Pith. sign in

REVIEW 3 major objections 4 minor 2 cited by

IXPE Observation of the Low-Synchrotron Peaked Blazar S4 0954+65 During An Optical-X-ray Flare

T0 review · 3 major / 4 minor · reviewed 2026-08-12 · deepseek-v4-flash

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

Pith's one-line read During an optical-X-ray flare in the blazar S4 0954+65, IXPE found no X-ray polarization, with a 3σ upper limit of 8.8% under the jet-perpendicular alignment assumption.

desk verdict A valuable first IXPE flare observation of an LSP blazar; the hadronic-disfavoring claim is stronger than the non-unique models allow. read the letter →

arxiv 2411.16868 v2 pith:RKMXRXNI submitted 2024-11-25 astro-ph.HE

Pouya M. Kouch , Ioannis Liodakis , Francesco Fenu , Haocheng Zhang , Stella Boula , Riccardo Middei , Laura Di Gesu , Georgios F. Paraschos
show 129 more authors
Iván Agudo Svetlana G. Jorstad Elina Lindfors Alan P. Marscher Henric Krawczynski Michela Negro Kun Hu Dawoon E. Kim Elisabetta Cavazzuti Manel Errando Dmitry Blinov Anastasia Gourni Sebastian Kiehlmann Angelos Kourtidis Nikos Mandarakas Nikolaos Triantafyllou Anna Vervelaki George A. Borman Evgenia N. Kopatskaya Elena G. Larionova Daria A. Morozova Sergey S. Savchenko Andrey A. Vasilyev Ivan S. Troitskiy Tatiana S. Grishina Alexey V. Zhovtan Francisco José Aceituno Giacomo Bonnoli Víctor Casanova Juan Escudero Beatriz Agís-González César Husillos Jorge Otero-Santos Vilppu Piirola Alfredo Sota Ioannis Myserlis Mark Gurwell Garrett K. Keating Ramprasad Rao Emmanouil Angelakis Alexander Kraus Lucio Angelo Antonelli Matteo Bachetti Luca Baldini Wayne H. Baumgartner Ronaldo Bellazzini Stefano Bianchi Stephen D. Bongiorno Raffaella Bonino Alessandro Brez Niccolò Bucciantini Fiamma Capitanio Simone Castellano Chien-Ting Chen Stefano Ciprini Enrico Costa Alessandra De Rosa Ettore Del Monte Niccolò Di Lalla Alessandro Di Marco Immacolata Donnarumma Victor Doroshenko Michal Dovčiak Steven R. Ehlert Teruaki Enoto Yuri Evangelista Sergio Fabiani Riccardo Ferrazzoli Javier A. Garcia Shuichi Gunji Kiyoshi Hayashida Jeremy Heyl Wataru Iwakiri Philip Kaaret Vladimir Karas Fabian Kislat Takao Kitaguchi Jeffery J. Kolodziejczak Fabio La Monaca Luca Latronico Simone Maldera Alberto Manfreda Frédéric Marin Andrea Marinucci Herman L. Marshall Francesco Massaro Giorgio Matt Ikuyuki Mitsuishi Tsunefumi Mizuno Fabio Muleri Chi-Yung Ng Stephen L. O'Dell Nicola Omodei Chiara Oppedisano Alessandro Papitto George G. Pavlov Abel Lawrence Peirson Matteo Perri Melissa Pesce-Rollins Pierre-Olivier Petrucci Maura Pilia Andrea Possenti Juri Poutanen Simonetta Puccetti Brian D. Ramsey John Rankin Ajay Ratheesh Oliver J. Roberts Carmelo Sgrò Patrick Slane Paolo Soffitta Gloria Spandre Douglas A. Swartz Toru Tamagawa Fabrizio Tavecchio Roberto Taverna Yuzuru Tawara Allyn F. Tennant Nicholas E. Thomas Francesco Tombesi Alessio Trois Sergey S. Tsygankov Roberto Turolla Roger W. Romani Jacco Vink Martin C. Weisskopf Kinwah Wu Fei Xie Silvia Zane
This is my paper · ORCID
classification astro-ph.HE
keywords blazarS40954+65X-raypolarimetryIXPEsynchrotronself-ComptonhadronicemissionpolarizationdegreeAGNjets
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

The paper reports the first X-ray polarization measurement of a low-synchrotron-peaked (LSP) blazar caught in an optical-X-ray flare, using IXPE data together with radio, optical, and γ-ray observations. Although the source flared in both X-rays and the optical during the pointing, no X-ray polarization was detected; the tightest constraint, $\Pi_X < 8.8\%$ at 3σ, holds when the X-ray polarization angle is assumed perpendicular to the 43 GHz jet axis. The authors argue that this low X-ray polarization, combined with spectral energy and spectral polarization modeling, strongly disfavors purely hadronic (proton-synchrotron) scenarios, while being consistent with leptonic synchrotron self-Compton (SSC) models. They further trace the flare to a superluminal component in the parsec-scale jet and interpret the smooth optical polarization-angle behavior as evidence for shock acceleration in a magnetic field aligned with the jet.

