Pith. sign in

REVIEW 3 major objections 3 minor 57 references

Serendipitous VERITAS upper limits on the low-luminosity AGN NGC 4278 place its very-high-energy gamma-ray peak between 100 GeV and 2 TeV and make a coronal proton model a viable explanation.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

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

T0 review · deepseek-v4-flash

2026-08-04 05:46 UTC pith:BZ2B3GIA

load-bearing objection Solid VERITAS upper limits on NGC 4278, but the headline index constraint rests on an unverified sampling assumption and the corona model is explicitly illustrative—worth a careful referee, not a desk reject. the 3 major comments →

arxiv 2603.17511 v1 pith:BZ2B3GIA submitted 2026-03-18 astro-ph.HE

VERITAS Observations Contemporaneous with the LHAASO Detection of NGC 4278

The VERITAS Collaboration: A. Archer , P. Bangale , J. T. Bartkoske , W. Benbow , J. H. Buckley , Y. Chen , J. L. Christiansen , A. J. Chromey
show 60 more authors
A. Duerr M. Errando M. Escobar Godoy S. Feldman Q. Feng S. Filbert L. Fortson A. Furniss W. Hanlon O. Hervet C. E. Hinrichs J. Holder Z. Hughes T. B. Humensky M. Iskakova W. Jin M. N. Johnson M. Kertzman M. Kherlakian D. Kieda T. K. Kleiner N. Korzoun S. Kumar S. Kundu M. J. Lang M. Lundy G. Maier C. McSorley P. Moriarty R. Mukherjee W. Ning S. O'Brien M. Ohishi M. A. Ong A. Pandey C. Poggemann M. Pohl E. Pueschel J. Quinn P. L. Rabinowitz K. Ragan P. T. Reynolds D. Ribeiro L. Rizk E. Roache I. Sadeh L. Saha H. Salzmann M. Santander G. H. Sembroski R. Shang M. Splettstoesser D. Tak A. K. Talluri I. Thoreson J. V. Tucci J. Valverde D. A. Williams S. L. Wong T. Yoshikoshi
This is my paper
classification astro-ph.HE
keywords gamma-ray astronomylow-luminosity active galactic nucleiNGC 4278very-high-energy gamma raysflux upper limitshadronic corona modelspectral energy distributionneutrino predictions
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper argues that the nearby low-luminosity active galactic nucleus NGC 4278, recently detected in TeV gamma rays by LHAASO, has its gamma-ray peak at a few hundred GeV rather than in the 1–20 TeV band. Using serendipitous VERITAS observations that overlap the LHAASO campaign, the authors derive a 95% confidence upper limit on the quasi-quiet flux that, combined with Fermi-LAT upper limits, constrains the power-law index to below 3.13 and locates the SED peak anywhere between 100 GeV and 2 TeV. They then show that a hadronic corona model, in which protons accelerated in the AGN corona interact with X-ray photons to produce pions, can naturally explain both the hard X-rays and the TeV gamma rays without violating energetics. If correct, this identifies a new mechanism for transient TeV emission from low-luminosity AGN and predicts a neutrino signal slightly below IceCube's current sensitivity.

Core claim

The central claim is that the quasi-quiet very-high-energy spectrum of NGC 4278 is harder than a simple extrapolation of LHAASO's power law allows, with the spectral index constrained to Gamma < 3.13 at 95% confidence, and that the peak of the gamma-ray spectral energy distribution lies between 100 GeV and 2 TeV. The paper further claims that this peak can be produced by photohadronic interactions of ~20 TeV protons with ~10 keV X-ray photons in the AGN corona, without the need for relativistic jet boosting, and that the secondary electrons from pion decay naturally produce the observed hard X-ray component.

What carries the argument

The argument rests on two pieces. First, the VERITAS flux upper limit of 8.3e-9 TeV^-1 m^-2 s^-1 at 680 GeV in the quasi-quiet state, obtained from 6.53 hours of serendipitous observations, which is used in a log-parabolic fit to the LHAASO and Fermi-LAT data to bracket the SED peak. Second, the analytic corona model: protons accelerated to ~20 TeV interact with ~10 keV synchrotron X-ray photons through the Delta resonance, producing pions that decay into gamma rays, neutrinos, and electron-positron pairs; the pairs cool by synchrotron emission and re-inject hard X-rays, providing a self-amplifying target photon field.

Load-bearing premise

The 6.53 hours of VERITAS exposure spread over roughly a year are assumed to represent the average flux of the entire quasi-quiet state, so that the upper limit can be combined with the time-averaged LHAASO spectrum to constrain the spectral index.

