Pith. sign in

REVIEW 5 major objections 5 minor 14 references

A 25 PeV neutron jet from an SS433 flare explains its distant TeV gamma-ray beams

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

2026-08-03 17:59 UTC pith:JRYMD4PI

load-bearing objection A testable idea — a ~25 PeV neutron beam from a past SS433 flare — but no predicted gamma-ray flux, so the explanatory claim is unsubstantiated. the 5 major comments →

arxiv 2512.07012 v1 pith:JRYMD4PI submitted 2025-12-07 astro-ph.HE astro-ph.GAastro-ph.IMhep-ph

SS433 PeV neutron jet feeding the far TeV gamma beam

Daniele Fargion , Pier Giorgio De Sanctis Lucentini , Sara Turriziani , Danila Sopin , Maxim Yu. Khlopov This is my paper
classification astro-ph.HE astro-ph.GAastro-ph.IMhep-ph PACS 95.30.Gv95.85.Pw98.70.Rz
keywords SS433microquasar jetsPeV neutron beamtens of TeV gamma raysinverse Compton scatteringDelta resonanceultraviolet flareW50 nebula
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 a rare flare in the microquasar SS433, roughly a century ago, ejected a narrow jet of ultra-high-energy neutrons at around 25 PeV. Those neutrons travel about 75 light-years before decaying, and the electrons produced in their decay scatter ambient photons up to tens of TeV, matching the disconnected gamma-ray tails that H.E.S.S., HAWC, and LHAASO have detected far from the inner jets. The key move is converting a charged proton jet into a neutral neutron beam during a hot ultraviolet flare, so that magnetic fields cannot bend or break the beam until it decays far away. If correct, this would solve the puzzle of how the jets remain collimated over hundreds of light-years.

Core claim

The paper proposes that SS433's known relativistic proton jet interacted with a dense bath of thermal ultraviolet photons during a nova-like flare about 75–150 years ago, producing Delta resonances that decayed into a collimated beam of tens-of-PeV neutrons. A 25 PeV neutron has a mean decay length of about 75 light-years; its beta-decay electrons then inverse-Compton scatter ambient photons to tens of TeV, reproducing the spatially separated, twin gamma-ray beams observed at roughly 75–150 light-years from SS433. The quantitative chain includes a tuned resonance energy (30 eV photons for 25 PeV protons), a flare luminosity of about 3.6×10^40 erg/s, and a conversion probability in the disk r

What carries the argument

The central mechanism is the photo-nuclear Delta resonance: a ~27 PeV proton colliding with a ~28–30 eV thermal photon creates a Δ+ resonance, which decays into a neutron and a pion (or a proton and a neutral pion). The resulting neutron, being electrically neutral, travels undeflected through the galactic magnetic field for its ~877-second rest-frame lifetime, covering ~75 light-years at 25 PeV. The decay electrons then inverse-Compton scatter ambient radiation to tens of TeV, producing the observed disconnected gamma-ray beams.

Load-bearing premise

The entire argument hinges on the assumption that SS433 experienced a nova-like ultraviolet flare a century or so ago, with a luminosity and duration that left no well-attested historical record; without that flare, there is no photon bath to convert protons into neutrons.

What would settle it

Searching historical photographic plate archives in the SS433 direction for a transient brightening of magnitude ~10–12 (from a 3.6×10^40 erg/s UV flare at 5 kpc) around 75–150 years ago would settle the model; absence of any such flare would directly falsify the proposed neutron-beam production.

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

If this is right

  • The observed TeV gamma-ray beams at 75 and 150 light-years from SS433 would be the decay signatures of a single past neutron jet, not the consequence of in-situ shock re-acceleration or re-collimation.
  • The model fixes the flare epoch to roughly 75–150 years ago and predicts that the flare's ultraviolet radiation would have been bright enough to be detectable in historical photographic plate archives from that direction.
  • If other microquasars undergo similar flares, they should also exhibit disconnected TeV or PeV gamma-ray beams at distances set by the neutron energy, providing a testable population signature.
  • The same beam would produce a burst of PeV and sub-PeV neutrinos (from charged pions in the same Delta decays) if pointed toward Earth, potentially connecting to IceCube's observed PeV neutrino events.
  • The model predicts a specific spectral and spatial correlation: the TeV flux should be aligned exactly along the original jet axis and should have a sharp cutoff at the neutron decay distance, unlike a continuous shock-accelerated emission.