What carries the argument

The diagnostic machinery is the spectral polarization distribution (SPD), the wavelength-by-wavelength polarization degree, combined with the spectral energy distribution (SED). The paper builds the SPD from contemporaneous IXPE, optical, radio, and Fermi data and compares it against three emission models: single-zone and multi-zone synchrotron self-Compton (SSC) models and a hadronic model dominated by proton and pair synchrotron. The decisive contrast is that SSC predicts the X-ray polarization degree to drop below the optical value ($\Pi_X/\Pi_O \sim 0.3$), whereas hadronic synchrotron predicts comparable polarization in both bands; the measured $\Pi_X < 8.8\%$ against $\Pi_O \approx 14\%$ therefore lands on the leptonic side. A second component is the 43 GHz VLBA imaging, which identifies the superluminal component Q1 as the likely flare site and provides the jet position angle $\Psi_{\mathrm{jet},43} = -42^\circ \pm 7^\circ$ used to fix the X-ray polarization angle in the tightest upper-limit scenario.

What would settle it

A future IXPE observation of S4 0954+65 during a similar optical-X-ray flare that detects X-ray polarization at $\Pi_X > 8.8\%$ (3σ, with the polarization angle fixed perpendicular to the jet axis) would directly contradict the paper's central disfavoring of hadronic emission; equivalently, a published hadronic SED/SPD fit using alternative parameters that yields $\Pi_X < 8.8\%$ would remove the paper's main evidence.

Watch

Extended reading notes

Core claim

The central claim is that in the flaring LSP blazar S4 0954+65 the X-ray polarization degree remained below 8.8% (3σ, under the physically motivated assumption that the X-ray polarization angle is perpendicular to the jet axis), even though the source was in a high optical and X-ray state. The upper limit alone cannot decisively separate leptonic from hadronic emission, but the comparison with the observed optical polarization ($\Pi_O = 14.3\pm4.1\%$) and with model predictions—SSC predicts $\Pi_X < \Pi_O$, while proton and pair synchrotron predicts $\Pi_X \sim \Pi_O$—leads the authors to state that purely hadronic scenarios are strongly disfavored. They additionally associate the flare with the moving 43 GHz component Q1 and propose that a shock propagating through a jet segment with magnetic field parallel to the jet axis produced the flare, with the optical polarization angle staying perpendicular to the jet axis during the event.

Load-bearing premise

The disfavoring of hadronic models rests on a hand-picked set of model parameters (Table 3) that the authors state are not fitted to the data and are not a unique solution; a different hadronic parameter choice that lowered the predicted X-ray polarization below the 8.8% upper limit would overturn the conclusion.

Editorial extensions

If this is right

  • If the low X-ray polarization holds, purely hadronic proton-synchrotron models become difficult to sustain for this source, and by extension for similar LSP blazars observed by IXPE.
  • The coincidence of optical and X-ray flares with a superluminal jet component supports co-spatial emission from a moving shock, making multi-zone or stratified-jet SSC models the more natural framework for LSP flares.
  • A stable optical polarization angle during the flare, oriented perpendicular to the jet, provides a direct geometric probe of the magnetic field orientation in the flaring region: field lines parallel to the jet axis.
  • The paper's upper limits add to the growing IXPE sample showing $\Pi_X < \Pi_O$ in low-synchrotron-peaked sources, which is the expected sign of SSC rather than hadronic or anisotropic-EC emission.
  • Future flare-triggered IXPE observations of LSP blazars can use the perpendicular-alignment assumption to obtain roughly factor-of-1.6 tighter constraints on $\Pi_X$ than unconstrained fits.

Reading between the lines

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

  • A direct testable extension is to monitor S4 0954+65 through a similar flare with a longer IXPE exposure: if SSC is correct, the X-ray polarization should eventually be detected at the few-percent level, while hadronic models with $\Pi_X \sim \Pi_O$ predict a value above the current 8.8% limit.
  • The same SPD comparison could be applied to other LSP blazars with bright optical polarization, where the contrast between SSC and hadronic predictions is largest; since the paper's model parameters are explicitly not unique, a broader parameter scan would strengthen or weaken the hadronic disfavoring.
  • If future observations find that the optical and X-ray polarization angles rotate together during flares, that would tie the high-energy emission to the same magnetic-field geometry as the synchrotron component, further anchoring the leptonic interpretation.
  • The paper implicitly assumes the X-ray emission comes from the same region as the optical flare; if a future campaign resolves a separate X-ray-emitting zone, the polarization comparison would need to be revisited.
Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

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

Referee Report

3 major / 4 minor

Summary. The paper presents the first IXPE X-ray polarization measurement of the LSP blazar S4 0954+65 during a flaring optical and X-ray state, together with a contemporaneous multiwavelength campaign including optical, radio, VLBA, X-ray, and gamma-ray observations. IXPE does not detect X-ray polarization; the authors report a 3 sigma upper limit of 14% for the full observation and a tighter limit of 8.8% when the X-ray polarization angle is fixed perpendicular to the parsec-scale jet axis. The optical polarization angle is found to rotate and to be perpendicular to the jet axis during the flare, and the flare is associated with a superluminal VLBA component. The authors model the SED and spectral polarization distribution with single-zone and multi-zone SSC models and a proton-synchrotron hadronic model, concluding that hadronic scenarios for the X-ray emission are tentatively disfavored, with the abstract using 'tentatively' while the discussion text uses 'strongly disfavor'.