What would settle it

A longer, deeper observation with an imaging Cherenkov telescope that detects NGC 4278 in the quasi-quiet state at a flux above the reported upper limit would falsify the index constraint; alternatively, if a future SED fit places the gamma-ray peak outside 100 GeV–2 TeV, or if a stacked search of similar low-luminosity AGN finds no neutrino signal matching the hadronic prediction, the coronal p-gamma interpretation would need revision.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • The VHE gamma-ray peak of NGC 4278 lies in a band where both VERITAS and future Cherenkov telescopes are sensitive, so a firm detection or deeper upper limit can directly test the predicted index constraint.
  • The hadronic corona model predicts a neutrino spectrum that, though below IceCube's steady sensitivity, could be probed with stacked low-luminosity AGN samples or future neutrino telescopes.
  • If the peak is genuinely at a few hundred GeV, LHAASO's detection in the 1–20 TeV band requires a relatively hard tail, implying a specific high-energy cutoff in the proton spectrum.
  • The model provides a self-consistent explanation for the historically puzzling hard X-ray spectrum of NGC 4278 as synchrotron radiation from secondary pairs rather than intrinsic jet emission.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same coronal p-gamma mechanism might apply to other low-luminosity AGN with hard X-ray peaks, making the class a population of faint, transient TeV emitters worth targeting in future surveys.
  • If the quasi-quiet state is not actually steady at the level probed by the 6.53 hours of VERITAS exposure, the index constraint and peak location could shift; a dedicated monitoring campaign could test this.
  • The paper's assumption that the two LHAASO quasi-quiet points share the active-state curvature is fragile; a future observation with more quasi-quiet flux points could confirm or alter the peak bracket.
  • The model's implication that the neutrino flux at ~100 TeV is comparable to that of NGC 1068 suggests that high-energy neutrino telescopes might distinguish hadronic corona models from leptonic jet models by looking for a spectral crossover.

Editorial analysis

A structured set of objections, weighed in public.

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

Referee Report

3 major / 3 minor

Summary. This paper reports VERITAS observations of the LLAGN NGC 4278 that are contemporaneous with the LHAASO detection of 1LHAASO J1219+2915. NGC 4278 is not detected; 95% CL flux upper limits are derived for active and quasi-quiet states (Table 1). Combining the quasi-quiet VERITAS upper limit with LHAASO and Fermi-LAT data, the authors infer that the power-law index of the quasi-quiet VHE spectrum must be Gamma < 3.13 (if VERITAS samples the state average), and that the SED peak lies between 100 GeV and 2 TeV. They then present an illustrative hadronic corona model with p-gamma interactions that can simultaneously produce hard X-rays and TeV gamma rays, with neutrinos slightly below IceCube sensitivity.

Significance. The observational core is standard and reliable: the analysis uses reflected-region background estimation, Li&Ma significances, and is cross-checked with an independent analysis package. The upper limits at ~280 GeV are more constraining than Fermi-LAT for this source and are a useful new data point. The authors are careful to label their corona model as illustrative and to state the main assumptions. If the temporal averaging assumption is justified, the Gamma < 3.13 constraint and the SED peak bracket would be the first meaningful VHE spectral constraints for a quasi-quiet LLAGN and would favor models in which the VHE component peaks below the LHAASO band.

major comments (3)
  1. [§5 (Spectral Energy Distribution)] Section 5 states 'Under the assumption that the VERITAS observations probe the average flux during this state, the power-law index cannot exceed 3.13...' This assumption is load-bearing: the VERITAS quasi-quiet exposure (6.53 h over MJD 59280–59697) covers only the pre-active part and ~3.5 months after the active window, while the LHAASO quasi-quiet state spans MJD 59278–60248. The source shows factor ~4 active/quiet contrast, so unresolved variability within the quiet state could make the VERITAS sample unrepresentative of the time-averaged LHAASO spectrum. The constraint may be artificially strong if the state-average flux is higher. Please either justify representativeness with LHAASO light-curve data restricted to the VERITAS windows or explicitly downgrade the claim to a time-averaged upper limit that is not directly comparable to the LHAASO state average.
  2. [§5 log-parabolic fit] The log-parabolic fit treats the VERITAS upper limit by 'assuming that it represents a flux of zero, with an uncertainty that is half of the flux upper limit.' This ad hoc replacement can bias the fitted curvature and hence the reported 100 GeV–2 TeV peak range. It is also unclear whether the active-period VERITAS limit (Table 1, 1e-7) or quasi-quiet limit (8.3e-9) was used. A proper likelihood (e.g., including the upper limit as a censored data point) and a sensitivity test should be reported before the peak bracket is used in the conclusions.
  3. [§5, Table 2] The text says Fermi-LAT 'provides spectral fluxes even when they are of low significance, and these were included in the fit,' yet Table 2 reports only 95% upper limits. If low-significance flux points are used as measurements, the fit may be biased; if only upper limits are used, the procedure should be stated. Please clarify and, if fluxes are used, report their values and significances.
minor comments (3)
  1. [Abstract] The abstract's statement that 'The flux upper limits constrain the photon spectrum of the quasi-quiet period' omits the temporal-representativeness caveat made explicit in §5. The abstract should carry the same conditionality as the body text.
  2. [§6.1] Typo: 'should not not be limited by the infall time' should be 'should not be limited by the infall time.' Also 'implicitely' should be 'implicitly.'
  3. [Figure 1] Consider adding a scale bar or a clear angular-size annotation; the point spread function is shown, but the source separation from the 3.1σ fluctuation at 0.15° is easier to judge with an explicit angular scale.

