2003, A&A, 403, L1, doi: 10.1051/0004-6361:20030372

    Aharonian, F., Akhperjanian, A., Beilicke, M., et al. 2003, A&A, 403, L1, doi: 10.1051/0004-6361:20030372

    work page doi:10.1051/0004-6361:20030372 2003

  8. [8]

    G., Bazer-Bachi, A

    Aharonian, F., Akhperjanian, A. G., Bazer-Bachi, A. R., et al. 2006, Science, 314, 1424, doi: 10.1126/science.1134408

    doi:10.1126/science.1134408 2006

Show all 64 references
  1. [9]

    L., Ansoldi, S., Antonelli, L

    Ahnen, M. L., Ansoldi, S., Antonelli, L. A., et al. 2017, A&A, 603, A25, doi: 10.1051/0004-6361/201630347

    2017 doi

  2. [10]

    L., Ansoldi, S., Antonelli, L., et al

    Ahnen, M. L., Ansoldi, S., Antonelli, L., et al. 2017, Astronomy & astrophysics, 603, A25

    2017

  3. [11]

    R., et al

    Albert, A., Alvarez, C., Angeles Camacho, J. R., et al. 2021, ApJ, 907, 67, doi: 10.3847/1538-4357/abca9a

    2021 doi

  4. [12]

    2024, ApJ, 972, 144, doi: 10.3847/1538-4357/ad5f2d

    Albert, A., Alfaro, R., Alvarez, C., et al. 2024, ApJ, 972, 144, doi: 10.3847/1538-4357/ad5f2d

    2024 doi

  5. [13]

    2008, ApJL, 685, L23, doi: 10.1086/592348 Aleksi´ c, J., Alvarez, E

    Albert, J., Aliu, E., Anderhub, H., et al. 2008, ApJL, 685, L23, doi: 10.1086/592348 Aleksi´ c, J., Alvarez, E. A., Antonelli, L. A., et al. 2012a, A&A, 539, L2, doi: 10.1051/0004-6361/201118668 —. 2012b, A&A, 544, A96, doi: 10.1051/0004-6361/201117827 Aleksi´ c, J., Antonelli...

    2008 doi

  6. [14]

    C., et al

    Alfaro, R., Alvarez, C., Arteaga-Vel´ azquez, J. C., et al. 2022, ApJ, 934, 158, doi: 10.3847/1538-4357/ac7b78

    2022 doi

  7. [15]

    2012, ApJ, 746, 141, doi: 10.1088/0004-637X/746/2/141

    Aliu, E., Arlen, T., Aune, T., et al. 2012, ApJ, 746, 141, doi: 10.1088/0004-637X/746/2/141

    2012 doi

  8. [16]

    N., Aharonian, F., et al

    Arcaro, C., Mathieu, d. N., Aharonian, F., et al. 2023, in Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Vol. 444, 696, doi: 10.22323/1.444.0696

    2023 doi

  9. [17]

    2020, ApJ, 896, 41, doi: 10.3847/1538-4357/ab910e Arteaga-Vel´ azquez, J

    Archer, A., Benbow, W., Bird, R., et al. 2020, ApJ, 896, 41, doi: 10.3847/1538-4357/ab910e Arteaga-Vel´ azquez, J. C. 2012a, in Journal of Physics Conference Series, Vol. 378, Journal of Physics Conference Series, 012005, doi: 10.1088/1742-6596/378/1/012005 Arteaga-Vel´ azquez...