Significance. If the conclusions hold, this is a useful addition to the growing IXPE sample of low- and intermediate-synchrotron-peaked blazars, and it is the first IXPE polarization study of a purely LSP blazar in an outburst state. The paper's strengths are the careful IXPE data reduction, the cross-check between the PCUBE algorithm and spectro-polarimetric fitting, the dense contemporaneous multiwavelength coverage, and the explicit caveats in the modeling section. The observational result, a robust upper limit on X-ray polarization during a flare, is valuable regardless of the model interpretation. The main scientific conclusion, however, is model-dependent and rests on a representative, non-unique hadronic model parameter set and on a geometric assumption for the X-ray polarization angle, so the strength of the conclusion needs to be matched to the strength of those assumptions.

major comments (3)
  1. [Section 5, Fig. 4 bottom, Table 3] The claim that hadronic scenarios are 'strongly disfavored' is load-bearing and depends on the hadronic model predicting ΠX ≈ ΠO ≈ 14%, which exceeds the IXPE upper limit of 8.8%. The Table 3 note explicitly states that the model parameters 'are not fitted to the data' and are 'one representation of the data and not a unique solution.' The X-ray polarization degree in proton-synchrotron models depends on B, blob radius R, proton injection luminosity and spectral index, γ_p,max, and the assumed magnetic-field order; a different hadronic parameter set reproducing the SED could plausibly yield ΠX below 8.8%, for instance through a more extended or less ordered emission region or a contribution from pair-synchrotron emission. Without a parameter scan or other demonstration that the high ΠX prediction is robust across the hadronic parameter space, the conclusion should be softened to 'tentatively disfavored' throughout, as the abstract already does.
  2. [Section 2.1, Table 1] The most constraining upper limit, ΠX < 8.8%, is obtained only after fixing the X-ray polarization angle perpendicular to the 43 GHz jet position angle; the unconstrained 3σ upper limit is 14%. The hadronic model considered predicts ΨX perpendicular to the jet, so this assumption is physically motivated, but the paper itself cautions in Section 5 that without a polarization detection any polarization-angle inference should be treated with caution. Because the hadronic disfavoring hinges on comparing a predicted ΠX ≈ 14% with the 8.8% limit, the conclusion is conditional on the assumed angle. The authors should state this conditionality explicitly or demonstrate that the conclusion is insensitive to reasonable deviations of ΨX from the assumed perpendicular direction.
  3. [Section 4, Fig. 4, Table 3] The statement that all three models 'can adequately explain' the SED is not supported by a quantitative goodness-of-fit comparison; the parameters are hand-selected and the models are not fitted to the data. Figure 4 therefore illustrates representative cases rather than providing a model comparison. This is acceptable for an exploratory study, but the text should be explicit that no fit statistic was computed and that the discriminating power of the SPD comparison is limited by the representativeness of the chosen parameters. This is particularly important because the main conclusion about hadronic models depends on the SPD of a single hadronic parameterization.
minor comments (4)
  1. [Abstract and Section 5] The abstract says the results 'tentatively disfavor' hadronic models, while Section 5 states that 'they strongly disfavor purely hadronic scenarios'; this inconsistency should be resolved, especially in light of the non-unique model parameters.
  2. [Fig. 3 caption] The Fig. 3 caption contains a typo: 'The bottom-left white circle is has a radius' should be 'The bottom-left white circle has a radius'. The caption also quotes the jet direction as -42° ± 6° while Section 3.3 quotes -42° ± 7°; please make these consistent.
  3. [Section 4] The abstract describes the hadronic model as 'proton and pair synchrotron', but Section 4 says the hadronic model 'mainly includes proton-synchrotron radiation'. Please clarify whether pair-synchrotron emission is included in the model and, if so, how it affects the predicted polarization.
  4. [Section 5] The argument that co-spatial optical and X-ray flares conflict with hadronic scenarios relies on the assumption that the flares are co-spatial based on peak coincidence. This is a reasonable working hypothesis, but the wording 'conflicts with a hadronic scenario' is stronger than the evidence supports; a softer phrasing such as 'is in tension with' would be more appropriate.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the X-ray polarization upper limit is an external observable and the model parameters are not fitted to it.

full rationale

The paper's central comparison is between an independently measured IXPE X-ray polarization upper limit and the spectral polarization distributions predicted by leptonic and hadronic emission models. The model parameters in Table 3 are explicitly stated to be 'not fitted to the data' and are presented as 'one representation of the data and not a unique solution,' so the hadronic SPD prediction is not obtained by fitting to the polarization observable it is used to test. The tighter upper limit of ΠX < 8.8% is derived by fixing ΨX perpendicular to the jet axis, an assumption justified physically from the contemporaneous optical polarization angle and the inferred magnetic field orientation; this is a hypothesis-testing procedure rather than a definitional identity. The conclusion that purely hadronic scenarios are disfavored does depend on the chosen hadronic parameter set, and a robustness caveat about parameter non-uniqueness is legitimate, but that is a model-validity concern, not circularity. Self-citations to prior IXPE analyses and modeling codes are used as methodology references and are not load-bearing in a way that reduces the central result to the paper's own assumptions. No equation or fitted parameter is renamed as a prediction, and no uniqueness claim is imported from the authors' prior work. The derivation chain is therefore self-contained in the relevant sense.