Circularity Check

0 steps flagged

No significant circularity: the core results are independent data products and the corona model is explicitly illustrative, not a fitted prediction.

full rationale

The paper's main quantitative results are independent of its interpretive model. The VERITAS upper limit is a null-detection measurement; the Γ<3.13 statement is conditional on an explicitly stated empirical assumption about flux representativeness ('Under the assumption that the VERITAS observations probe the average flux during this state'), not on a parameter fitted from LHAASO. The log-parabolic SED fit is a least-squares fit to independent Fermi-LAT and LHAASO data, with the VERITAS upper limit folded in as a pseudo-measurement; this is statistically crude but not circular. The corona interpretation is self-labeled as an example rather than a prediction: 'We emphasize that both the gamma-ray spectrum and the input X-ray and particle spectra used to compute it really are examples and not a model prediction.' The model uses observed X-rays as input and checks consistency (e.g., secondary-electron synchrotron comparable to hard X-rays), rather than deriving the data from itself. Self-citations in the paper concern VERITAS instrument calibration, reconstruction, and analysis cross-checks; none is load-bearing or invoked to forbid alternatives. No fitted parameter is renamed as a prediction, and no uniqueness theorem is imported from the authors.

Axiom & Free-Parameter Ledger

7 free parameters · 8 axioms · 0 invented entities

The central empirical claim (non-detection and upper limits) rests on instrument calibrations and the LHAASO source association, not on the model. The interpretive rather than predictive character of the model is reflected in the seven hand-set quantities (proton spectrum, radius, magnetic field, neutrino normalization, X-ray target shape, distance, SED-fit parameters): all are either chosen to match the observed SED or taken from the same data the model explains. This is a consistency check of a scenario, not a derivation. No new particles, forces, or conserved quantities are postulated; the model's agents (coronal protons, pions, secondary leptons, photons, neutrinos) are standard physics.