Where Pith is reading between the lines

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

  • The paper's mechanism generalizes the GZK cut-off idea to a much smaller, time-variable photon bath; the same Delta-resonance conversion could operate in other binary systems with active jet–flare interactions, making them transient PeV neutron factories.
  • Because the neutron beam is neutral, the angular width of the resulting TeV beam is set only by the parent proton beam's opening angle and the neutron's transverse momenta from Delta decay; this could be used to constrain the flare geometry more tightly than current data allow.
  • The model implicitly requires that the flare's photon bath cover the full jet cross-section and last longer than the resonance crossing time; if future searches find no historical flare signature, the entire scenario would be ruled out, which is a clean way to falsify it.
  • The predicted neutrino flavor ratio from the decay chain (ν_e:ν_μ:ν_τ) differs from typical astrophysical sources; a future detection of a neutrino burst temporally coincident with the TeV beams could discriminate this model from hadronic re-acceleration models.

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

5 major / 5 minor

Summary. The paper proposes a mechanism for the 'disconnected' TeV gamma-ray beams observed by H.E.S.S., HAWC, and LHAASO at tens to hundreds of light-years from SS433. It argues that a past UV flare in the SS433 system converted a ~27.5 PeV proton jet into a ~25 PeV neutron jet through the Delta resonance (p+γ→Δ→n+π+). The neutrons would travel a long distance without radiating and then beta-decay, producing TeV electrons whose inverse-Compton emission appears as the far TeV beams. The manuscript gives a neutron decay length estimate (Eq. 2), a resonance photon energy estimate (Eqs. 3–5), a conversion optical depth estimate (Eqs. 9–10), and a qualitative discussion of Larmor radii and observational consequences.

Significance. The underlying idea is physically motivated and offers a way around the re-collimation problem of shock-reacceleration models: a neutral beam preserves collimation while propagating undeflected, and neutron decay naturally deposits energy at a distance set by the boosted lifetime. The paper also suggests testable searches (old photographic plates, other microquasars, IceCube neutrinos). However, the manuscript as written does not establish the claimed explanation. There is an order-of-magnitude arithmetic error in the central distance-energy relation, the resonance condition is not written correctly, the quoted optical depth is internally inconsistent, and no gamma-ray flux or spectrum is predicted for comparison with observations. If these issues are corrected and a quantitative flux estimate is added, the model could be a valuable alternative explanation.

major comments (5)
  1. [Section 4, Eq. (2)] The central flight-distance relation is off by a factor of 10. For E_n=25 PeV and neutron rest energy 0.94 GeV, γ=2.66e7, so L=βγcτ_n≈877γ light-seconds≈2.33e10 light-seconds≈7.4e2 ly, not 75 ly. To obtain 75 ly one needs γ≈2.7e6, i.e. E_n≈2.5 PeV. Thus Eq. (2) cannot be used to set the 25 PeV energy scale adopted throughout the paper.
  2. [Sections 4–6] The paper never derives a gamma-ray flux or spectrum. Even granting the hypothetical flare and efficient pγ→Δ→n conversion, the model stops after estimating the conversion probability; it does not compute the neutron luminosity from the flare, the electron injection spectrum from neutron β-decay, the inverse-Compton emission on ambient radiation fields (CMB, starlight, IR), or the resulting angular morphology. There is therefore no quantitative comparison with the H.E.S.S. or HAWC observations. For a claim that the TeV beams are explained, at least an order-of-magnitude flux prediction is required.
  3. [Section 4, Eqs. (3)–(5)] The Delta-resonance condition omits the proton mass. For p+γ→Δ with an isotropic photon field, m_Δ^2 = m_p^2 + 2E_pE_γ, so the required photon energy is (m_Δ^2−m_p^2)/(2E_p), a factor m_Δ^2/(m_Δ^2−m_p^2)≈2.4 smaller than Eq. (4). In addition, a blackbody at temperature T does not have photons of energy kT; the distribution peaks near 1.59kT and the mean photon energy is 2.70kT. The quoted T=3.2e5 K and L_flare therefore do not follow from the equations as written and need to be recomputed self-consistently.
  4. [Section 5, Eq. (10)] The numerical value 23.2 in Eq. (10) is not reproducible with the density stated in the text. With n_Th=3.9e12 cm^-3, σ_Δ=5e-28 cm^2, and D_j=R_sun=6.96e10 cm, the optical depth is τ≈1.4e-4, not 23.2. The value 23.2 corresponds to n_Th≈6.6e17 cm^-3, the (55.4)^3-scaled flare density. The same symbol n_Th is used for the solar photosphere density and the flare density; this ambiguity is load-bearing because the conversion probability is the heart of the model.
  5. [Section 4, Eqs. (1)–(5)] As presented, the model fits the observed distance rather than predicting it: E_n is chosen by inverting Eq. (2), and the flare temperature is tuned through Eqs. (4)–(5) to produce that neutron energy. Any observed distance could be accommodated by rescaling E_n and T. To make the claim testable, the authors should derive E_n from an assumed proton acceleration spectrum and flare photon spectrum, or provide an independent observable (flux, spectrum, time delay) predicted by the model.
minor comments (5)
  1. [Abstract] The abstract contains a stray string 'CV October 2025' in the sentence about proton collisions; this appears to be an editing artifact and should be removed.
  2. [Section 3, references] Reference [12] (Sudoh, Inoue, Khangulyan 2020) is cited for the LHAASO study of SS433, but the cited paper is a theoretical multiwavelength study, not a LHAASO observation. Please correct the citation or the associated text.
  3. [Section 4, Eq. (1)] The symbol 'ls' is used without definition; clarify that it denotes light-seconds and make the conversion to light-years explicit.
  4. [Abstract and Section 6] The statements 'well consistent with observations' and 'Alternative models appear uncompetitive' are not supported by any quantitative comparison in the manuscript. Please either add the comparison or soften these claims.
  5. [Section 6] The phrase 'around the end of War World' appears to be a typo; rephrase to identify the actual historical period.