Assumptions & free parameters 10 free parameters · 5 assumptions · 0 invented entities

The central model-based conclusion relies on emission models (SSC and hadronic) with a number of hand-picked parameters that are not uniquely constrained by the data. The paper does not introduce new theoretical entities. The main additional assumptions are the standard applicability of the models and the use of the measured jet position angle as a reference for polarization angle scenarios.

free parameters (10)
  • Hadronic model magnetic field B = 100 G
    Hand-chosen in Table 3 to reproduce the SED; sets the proton synchrotron frequency and the predicted X-ray polarization.
  • Hadronic model proton luminosity Lp = 3e49 erg/s
    Chosen to match the high-energy SED; affects the hadronic spectral polarization distribution amplitude.
  • Hadronic model proton maximum Lorentz factor gamma_p,max = 3e8
    Sets the high-energy cutoff of proton synchrotron; chosen by hand.
  • Hadronic model proton spectral index p_p = 2.37
    Chosen to reproduce the SED slope; not fit.
  • Single-zone SSC magnetic field B = 0.028 G
    Hand-chosen in Table 3; determines the SSC polarization fraction.
  • Single-zone SSC electron injection luminosity L_e = 2.6e46 erg/s
    Chosen to fit the SED; non-unique.
  • Single-zone SSC electron maximum Lorentz factor gamma_e,max = 2e4
    Sets the SED high-energy cut; chosen by hand.
  • Single-zone SSC electron spectral index p_e = 2.2
    Chosen to match the SED slope.
  • Multi-zone SSC magnetic field B = 0.12 G
    Chosen for the multi-zone model in Table 3.
  • Multi-zone SSC jet power W_j = 5e45 erg/s
    Chosen to reproduce the SED; the paper notes the models are not fitted and not unique.
assumptions (5)
  • domain assumption Standard synchrotron self-Compton and hadronic (proton synchrotron) emission physics are valid frameworks for blazar X-ray emission.
    The paper relies on these models in Section 4 without deriving them from first principles.
  • domain assumption The IXPE polarization analysis methods (Kislat et al. 2015, ixpeobssim) are unbiased and correctly implemented.
    Standard data reduction assumed in Section 2.1; no independent verification in the paper.
  • domain assumption The measured 43 GHz jet position angle of -42 degrees represents the jet axis.
    Used in Section 3.3 and Table 1 to define the parallel and perpendicular reference directions for polarization angles.
  • ad hoc to paper The X-ray polarization angle is assumed perpendicular to the jet axis or to the optical polarization angle to obtain the most constraining upper limits.
    This is an unfitted assumption in Section 2.1 and Table 1; the authors caution that without a significant detection, any polarization angle inference should be treated with caution.
  • ad hoc to paper The optical and X-ray flares are co-spatial based on the coincidence of their peaks.
    Inferred in Section 5; load-bearing for associating the polarization properties with the X-ray emission region and for the hadronic model argument.

how reviews work

0 comments
Cite this review

Pith. "Pith review of IXPE Observation of the Low-Synchrotron Peaked Blazar S4 0954+65 During An Optical-X-ray Flare." pith.science (2026). https://pith.science/paper/RKMXRXNI

@misc{pith2026241116868,
  author       = {Pith},
  title        = {Pith review of: IXPE Observation of the Low-Synchrotron Peaked Blazar S4 0954+65 During An Optical-X-ray Flare},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/RKMXRXNI}},
  note         = {Machine review of arXiv:2411.16868}
}
abstract

The X-ray polarization observations made possible with the Imaging X-ray Polarimetry Explorer (IXPE) offer new ways of probing high-energy emission processes in astrophysical jets from blazars. Here we report on the first X-ray polarization observation of the blazar S4 0954+65 in a high optical and X-ray state. During our multi-wavelength campaign on the source, we detected an optical flare whose peak coincided with the peak of an X-ray flare. This optical-X-ray flare most likely took place in a feature moving along the parsec-scale jet, imaged at 43 GHz by the Very Long Baseline Array. The 43 GHz polarization angle of the moving component underwent a rotation near the time of the flare. In the optical band, prior to the IXPE observation, we measured the polarization angle to be aligned with the jet axis. In contrast, during the optical flare the optical polarization angle was perpendicular to the jet axis; after the flare, it reverted to being parallel to the jet axis. Due to the smooth behavior of the optical polarization angle during the flare, we favor shocks as the main acceleration mechanism. We also infer that the ambient magnetic field lines in the jet were parallel to the jet position angle. The average degree of optical polarization during the IXPE observation was (14.3$\pm$4.1)%. Despite the flare, we only detected an upper limit of 14% (at 3$\sigma$ level) on the X-ray polarization degree; although a reasonable assumption on the X-ray polarization angle results in an upper limit of 8.8% ($3\sigma$). We model the spectral energy distribution (SED) and spectral polarization distribution (SPD) of S4 0954+65 with leptonic (synchrotron self-Compton) and hadronic (proton and pair synchrotron) models. The constraints we obtain with our combined multi-wavelength polarization observations and SED modeling tentatively disfavor hadronic models for the X-ray emission in S4 0954+65.