free parameters (7)
  • Proton injection spectrum (normalization, index, break energy) = N_p proportional to E^-2.2 (1 + E/15 TeV)^2 (Eq. 5); normalization set to match observed gamma-ray flux
    Hand-chosen 'example' spectrum, explicitly not a model prediction (Section 6.1); the shape determines the gamma-ray and neutrino spectral output.
  • Emission-region radius R_15 = R / 10^15 cm = R = 10^15 cm (R_15 = 1)
    Assumed one-zone spherical source, about 12 R_G for M_BH ~ 3x10^8 M_sun; enters photon density (Eq. 3), opacity, escape time (Eq. 8), and magnetic field (Eq. 9).
  • Magnetic field B = greater than about 4 G (for R_15 = 1) via Eq. 9; 30 mG in the SSC-consistent variant
    Lower bound from equating magnetic energy influx to the nonthermal luminosity; the exact value used in efficiency estimates is model-dependent.
  • Neutrino spectrum normalization at 1 TeV = 2x10^-12 TeV^-1 cm^-2 s^-1 (active); 3x10^-13 (quasi-quiet)
    Assumed to mirror the measured gamma-ray flux (Section 6.1); directly determines the quoted IceCube event counts.
  • Log-parabolic SED parameters F_0, Gamma, b = F_0 = (7.6 +/- 1.3) x 10^-10 ph TeV^-1 cm^-2 s^-1; Gamma = 2.66 +/- 0.21; b = 0.125 +/- 0.048 (95% CI)
    Least-squares fit to LHAASO and Fermi-LAT data with the VERITAS upper limit approximated as zero flux (Section 5); drives the 100 GeV - 2 TeV peak bracket.
  • X-ray target photon spectrum shape (index -1.8, cutoff 150 keV) = N_X proportional to E^-1.8 exp(-E/150 keV) (Eq. 4)
    Assumed to be typical of corona spectra and consistent with that observed during the LHAASO high state (Section 6.1); the normalization is taken from the observed Swift-XRT luminosity.
  • Luminosity distance to NGC 4278 = about 13 Mpc (CMB-frame / redshift-independent estimates)
    The authors adopt 13 Mpc rather than the nominal about 10 Mpc from z ~ 0.002; scales L_X (Eq. 2) and every luminosity-derived quantity; uncertainty is noted in Section 6.1.
axioms (8)
  • standard math Delta-resonance p-gamma kinematics: proton energy about 20 TeV for target photons about 10 keV (Eq. 1)
    Standard photohadronic physics (Gaisser et al. 1995; Hummer et al. 2010); converts the gamma-ray peak to proton energy and sets the target photon band.
  • domain assumption Optically thin emission zone; pair-production opacity below unity for R_15 greater than about 0.01
    Section 6.1; required so the observed gamma-ray peak is intrinsic and the neutrino flux mirrors the gamma-ray flux.
  • standard math Inelasticity K = 0.2 and sigma_p-gamma about 5x10^-28 cm^2 for the energy-loss time (Eq. 6)
    Taken from Muecke et al. 2000; feeds the t_p-gamma and efficiency estimates.
  • domain assumption Bohm diffusion in a fully turbulent B about 4 G field bounds the escape time (Eq. 8)
    Section 6.1; needed for the 'up to a few tens of percent' radiative efficiency and the conclusion that the model avoids an energetics problem.
  • domain assumption Magnetic energy influx at least the observed nonthermal luminosity (Eq. 9) and a magnetically supported corona
    Section 6.2; rests on radiative-MHD simulations (Jiang et al. 2014); sets B and the implied proton injection power of 10^43 erg/s.
  • domain assumption Most optical emission originates outside the gamma-ray emission zone
    Section 6.1; argued from the optical SED peaking and host-galaxy attribution (Wang et al. 2024); otherwise optical photons would absorb the TeV emission.
  • domain assumption 1LHAASO J1219+2915 is correctly associated with NGC 4278 and the active/quasi-quiet split (MJD 59449-59589) is correct
    Section 2; taken from Z. Cao et al. 2024a,b. The VERITAS pointing, the Fermi-LAT model, and the SED interpretation all presuppose this association in a field containing three known blazars within 2 degrees.
  • domain assumption Quasi-quiet VERITAS exposure samples the average quiet-state flux
    Section 5, explicitly stated; without it the Gamma < 3.13 index bound does not follow from the upper limit.

pith-pipeline@v1.3.0-alltime-deepseek · 15420 in / 23826 out tokens · 209128 ms · 2026-08-04T05:46:53.302925+00:00 · methodology

0 comments
read the original abstract

Significant gamma-ray emission between 1 TeV and 20 TeV from a point source, 1LHAASO J1219+2915, consistent with the location of the LINER/LLAGN galaxy NGC 4278 was recently reported by the LHAASO collaboration. These data were later split into active and quasi-quiet states, with most of the LHAASO significance coming from the active state (MJD 59449-59589). Subsequent analysis of Fermi-LAT and Swift-XRT observations have been used to explore the double-peaked broad-band emission. Models of the spectral energy distribution (SED) are currently unconstrained due to the lack of contemporaneous multi-wavelength data at either peak. Here we report serendipitous observations of NGC 4278 with VERITAS, made possible by the contemporaneous observations of the nearby blazars 1ES 1218+304, 1ES 1215+303, and W Comae, each of which are located within $2^\circ$ of NGC 4278. VERITAS did not detect any gamma-ray emission and a flux upper limit was calculated. The flux upper limits constrain the photon spectrum of the quasi-quiet period, and together with Fermi-LAT, indicate a peak in the SED between 100 GeV and 2 TeV. We present an interpretation of the broadband SED that is based on acceleration of protons in the corona of the AGN, followed by p-$\gamma$ interactions and optically thin $\gamma$-ray emission. Within this framework, the implied neutrino signal is slightly below the current sensitivity of IceCube.