    2020 doi

  10. [18]

    2017, ApJ, 848, 111, doi: 10.3847/1538-4357/aa8c7b

    Baghmanyan, V., Gasparyan, S., & Sahakyan, N. 2017, ApJ, 848, 111, doi: 10.3847/1538-4357/aa8c7b

    2017 doi

  11. [19]

    2019, PhD thesis, lmu

    Bangale, P. 2019, PhD thesis, lmu

    2019

  12. [20]

    2016, ApJ, 833, 279, doi: 10.3847/1538-4357/833/2/279

    Bednarek, W. 2016, ApJ, 833, 279, doi: 10.3847/1538-4357/833/2/279

    2016 doi

  13. [21]

    2012, in American Institute of Physics Conference Series, Vol

    Beilicke, M., & VERITAS Collaboration. 2012, in American Institute of Physics Conference Series, Vol. 1505, American Institute of Physics Conference Series, ed. F. A. Aharonian, W. Hofmann, & F. M. Rieger, 586–589, doi: 10.1063/1.4772328

    2012 doi

  14. [22]

    2019, in International Cosmic Ray Conference, Vol

    Benbow, W. 2019, in International Cosmic Ray Conference, Vol. 36, 36th International Cosmic Ray Conference (ICRC2019), 632, doi: 10.22323/1.358.0632

    2019 doi

  15. [23]

    V., da Costa, L

    Bernardi, M., Alonso, M. V., da Costa, L. N., et al. 2002, AJ, 123, 2990, doi: 10.1086/340463

    2002 doi

  16. [24]

    2022, ApJ, 938, 79, doi: 10.3847/1538-4357/ac8e64

    Boughelilba, M., Reimer, A., & Merten, L. 2022, ApJ, 938, 79, doi: 10.3847/1538-4357/ac8e64

    2022 doi

  17. [25]

    Brown, M. J. I., Moustakas, J., Smith, J. D. T., et al. 2014, ApJS, 212, 18, doi: 10.1088/0067-0049/212/2/18

    2014 doi

  18. [26]

    2024, ApJL, 975, L44, doi: 10.3847/2041-8213/ad8921 Cherenkov Telescope Array Consortium, T., :, Abe, K., et al

    Cao, Z., Aharonian, F., Axikegu, et al. 2024, ApJL, 975, L44, doi: 10.3847/2041-8213/ad8921 Cherenkov Telescope Array Consortium, T., :, Abe, K., et al. 2023, arXiv e-prints, arXiv:2309.03712, doi: 10.48550/arXiv.2309.03712 De Naurois, M. 2019, in 36th international cosmic ray...

    2024 doi arXiv

  19. [27]

    D., & Schlickeiser, R

    Dermer, C. D., & Schlickeiser, R. 1993, ApJ, 416, 458, doi: 10.1086/173251 Event Horizon Telescope Collaboration, Akiyama, K.,

    1993 doi

  20. [28]

    2019a, ApJL, 875, L1, doi: 10.3847/2041-8213/ab0ec7 —

    Alberdi, A., et al. 2019a, ApJL, 875, L1, doi: 10.3847/2041-8213/ab0ec7 —. 2019b, ApJL, 875, L2, doi: 10.3847/2041-8213/ab0c96 —. 2019c, ApJL, 875, L3, doi: 10.3847/2041-8213/ab0c57 —. 2019d, ApJL, 875, L4, doi: 10.3847/2041-8213/ab0e85 —. 2019e, ApJL, 875, L5, doi: 10.3847/20...

    doi

  21. [29]

    L., Ma, C., Arias, E

    Fey, A. L., Ma, C., Arias, E. F., et al. 2004, AJ, 127, 3587, doi: 10.1086/420998

    2004 doi

  22. [30]

    2014, MNRAS, 441, 1209, doi: 10.1093/mnras/stu652

    Fraija, N. 2014, MNRAS, 441, 1209, doi: 10.1093/mnras/stu652

    2014 doi

  23. [31]

    2016, ApJ, 830, 81, doi: 10.3847/0004-637X/830/2/81

    Fraija, N., & Marinelli, A. 2016, ApJ, 830, 81, doi: 10.3847/0004-637X/830/2/81

    2016 doi

  24. [32]

    2008, A&A, 487, 837, doi: 10.1051/0004-6361:200809691

    Franceschini, A., Rodighiero, G., & Vaccari, M. 2008, A&A, 487, 837, doi: 10.1051/0004-6361:200809691