Figures

Figures reproduced from arXiv: 2411.16868 by the authors.

Figure 1
Figure 1. X-ray photon counts from S4 0954+65 as detected by IXPE plot￾ted against time (MJD). IXPE observed the source from MJD 60089 un￾til 60098. The X-ray flux experiences several minor flares and a major one. In this paper, we focus on the major flare which occurs approxi￾mately from MJD 60094 to 60096 (peaking at MJD 60095, 2023 May 31). consider three time intervals: the full IXPE exposure (from MJD 60089 to 60098); th… view at source ↗
Figure 2
Figure 2. Contemporaneous radio and optical observations of S4 0954+65. From top to bottom, the panels show optical brightness in magnitudes, polarization degree (Π) in %, and polarization angle (Ψ) in degrees. The grey shaded area (vertical) marks the duration of the IXPE observation (MJD 60089-60098). In the middle panel, the red and blue shaded areas (horizontal) are centered on the average ΠO and ΠR within the IXPE observ… view at source ↗
Figure 3
Figure 3. 43 GHz total intensity (Stokes I) VLBA images of S4 0954+65. Panels (A), (B), (C), and (D) show the parsec-scale maps of the compact core of the source from data obtained on 2023 April 2 (MJD 60036; about two months before the IXPE observation), 2023 May 21 (MJD 60085; five days before the IXPE pointing), 2023 June 1 (MJD 60096; during the IXPE pointing and in the vicinity of the peak of the optical-X-ray flare), an… view at source ↗
Figures from the paper (2 more)
Figure 4
Figure 4. Figure 4: Top: Spectral energy distribution (SED) of S4 0954+65. Bottom: Spectral polarization distribution (SPD) of S4 0954+65. In both panels, the cyan data points show the median and standard deviation values at different frequencies during the IXPE exposure. The archival obs…
Figure 5
Figure 5. Figure 5: Rough general timeline of the MWL observations of S4 0954+65. time or energy within the IXPE observing window. To obtain more constraining upper limits, we fix the X-ray polarization angle (ΨX) to values motivated by the direction of the jet on the sky or the optical p…

Discussion (0). Continue with ORCID to comment.

Forward citations

Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. High optical to X-ray polarization ratio reveals Compton scattering in BL Lacertae's jet

    astro-ph.HE 2025-05 conditional novelty 7.0 of 10

    BL Lacertae's record optical polarization with a very low X-ray polarization upper limit favors leptonic Compton-scattering emission and disfavors hadronic models.

  2. Decoding the jet of BL Lacertae using relativistic magneto-hydrodynamics

    astro-ph.HE 2026-08 conditional novelty 6.0 of 10

    The highest optical polarization flare ever seen from a blazar is explained by a sweeping, Doppler-boosted helical jet component, and the jet appears proton-dominated.

Reference graph

Works this paper leans on

95 extracted references · 41 canonical work pages · cited by 2 Pith papers

  1. [1]

    A., Ackermann, M., Ajello, M., et al

    Abdo, A. A., Ackermann, M., Ajello, M., et al. 2010, ApJ, 710, 1271

    2010

  2. [2]

    2020, ApJS, 247, 33

    Abdollahi, S., Acero, F., Ackermann, M., et al. 2020, ApJS, 247, 33

    2020

  3. [3]

    2015, MNRAS, 451, L21

    Bachev, R. 2015, MNRAS, 451, L21

    2015

  4. [4]

    D., et al

    Baldini, L., Bucciantini, N., Lalla, N. D., et al. 2022, SoftwareX, 19, 101194

    2022

  5. [5]

    H., Digel, S

    Ballet, J., Burnett, T. H., Digel, S. W., & Lott, B. 2020, arXiv e-prints, arXiv:2005.11208 Balokovi´c, M., Paneque, D., Madejski, G., et al. 2016, ApJ, 819, 156 Becerra González, J., Acosta-Pulido, J. A., Boschin, W., et al. 2021, MNRAS, 504, 5258

    arXiv 2020

  6. [6]

    C., Rudak, B., & Sikora, M

    Begelman, M. C., Rudak, B., & Sikora, M. 1990, ApJ, 362, 38

    1990

  7. [7]

    Begelman, M. C. & Sikora, M. 1987, ApJ, 322, 650

    1987

  8. [8]

    C., Kulkarni, S

    Bellm, E. C., Kulkarni, S. R., Graham, M. J., et al. 2019, PASP, 131, 018002

    2019

Show all 95 references
  1. [9]

    & Eichler, D

    Blandford, R. & Eichler, D. 1987, Phys. Rep., 154, 1

    1987

  2. [10]

    2019, ARA&A, 57, 467

    Blandford, R., Meier, D., & Readhead, A. 2019, ARA&A, 57, 467

    2019

  3. [11]

    2022, arXiv e-prints, arXiv:2204.12242

    Boettcher, M., Fu, M., Govenor, T., King, Q., & Roustazadeh, P. 2022, arXiv e-prints, arXiv:2204.12242