Figures

Figures reproduced from arXiv: 2603.17511 by A. Duerr, A. Furniss, A. J. Chromey, A. K. Talluri, A. Pandey, C. E. Hinrichs, C. McSorley, C. Poggemann, D. A. Williams, D. Kieda, D. Ribeiro, D. Tak, E. Pueschel, E. Roache, G. H. Sembroski, G. Maier, H. Salzmann, I. Sadeh, I. Thoreson, J. H. Buckley, J. Holder, J. L. Christiansen, J. Quinn, J. T. Bartkoske, J. Valverde, J. V. Tucci, K. Ragan, L. Fortson, L. Rizk, L. Saha, M. A. Ong, M. Errando, M. Escobar Godoy, M. Iskakova, M. J. Lang, M. Kertzman, M. Kherlakian, M. Lundy, M. N. Johnson, M. Ohishi, M. Pohl, M. Santander, M. Splettstoesser, N. Korzoun, O. Hervet, P. Bangale, P. L. Rabinowitz, P. Moriarty, P. T. Reynolds, Q. Feng, R. Mukherjee, R. Shang, S. Feldman, S. Filbert, S. Kumar, S. Kundu, S. L. Wong, S. O'Brien, T. B. Humensky, The VERITAS Collaboration: A. Archer, T. K. Kleiner, T. Yoshikoshi, W. Benbow, W. Hanlon, W. Jin, W. Ning, Y. Chen, Z. Hughes.

Figure 1
Figure 1. Figure 1: VERITAS sky map from observations of 1ES 1218+304, 1ES 1215+303, and W Comae contemporaneous with the LHAASO analysis. The location of each source, including NGC 4278 is marked on the map with a ‘+’ sym￾bol and the point spread function is shown in the bottom right. There is no evidence for the detection of NGC 4278 in the VERITAS sky map. A background fluctuation with a pre-trials significance of 3.1σ can… view at source ↗
Figure 2
Figure 2. Figure 2: NGC 4278 SED during the active and quasi-quiet periods: LHAASO-WCDA fluxes and upper limits from LHAA￾SO-KM2A (blue & purple), VERITAS (yellow & orange), and Fermi-LAT (green & light green). The E. Bronzini et al. (2024) Fermi-LAT (gray) is from data spanning the 1LHAASO Catalog dates. The power-law fit to the LHAASO data is from Z. Cao et al. (2024b). A log-parabolic model was fit to the combined dataset … view at source ↗

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

57 extracted references · 11 canonical work pages · 2 internal anchors

  1. [1]

    2020, ApJS, 247, 33, doi: 10.3847/1538-4365/ab6bcb

    Abdollahi, S., Acero, F., Ackermann, M., et al. 2020, ApJS, 247, 33, doi: 10.3847/1538-4365/ab6bcb

    doi:10.3847/1538-4365/ab6bcb 2020

  2. [2]

    A., Aliu, E., Beilicke, M., et al

    Acciari, V. A., Aliu, E., Beilicke, M., et al. 2008, ApJL, 684, L73, doi: 10.1086/592244

    work page doi:10.1086/592244 2008

  3. [3]

    B., Archer, A., et al

    Acharyya, A., Adams, C. B., Archer, A., et al. 2023, ApJ, 954, 70, doi: 10.3847/1538-4357/ace327

    doi:10.3847/1538-4357/ace327 2023

  4. [4]

    B., Benbow, W., Brill, A., et al

    Adams, C. B., Benbow, W., Brill, A., et al. 2022, A&A, 658, A83, doi: 10.1051/0004-6361/202142275

    doi:10.1051/0004-6361/202142275 2022

  5. [5]

    2019, arXiv e-prints, arXiv:1902.08429, doi: 10.48550/arXiv.1902.08429

    Albert, A., Alfaro, R., Ashkar, H., et al. 2019, arXiv e-prints, arXiv:1902.08429, doi: 10.48550/arXiv.1902.08429

    Pith/arXiv arXiv doi:10.48550/arxiv.1902.08429 2019

  6. [6]

    2013, arXiv e-prints, arXiv:1303.3514, doi: 10.48550/arXiv.1303.3514

    Atwood, W., Albert, A., Baldini, L., et al. 2013, arXiv e-prints, arXiv:1303.3514, doi: 10.48550/arXiv.1303.3514

    Pith/arXiv arXiv doi:10.48550/arxiv.1303.3514 2013

  7. [7]

    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, doi: 10.48550/arXiv.2307.12546

    Pith/arXiv arXiv doi:10.48550/arxiv.2307.12546 2023

  8. [8]

    H., Digel, S

    Ballet, J., Burnett, T. H., Digel, S. W., & Lott, B. 2020, arXiv e-prints, arXiv:2005.11208, doi: 10.48550/arXiv.2005.11208

    Pith/arXiv arXiv doi:10.48550/arxiv.2005.11208 2020

  9. [9]

    2007, A&A, 466, 1219, doi: 10.1051/0004-6361:20066674

    Berge, D., Funk, S., & Hinton, J. 2007, A&A, 466, 1219, doi: 10.1051/0004-6361:20066674

    doi:10.1051/0004-6361:20066674 2007

  10. [10]