    2008 doi

  25. [33]

    J., et al

    Weeren, R. J., et al. 2020, MNRAS, 499, 5791, doi: 10.1093/mnras/staa2003

    2020 doi

  26. [34]

    2012, MNRAS, 420, 2899, doi: 10.1111/j.1365-2966.2011.20044.x

    Giommi, P., Padovani, P., Polenta, G., et al. 2012, MNRAS, 420, 2899, doi: 10.1111/j.1365-2966.2011.20044.x

    2012

  27. [35]

    R., & Miley, G

    Gisler, G. R., & Miley, G. K. 1979, A&A, 76, 109

    1979

  28. [36]

    A., Brown, A

    Graham, J. A., Brown, A. M., & Chadwick, P. M. 2019, Monthly Notices of the Royal Astronomical Society, 485, 3277 14 H. E. S. S. Collaboration, Aharonian, F., Ait Benkhali, F., et al. 2023, A&A, 675, A138, doi: 10.1051/0004-6361/202346056

    2019 doi

  29. [37]

    2011, in International Cosmic Ray Conference, Vol

    Holder, J. 2011, in International Cosmic Ray Conference, Vol. 11, International Cosmic Ray Conference, 137, doi: 10.7529/ICRC2011/V12/H11

    2011 doi

  30. [38]

    2011, arXiv preprint arXiv:1111.1225

    Holder, J., Aliu, E., Arlen, T., et al. 2011, arXiv preprint arXiv:1111.1225

    2011 arXiv

  31. [39]

    2021, ApJ, 919, 110, doi: 10.3847/1538-4357/ac0ae4

    Imazawa, R., Fukazawa, Y., & Takahashi, H. 2021, ApJ, 919, 110, doi: 10.3847/1538-4357/ac0ae4

    2021 doi

  32. [40]

    U., Onah, C

    Iyida, E. U., Onah, C. I., Eya, I. O., & Odo, F. C. 2024, Ap&SS, 369, 106, doi: 10.1007/s10509-024-04371-x

    2024 doi

  33. [41]

    2012, A&A, 538, L1, doi: 10.1051/0004-6361/201118212

    Kadler, M., Eisenacher, D., Ros, E., et al. 2012, A&A, 538, L1, doi: 10.1051/0004-6361/201118212

    2012 doi

  34. [42]

    2018, ApJ, 864, 118, doi: 10.3847/1538-4357/aad6e3

    Kino, M., Wajima, K., Kawakatu, N., et al. 2018, ApJ, 864, 118, doi: 10.3847/1538-4357/aad6e3

    2018 doi

  35. [43]

    2021, ApJL, 920, L24, doi: 10.3847/2041-8213/ac24fa MAGIC Collaboration, Ansoldi, S., Antonelli, L

    Kino, M., Niinuma, K., Kawakatu, N., et al. 2021, ApJL, 920, L24, doi: 10.3847/2041-8213/ac24fa MAGIC Collaboration, Ansoldi, S., Antonelli, L. A., et al. 2018, A&A, 617, A91, doi: 10.1051/0004-6361/201832895

    2021 doi

  36. [44]

    2015, in Extragalactic Jets from Every Angle, ed

    Marinelli, A., & Fraija, N. 2015, in Extragalactic Jets from Every Angle, ed. F. Massaro, C. C. Cheung, E. Lopez, & A. Siemiginowska, Vol. 313, 169–174, doi: 10.1017/S1743921315002136

    2015 doi

  37. [45]

    2010, The Astronomer’s Telegram, 2510, 1

    Mariotti, M. 2010, The Astronomer’s Telegram, 2510, 1

    2010

  38. [46]

    P., Cˆ ot´ e, P., et al

    Mei, S., Blakeslee, J. P., Cˆ ot´ e, P., et al. 2007, ApJ, 655, 144, doi: 10.1086/509598

    2007 doi

  39. [47]