    2022 arXiv

  4. [12]

    1970, A&A, 7, 292

    Bonometto, S., Cazzola, P., & Saggion, A. 1970, A&A, 7, 292

    1970

  5. [13]

    & Saggion, A

    Bonometto, S. & Saggion, A. 1973, A&A, 23, 9 Böttcher, M. 2019, Galaxies, 7, 20 Böttcher, M., Reimer, A., Sweeney, K., & Prakash, A. 2013, ApJ, 768, 54

    1973

  6. [14]

    A., Johnson, M

    Chael, A. A., Johnson, M. D., Narayan, R., et al. 2016, ApJ, 829, 11

    2016

  7. [15]

    J., Liodakis, I., Middei, R., et al

    Chen, C.-T. J., Liodakis, I., Middei, R., et al. 2024, ApJ, 974, 50

    2024

  8. [16]

    Cohen, M. H. & Savolainen, T. 2020, A&A, 636, A79

    2020

  9. [17]

    & Sironi, L

    Comisso, L. & Sironi, L. 2018, Phys. Rev. Lett., 121, 255101

    2018

  10. [18]

    1996, A&A, 306, 395

    Cristiani, S., Trentini, S., La Franca, F., et al. 1996, A&A, 306, 395

    1996

  11. [19]

    H., Hu, S

    Deng, J. H., Hu, S. M., Jiang, Z. J., Xiang, Y . C., & Zhou, R. X. 2022, Ap&SS, 367, 43

    2022

  12. [20]

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

    Dermer, C. D., Schlickeiser, R., & Mastichiadis, A. 1992, A&A, 256, L27 Di Gesu, L., Donnarumma, I., Tavecchio, F., et al. 2022a, ApJ, 938, L7 Di Gesu, L., Marshall, H. L., Ehlert, S. R., et al. 2023, Nature Astronomy, 7, 1245 Di Gesu, L., Tavecchio, F., Donnarumma, I., et al....

    1992

  13. [21]

    Dickey, J. M. & Lockman, F. J. 1990, ARA&A, 28, 215

    1990

  14. [22]

    R., Ferrazzoli, R., Marinucci, A., et al

    Ehlert, S. R., Ferrazzoli, R., Marinucci, A., et al. 2022, ApJ, 935, 116

    2022

  15. [23]

    R., Liodakis, I., Middei, R., et al

    Ehlert, S. R., Liodakis, I., Middei, R., et al. 2023, ApJ, 959, 61

    2023

  16. [24]

    P., et al

    Errando, M., Liodakis, I., Marscher, A. P., et al. 2024, ApJ, 963, 5

    2024

  17. [25]

    C., Kochenov, P

    Gabuzda, D. C., Kochenov, P. Y ., Kollgaard, R. I., & Cawthorne, T. V . 2000, MNRAS, 315, 229

    2000

  18. [26]

    2004, ApJ, 611, 1005

    Gehrels, N., Chincarini, G., Giommi, P., et al. 2004, ApJ, 611, 1005

    2004

  19. [27]

    2011, MNRAS, 414, 2674

    Ghisellini, G., Tavecchio, F., Foschini, L., & Ghirlanda, G. 2011, MNRAS, 414, 2674

    2011

  20. [28]

    2020, Physics of Plasmas, 27, 080501 HI4PI Collaboration, Ben Bekhti, N., Flöer, L., et al

    Guo, F., Liu, Y .-H., Li, X., et al. 2020, Physics of Plasmas, 27, 080501 HI4PI Collaboration, Ben Bekhti, N., Flöer, L., et al. 2016, A&A, 594, A116

    2020

  21. [29]

    Ho, P. T. P., Moran, J. M., & Lo, K. Y . 2004, ApJ, 616, L1

    2004

  22. [30]

    F., Aller, H

    Hovatta, T., Aller, M. F., Aller, H. D., et al. 2014, AJ, 147, 143

    2014

  23. [31]

    & Lindfors, E

    Hovatta, T. & Lindfors, E. 2019, New A Rev., 87, 101541

    2019

  24. [32]

    2016, A&A, 596, A78 IceCube Collaboration, Aartsen, M

    Hovatta, T., Lindfors, E., Blinov, D., et al. 2016, A&A, 596, A78 IceCube Collaboration, Aartsen, M. G., Ackermann, M., et al. 2018, Science, 361, eaat1378

    2016

  25. [33]

    2001, A&A, 365, L1

    Jansen, F., Lumb, D., Altieri, B., et al. 2001, A&A, 365, L1

    2001

  26. [34]

    W., O’Dell, S

    Jones, T. W., O’Dell, S. L., & Stein, W. A. 1974, ApJ, 188, 353

    1974

  27. [35]

    & Marscher, A

    Jorstad, S. & Marscher, A. 2016, Galaxies, 4, 47

    2016

  28. [36]

    G., Marscher, A

    Jorstad, S. G., Marscher, A. P., Morozova, D. A., et al. 2017, ApJ, 846, 98

    2017

  29. [37]

    G., Marscher, A

    Jorstad, S. G., Marscher, A. P., Stevens, J. A., et al. 2007, AJ, 134, 799

    2007

  30. [38]