    Blaufuss, E., Kintscher, T., Lu, L., & Tung, C. F. 2019,

    2019

  11. [11]

    PoS, ICRC2019, 1021, doi: 10.22323/1.358.1021

    work page doi:10.22323/1.358.1021

  12. [12]

    2024, private communication

    Bronzini, E. 2024, private communication

    2024

  13. [13]

    Fermi-LAT detection of the low-luminosity radio galaxy NGC 4278 during the LHAASO campaign

    Bronzini, E., Grandi, P., Torresi, E., & Buson, S. 2024, arXiv e-prints, arXiv:2409.17255, doi: 10.48550/arXiv.2409.17255

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2409.17255 2024

  14. [14]

    2019, A&A, 627, A13, doi: 10.1051/0004-6361/201834143

    Bulgarelli, A., Fioretti, V., Parmiggiani, N., et al. 2019, A&A, 627, A13, doi: 10.1051/0004-6361/201834143

    work page doi:10.1051/0004-6361/201834143 2019

  15. [15]

    2024a, ApJS, 271, 25, doi: 10.3847/1538-4365/acfd29

    Cao, Z., Aharonian, F., An, Q., et al. 2024a, ApJS, 271, 25, doi: 10.3847/1538-4365/acfd29

    doi:10.3847/1538-4365/acfd29

  16. [16]

    2024b, ApJL, 971, L45, doi: 10.3847/2041-8213/ad5e6d

    Cao, Z., Aharonian, F., Axikegu, et al. 2024b, ApJL, 971, L45, doi: 10.3847/2041-8213/ad5e6d

    doi:10.3847/2041-8213/ad5e6d 2041

  17. [17]

    T., et al

    Chen, S., Das, A., Zhang, B. T., et al. 2026, Physical origin of very-high-energy gamma rays from the low-luminosity active galactic nucleus NGC 4278 and implications for neutrino observations, https://arxiv.org/abs/2601.23242 Cherenkov Telescope Array Consortium, Acharya, B. S.,

    arXiv 2026

  18. [18]

    2019, Science with the Cherenkov Telescope Array, doi: 10.1142/10986

    Agudo, I., et al. 2019, Science with the Cherenkov Telescope Array, doi: 10.1142/10986

    doi:10.1142/10986 2019

  19. [19]

    2017, in International Cosmic Ray

    Christiansen, J. 2017, in International Cosmic Ray

    2017

  20. [20]

    301, 35th International Cosmic Ray Conference (ICRC2017), 789, doi: 10.22323/1.301.0789

    Conference, Vol. 301, 35th International Cosmic Ray Conference (ICRC2017), 789, doi: 10.22323/1.301.0789

    work page doi:10.22323/1.301.0789

  21. [21]

    2008, in International Cosmic Ray Conference, Vol

    Cogan, P. 2008, in International Cosmic Ray Conference, Vol. 3, International Cosmic Ray Conference, 1385–1388, doi: 10.48550/arXiv.0709.4233

    Pith/arXiv arXiv doi:10.48550/arxiv.0709.4233 2008

  22. [22]

    2019, The Astrophysical Journal, 886, 122, doi: 10.3847/1538-4357/ab4c33 de Vaucouleurs, G., de Vaucouleurs, A., Corwin, Jr., H

    Comisso, L., & Sironi, L. 2019, The Astrophysical Journal, 886, 122, doi: 10.3847/1538-4357/ab4c33 de Vaucouleurs, G., de Vaucouleurs, A., Corwin, Jr., H. G., et al. 1991, Third Reference Catalogue of Bright Galaxies

    doi:10.3847/1538-4357/ab4c33 2019

  23. [23]

    2024, ApJ, 974, 56, doi: 10.3847/1538-4357/ad6d65

    Dutta, S., & Gupta, N. 2024, ApJ, 974, 56, doi: 10.3847/1538-4357/ad6d65

    work page doi:10.3847/1538-4357/ad6d65 2024

  24. [24]

    Relativistic Jets in Radio-Weak Quasars and LINER Galaxies

    Falcke, H., Wilson, A. S., & Ho, L. C. 1997, in Relativistic Jets in AGNs, ed. M. Ostrowski, M. Sikora, G. Madejski, & M. Begelman, 13–19, doi: 10.48550/arXiv.astro-ph/9708126 11

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.astro-ph/9708126 1997

  25. [25]

    Fiorillo, D. F. G., Comisso, L., Peretti, E., Petropoulou, M., & Sironi, L. 2024a, ApJ, 974, 75, doi: 10.3847/1538-4357/ad7021

    doi:10.3847/1538-4357/ad7021

  26. [26]