    T., Georganopoulos, M., Sparks, W

    Meyer, E. T., Georganopoulos, M., Sparks, W. B., et al. 2015, Nature, 521, 495, doi: 10.1038/nature14481

    2015 doi

  40. [48]

    2016, The Astronomer’s Telegram, 9689, 1 —

    Mirzoyan, R. 2016, The Astronomer’s Telegram, 9689, 1 —. 2017, The Astronomer’s Telegram, 9929, 1 Molero Gonzalez, M., Fortson, L., Nievas, M., et al. 2023, in Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Vol. 444, 572, doi: 10.22323/1.444.0572

    2016 doi

  41. [49]

    2018, The Astronomer’s Telegram, 11436, 1

    Mukherjee, R. 2018, The Astronomer’s Telegram, 11436, 1

    2018

  42. [50]

    2010, A&A, 519, L6, doi: 10.1051/0004-6361/201014499

    Neronov, A., Semikoz, D., & Vovk, I. 2010, A&A, 519, L6, doi: 10.1051/0004-6361/201014499

    2010 doi

  43. [51]

    N., & Lobanov, A

    Pashchenko, I. N., & Lobanov, A. P. 2023, MNRAS, 526, 5949, doi: 10.1093/mnras/stad3061

    2023 doi

  44. [52]

    S., Padgett, C

    Perlman, E. S., Padgett, C. A., Georganopoulos, M., et al. 2010, ApJ, 708, 171, doi: 10.1088/0004-637X/708/1/171

    2010 doi

  45. [53]

    2014, A&A, 562, A12, doi: 10.1051/0004-6361/201322833

    Mastichiadis, A. 2014, A&A, 562, A12, doi: 10.1051/0004-6361/201322833

    2014 doi

  46. [54]

    2018, Galaxies, 6, 116, doi: 10.3390/galaxies6040116

    Rieger, F., & Levinson, A. 2018, Galaxies, 6, 116, doi: 10.3390/galaxies6040116

    2018 doi

  47. [55]

    2022, Galaxies, 10, 61, doi: 10.3390/galaxies10030061

    Rulten, C. 2022, Galaxies, 10, 61, doi: 10.3390/galaxies10030061

    2022 doi

  48. [56]

    2012, PhRvD, 85, 043012, doi: 10.1103/PhysRevD.85.043012

    Sahu, S., Zhang, B., & Fraija, N. 2012, PhRvD, 85, 043012, doi: 10.1103/PhysRevD.85.043012

    2012 doi

  49. [57]

    1998, Astronomy and Astrophysics, v

    Sijbring, D., & de Bruyn, A. 1998, Astronomy and Astrophysics, v. 331, p. 901-915 (1998), 331, 901

    1998

  50. [58]

    Sijbring, D., & de Bruyn, A. G. 1998, A&A, 331, 901

    1998

  51. [59]

    F., & Rood, H

    Struble, M. F., & Rood, H. J. 1999, ApJS, 125, 35, doi: 10.1086/313274

    1999 doi

  52. [60]

    E., & Darling, J

    Truebenbach, A. E., & Darling, J. 2017, ApJS, 233, 3, doi: 10.3847/1538-4365/aa9026

    2017 doi

  53. [61]

    M., & Padovani, P

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

    1995 doi

  54. [62]

    J., Edge, A

    Wilman, R. J., Edge, A. C., & Johnstone, R. M. 2005, MNRAS, 359, 755, doi: 10.1111/j.1365-2966.2005.08956.x

    2005

  55. [63]

    2024, The Astronomer’s Telegram, 16513, 1

    Xiang, G., Zha, M., Yao, Z., Zhou, J., & Xing, Y. 2024, The Astronomer’s Telegram, 16513, 1

    2024

  56. [64]

    H., Anderson, J

    Xu, M. H., Anderson, J. M., Heinkelmann, R., et al. 2019, ApJS, 242, 5, doi: 10.3847/1538-4365/ab16ea

    2019 doi

Pith tools

Reviewed August 6, 2026 · model on record in the stance chip above.