    Kaastra, J. S. 2017, A&A, 605, A51

    2017

  31. [39]

    E., Di Gesu, L., Liodakis, I., et al

    Kim, D. E., Di Gesu, L., Liodakis, I., et al. 2024, A&A, 681, A12

    2024

  32. [40]

    2015, Astroparticle Physics, 68, 45

    Kislat, F., Clark, B., Beilicke, M., & Krawczynski, H. 2015, Astroparticle Physics, 68, 45

    2015

  33. [41]

    P., Wegner, R., et al

    Kraus, A., Krichbaum, T. P., Wegner, R., et al. 2003, A&A, 401, 161

    2003

  34. [42]

    2014, The Astronomer’s Telegram, 6709, 1

    Krauss, F. 2014, The Astronomer’s Telegram, 6709, 1

    2014

  35. [43]

    2012, ApJ, 744, 30

    Krawczynski, H. 2012, ApJ, 744, 30

    2012

  36. [44]

    Laing, R. A. 1980, MNRAS, 193, 439

    1980

  37. [45]

    J., & Penston, M

    Lawrence, A., Walker, D., Rowan-Robinson, M., Leech, K. J., & Penston, M. V . 1986, MNRAS, 219, 687

    1986

  38. [46]

    L., & Romani, R

    Liodakis, I., Peirson, A. L., & Romani, R. W. 2019, ApJ, 880, 29

    2019

  39. [47]

    & Petropoulou, M

    Liodakis, I. & Petropoulou, M. 2020, ApJ, 893, L20

    2020

  40. [48]

    2023, A&A, 680, L11

    Liodakis, I., Shablovinskaya, E., Blinov, D., et al. 2023, A&A, 680, L11

    2023

  41. [49]

    L., Aller, M

    Lister, M. L., Aller, M. F., Aller, H. D., et al. 2018, ApJS, 234, 12

    2018

  42. [50]

    I., & Gabuzda, D

    Lyutikov, M., Pariev, V . I., & Gabuzda, D. C. 2005, MNRAS, 360, 869 MAGIC Collaboration, Ahnen, M. L., Ansoldi, S., et al. 2018, A&A, 617, A30

    2005

  43. [51]

    & Biermann, P

    Mannheim, K. & Biermann, P. L. 1989, A&A, 221, 211

    1989

  44. [52]

    1992, ApJ, 397, L5

    Maraschi, L., Ghisellini, G., & Celotti, A. 1992, ApJ, 397, L5

    1992

  45. [53]

    P., Liu, X., et al

    Marchili, N., Krichbaum, T. P., Liu, X., et al. 2012, A&A, 542, A121

    2012

  46. [54]

    Marrone, D. P. & Rao, R. 2008, in Society of Photo-Optical Instrumentation En- gineers (SPIE) Conference Series, V ol. 7020, Millimeter and Submillimeter Detectors and Instrumentation for Astronomy IV , ed. W. D. Duncan, W. S

    2008

  47. [55]

    Marscher, A. P. 2014, ApJ, 780, 87

    2014

  48. [56]

    P., Di Gesu, L., Jorstad, S

    Marscher, A. P., Di Gesu, L., Jorstad, S. G., et al. 2024, Galaxies, 12, 50

    2024

  49. [57]

    Marscher, A. P. & Gear, W. K. 1985, ApJ, 298, 114

    1985

  50. [58]

    P., Jorstad, S

    Marscher, A. P., Jorstad, S. G., D’Arcangelo, F. D., et al. 2008, Nature, 452, 966

    2008

  51. [59]

    P., Jorstad, S

    Marscher, A. P., Jorstad, S. G., Larionov, V . M., et al. 2010, ApJ, 710, L126

    2010

  52. [60]

    P., Jorstad, S

    Marscher, A. P., Jorstad, S. G., Mattox, J. R., & Wehrle, A. E. 2002, ApJ, 577, 85

    2002

  53. [61]

    L., Liodakis, I., Marscher, A

    Marshall, H. L., Liodakis, I., Marscher, A. P., et al. 2024, ApJ, 972, 74

    2024

  54. [62]

    Mead, A. R. G., Ballard, K. R., Brand, P. W. J. L., et al. 1990, A&AS, 83, 183

    1990

  55. [63]

    A., Larionov, V

    Morozova, D. A., Larionov, V . M., Troitsky, I. S., et al. 2014, AJ, 148, 42

    2014

  56. [64]

    D., Aller, M

    Mukherjee, R., Aller, H. D., Aller, M. F., et al. 1995, ApJ, 445, 189

    1995

  57. [65]

    2024, The physics of AGN jets revealed by full-Stokes monitoring at mm and cm wavelengths

    Myserlis, I. 2024, The physics of AGN jets revealed by full-Stokes monitoring at mm and cm wavelengths

    2024

  58. [66]

    2018, A&A, 609, A68

    Myserlis, I., Angelakis, E., Kraus, A., et al. 2018, A&A, 609, A68

    2018

  59. [67]

    O., et al

    Nilsson, K., Lindfors, E., Takalo, L. O., et al. 2018, A&A, 620, A185

    2018

  60. [68]