    Fiorillo, D. F. G., Petropoulou, M., Comisso, L., Peretti, E., & Sironi, L. 2024b, ApJL, 961, L14, doi: 10.3847/2041-8213/ad192b

    doi:10.3847/2041-8213/ad192b 2041

  27. [27]

    P., Lamb, R

    Fomin, V. P., Lamb, R. C., Lewis, D. A., & Punch, M. 1991, in International Cosmic Ray Conference, Vol. 1, International Cosmic Ray Conference, 468

    1991

  28. [28]

    K., Halzen, F., & Stanev, T

    Gaisser, T. K., Halzen, F., & Stanev, T. 1995, PhR, 258, 173, doi: 10.1016/0370-1573(95)00003-Y

    work page doi:10.1016/0370-1573(95)00003-y 1995

  29. [29]

    2019, Nature Astronomy, 3, 88, doi: 10.1038/s41550-018-0610-1

    Gao, S., Fedynitch, A., Winter, W., & Pohl, M. 2019, Nature Astronomy, 3, 88, doi: 10.1038/s41550-018-0610-1

    doi:10.1038/s41550-018-0610-1 2019

  30. [30]

    2017, The Astrophysical Journal, 843, 109, doi: 10.3847/1538-4357/aa7754

    Gao, S., Pohl, M., & Winter, W. 2017, The Astrophysical Journal, 843, 109, doi: 10.3847/1538-4357/aa7754

    doi:10.3847/1538-4357/aa7754 2017

  31. [31]

    B., & Giovannini, G

    Giroletti, M., Taylor, G. B., & Giovannini, G. 2005, ApJ, 622, 178, doi: 10.1086/427898

    doi:10.1086/427898 2005

  32. [32]

    C., Bertsch, D

    Hartman, R. C., Bertsch, D. L., Bloom, S. D., et al. 1999, ApJS, 123, 79, doi: 10.1086/313231

    doi:10.1086/313231 1999

  33. [33]

    Heckman, T. M. 1980, A&A, 87, 152

    1980

  34. [34]

    W., Badran, H

    Holder, J., Atkins, R. W., Badran, H. M., et al. 2006, Astroparticle Physics, 25, 391, doi: 10.1016/j.astropartphys.2006.04.002 H¨ ummer, S., R¨ uger, M., Spanier, F., & Winter, W. 2010, ApJ, 721, 630, doi: 10.1088/0004-637X/721/1/630 IceCube Collaboration, Abbasi, R., Ackermann, M., et al. 2022, Science, 378, 538, doi: 10.1126/science.abg3395

    doi:10.1016/j.astropartphys.2006.04.002 2006

  35. [35]

    2024, PASJ, 76, 996, doi: 10.1093/pasj/psae065

    Inoue, Y., Takasao, S., & Khangulyan, D. 2024, PASJ, 76, 996, doi: 10.1093/pasj/psae065

    doi:10.1093/pasj/psae065 2024

  36. [36]

    M., & Davis, S

    Jiang, Y.-F., Stone, J. M., & Davis, S. W. 2014, ApJ, 784, 169, doi: 10.1088/0004-637X/784/2/169

    doi:10.1088/0004-637x/784/2/169 2014

  37. [37]

    2012, MNRAS, 420, 1825, doi: 10.1111/j.1365-2966.2011.19805.x

    Jin, C., Ward, M., Done, C., & Gelbord, J. 2012, MNRAS, 420, 1825, doi: 10.1111/j.1365-2966.2011.19805.x

    arXiv 2012

  38. [38]

    B., Quataert, E., et al

    Kempski, P., Fielding, D. B., Quataert, E., et al. 2023, MNRAS, 525, 4985, doi: 10.1093/mnras/stad2609

    doi:10.1093/mnras/stad2609 2023

  39. [39]

    L., Readhead, A

    Kiehlmann, S., Lister, M. L., Readhead, A. C. S., et al. 2024, ApJ, 961, 240, doi: 10.3847/1538-4357/ad0c56

    doi:10.3847/1538-4357/ad0c56 2024

  40. [40]

    2021, PhRvD, 104, 063020, doi: 10.1103/PhysRevD.104.063020

    Lemoine, M. 2021, PhRvD, 104, 063020, doi: 10.1103/PhysRevD.104.063020

    doi:10.1103/physrevd.104.063020 2021

  41. [41]

    2023, Journal of Plasma Physics, 89, 175890501, doi: 10.1017/S0022377823000946

    Lemoine, M. 2023, Journal of Plasma Physics, 89, 175890501, doi: 10.1017/S0022377823000946

    doi:10.1017/s0022377823000946 2023

  42. [42]

    2025, PhRvE, 112, 015205, doi: 10.1103/3xxg-x5dg

    Lemoine, M. 2025, PhRvE, 112, 015205, doi: 10.1103/3xxg-x5dg

    doi:10.1103/3xxg-x5dg 2025

  43. [43]

    2025, A&A, 697, A124, doi: 10.1051/0004-6361/202453296

    Lemoine, M., & Rieger, F. 2025, A&A, 697, A124, doi: 10.1051/0004-6361/202453296

    doi:10.1051/0004-6361/202453296 2025

  44. [44]

    P., & Ma, Y

    Li, T. P., & Ma, Y. Q. 1983, ApJ, 272, 317, doi: 10.1086/161295

    doi:10.1086/161295 1983

  45. [45]

    2024, ApJ, 974, 134, doi: 10.3847/1538-4357/ad6e81

    Lian, J.-S., Li, J.-X., Hu, X.-K., et al. 2024, ApJ, 974, 134, doi: 10.3847/1538-4357/ad6e81

    work page doi:10.3847/1538-4357/ad6e81 2024

  46. [46]

    2017, in International Cosmic Ray

    Maier, G., & Holder, J. 2017, in International Cosmic Ray

    2017

  47. [47]

    301, 35th International Cosmic Ray Conference (ICRC2017), 747, doi: 10.22323/1.301.0747 M¨ ucke, A., Engel, R., Rachen, J

    Conference, Vol. 301, 35th International Cosmic Ray Conference (ICRC2017), 747, doi: 10.22323/1.301.0747 M¨ ucke, A., Engel, R., Rachen, J. P., Protheroe, R. J., &

    doi:10.22323/1.301.0747

  48. [48]

    2000, Computer Physics Communications, 124, 290, doi: 10.1016/S0010-4655(99)00446-4

    Stanev, T. 2000, Computer Physics Communications, 124, 290, doi: 10.1016/S0010-4655(99)00446-4

    doi:10.1016/s0010-4655(99)00446-4 2000

  49. [49]

    2025, arXiv e-prints, arXiv:2507.02326, doi: 10.48550/arXiv.2507.02326

    Shoji, A., Fujita, Y., Kawanaka, N., Inoue, S., & Nishiwaki, K. 2025, arXiv e-prints, arXiv:2507.02326, doi: 10.48550/arXiv.2507.02326

    work page doi:10.48550/arxiv.2507.02326 2025

  50. [50]

    E., Taylor, G

    Tremblay, S. E., Taylor, G. B., Ortiz, A. A., et al. 2016, MNRAS, 459, 820, doi: 10.1093/mnras/stw592

    doi:10.1093/mnras/stw592 2016

  51. [51]

    2015, in International Cosmic Ray Conference, Vol

    Vievering, J., & VERITAS Collaboration. 2015, in International Cosmic Ray Conference, Vol. 34, 34th International Cosmic Ray Conference (ICRC2015), 802, doi: 10.22323/1.236.0802

    work page doi:10.22323/1.236.0802 2015

  52. [52]

    P., & Horan, D

    Wakely, S. P., & Horan, D. 2008, International Cosmic Ray Conference, 3, 1341

    2008

  53. [53]

    2003, MNRAS, 340, 793, doi: 10.1046/j.1365-8711.2003.06336.x

    Wang, T.-G., & Zhang, X.-G. 2003, MNRAS, 340, 793, doi: 10.1046/j.1365-8711.2003.06336.x

    arXiv 2003

  54. [54]

    2024, ApJS, 271, 10, doi: 10.3847/1538-4365/ad168c

    Wang, Z.-R., Xue, R., Xiong, D., et al. 2024, ApJS, 271, 10, doi: 10.3847/1538-4365/ad168c

    doi:10.3847/1538-4365/ad168c 2024

  55. [55]

    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, doi: 10.22323/1.301.0824

    doi:10.22323/1.301.0824 2017

  56. [56]

    2010, A&A, 517, A33, doi: 10.1051/0004-6361/201014371

    Younes, G., Porquet, D., Sabra, B., et al. 2010, A&A, 517, A33, doi: 10.1051/0004-6361/201014371

    doi:10.1051/0004-6361/201014371 2010

  57. [57]

    2026, TeV Gamma-Rays from the Low-Luminosity Active Galactic Nucleus NGC 4278: Implications for the Diffuse Neutrino Background, https://arxiv.org/abs/2601.21411

    Yuan, C., & Liu, R.-Y. 2026, TeV Gamma-Rays from the Low-Luminosity Active Galactic Nucleus NGC 4278: Implications for the Diffuse Neutrino Background, https://arxiv.org/abs/2601.21411

    Pith/arXiv arXiv 2026