    Padovani, P., Resconi, E., Giommi, P., Arsioli, B., & Chang, Y . L. 2016, MN- RAS, 457, 3582

    2016

  61. [69]

    2023, A&A, 679, A28

    Pandey, A., Bachev, R., Czerny, B., et al. 2023, A&A, 679, A28

    2023

  62. [70]

    L., Negro, M., Liodakis, I., et al

    Peirson, A. L., Negro, M., Liodakis, I., et al. 2023, ApJ, 948, L25

    2023

  63. [71]

    Peirson, A. L. & Romani, R. W. 2019, ApJ, 885, 76

    2019

  64. [72]

    2020, ApJ, 891, 115

    Petropoulou, M., Murase, K., Santander, M., et al. 2020, ApJ, 891, 115

    2020

  65. [73]

    2004, MNRAS, 351, 161

    Piconcelli, E., Jimenez-Bailón, E., Guainazzi, M., et al. 2004, MNRAS, 351, 161

    2004

  66. [74]

    1994, ApJS, 92, 607

    Poutanen, J. 1994, ApJS, 92, 607

    1994

  67. [75]

    B., Aller, H

    Pushkarev, A. B., Aller, H. D., Aller, M. F., et al. 2023, MNRAS, 520, 6053

    2023

  68. [76]

    M., Villata, M., Carnerero, M

    Raiteri, C. M., Villata, M., Carnerero, M. I., et al. 2023, MNRAS, 526, 4502

    2023

  69. [77]

    M., Villata, M., Larionov, V

    Raiteri, C. M., Villata, M., Larionov, V . M., et al. 2021, MNRAS, 504, 5629

    2021

  70. [78]

    M., Villata, M., Tosti, G., et al

    Raiteri, C. M., Villata, M., Tosti, G., et al. 1999, A&A, 352, 19

    1999

  71. [79]

    N., Rajarshi, C

    Ramaprakash, A. N., Rajarshi, C. V ., Das, H. K., et al. 2019, MNRAS, 485, 2355

    2019

  72. [80]

    R., Prince, R., Khatoon, R., & Bose, D

    Sharma, A., Kamaram, S. R., Prince, R., Khatoon, R., & Bose, D. 2024, MN- RAS, 527, 2672

    2024

  73. [81]

    C., & Rees, M

    Sikora, M., Begelman, M. C., & Rees, M. J. 1994, ApJ, 421, 153 Strüder, L., Briel, U., Dennerl, K., et al. 2001, A&A, 365, L18

    1994

  74. [82]

    T., Becerra Gonzalez, J., Itoh, R., et al

    Tanaka, Y . T., Becerra Gonzalez, J., Itoh, R., et al. 2016, PASJ, 68, 51

    2016

  75. [83]

    A., Boggs, S

    Tomsick, J. A., Boggs, S. E., Zoglauer, A., et al. 2023, arXiv e-prints, arXiv:2308.12362

    2023 arXiv

  76. [84]

    L., Denneau, L., Heinze, A

    Tonry, J. L., Denneau, L., Heinze, A. N., et al. 2018, PASP, 130, 064505

    2018

  77. [85]

    Ulrich, M.-H., Maraschi, L., & Urry, C. M. 1997, ARA&A, 35, 445

    1997

  78. [86]

    A., Ferland, G

    Verner, D. A., Ferland, G. J., Korista, K. T., & Yakovlev, D. G. 1996, ApJ, 465, 487

    1996

  79. [87]

    R., Jorstad, S

    Weaver, Z. R., Jorstad, S. G., Marscher, A. P., et al. 2022, ApJS, 260, 12

    2022

  80. [88]

    C., Soffitta, P., Baldini, L., et al

    Weisskopf, M. C., Soffitta, P., Baldini, L., et al. 2022, Journal of Astronomical

    2022

  81. [89]

    2000, ApJ, 542, 914

    Wilms, J., Allen, A., & McCray, R. 2000, ApJ, 542, 914

    2000

  82. [90]

    & Böttcher, M

    Zhang, H. & Böttcher, M. 2013, ApJ, 774, 18

    2013

  83. [91]

    2024, ApJ, 967, 93

    Zhang, H., Böttcher, M., & Liodakis, I. 2024, ApJ, 967, 93

    2024

  84. [92]

    2016, ApJ, 829, 69

    Zhang, H., Diltz, C., & Böttcher, M. 2016, ApJ, 829, 69

    2016

  85. [93]

    2019, ApJ, 876, 109

    Zhang, H., Fang, K., Li, H., et al. 2019, ApJ, 876, 109

    2019

  86. [94]

    2020, ApJ, 901, 149

    Zhang, H., Li, X., Giannios, D., et al. 2020, ApJ, 901, 149

    2020

  87. [95]

    P., Guo, F., et al

    Zhang, H., Marscher, A. P., Guo, F., et al. 2023, ApJ, 949, 71 1 Department of Physics and Astronomy, University of Turku, FI- 20014 Turku, Finland 2 Finnish Centre for Astronomy with ESO (FINCA), Quantum, Vesilinnantie 5, University of Turku, FI-20014 Turku, Finland 3 Institu...

    2023

Pith tools

Reviewed August 12, 2026 · model on record in the stance chip above.