Circularity Check

2 steps flagged

Observed 75 ly beam distance is inserted into Eq. (2) to fix 25 PeV; the paper later presents that same distance as the model's explanatory prediction, so the central match is by construction.

specific steps
  1. fitted input called prediction [Section 4, Eq. (2); Section 6 Conclusions]
    "L_n =75 (E_n/25PeV) ly ... This distance of 75 ly is the first disconnected TeV signature from SS433; its size could be twice as large, assuming double the UHE neutron energy. We first use it to set a scale for the model."

    The observed H.E.S.S./HAWC/LHAASO distance (75 ly) is the input that fixes the neutron energy scale (25 PeV) through the neutron-lifetime flight-distance formula. Later the paper states that a 25 PeV neutron jet 'possibly explain[s] the puzzling separated twin TeV gamma beam at 75 ly distance', using Eq. (2) again. Because no independent measurement of 25 PeV is provided, the distance claimed to be explained is the same number inserted in the normalization; the match is a restatement of the fit, not an independent prediction.

  2. other [Section 4, Eqs. (3)-(5)]
    "to guarantee a final 25PeV neutron energy one must assume a 10% additional primary energy leading to a tuned lower energy photon as follow: E_gamma = ... = 3.2 10^5 K * k_B (E_p/(27.5PeV))"

    The Delta-resonance condition is presented as independent physics, but the photon temperature 3.2e5 K is derived by requiring the resonance to yield a 25 PeV neutron, and 25 PeV itself was fixed by fitting the observed 75 ly distance in Eq. (2). The flare is not independently observed, so this 'tuned' temperature does not break the fitting loop: it is a consistency condition that inherits the fitted neutron energy, not an external constraint.

full rationale

The central circularity is in the distance-energy relation. Eq. (2) is used with the observed 75 ly to define E_n = 25 PeV; the same equation is then quoted to conclude that a 25 PeV neutron jet explains the 75 ly beam. Since E_n has no independent observational anchor, the claimed quantitative agreement at 75 ly is the fitted input re-expressed as an output. The Delta-resonance kinematics (Eqs. 3-5) do not rescue this: their 3.2e5 K flare temperature is tuned to the same fitted 25 PeV, and no such flare is observed. There is no significant self-citation circularity: the prior author papers [3,4] are used to state the model, but the derivation is in the text, and the GZK citations [13,14] are external. The absence of a flux/spectrum prediction is a serious correctness/evidentiary problem but is not itself a circularity. Overall, the one central quantitative prediction reduces by construction to its input, giving partial circularity (score 6).

Axiom & Free-Parameter Ledger

5 free parameters · 4 axioms · 0 invented entities

No new particles or entities are invented. The free parameters are concentrated in the flare scenario: the neutron energy is set by the observed distance, and the flare temperature/luminosity/disk size are inferred from that tuned energy. The model rests on an unobserved past flare, plus the standard Delta-resonance/neutron-decay/ICS chain. The central physical mechanism uses known physics, but the quantitative fit is the weak point.

free parameters (5)
  • Proton/neutron energy E_p = 27.5 PeV (E_n = 25 PeV) = 27.5 PeV / 25 PeV
    Chosen so that the neutron decay length L_n (Eq. 2) equals the observed 75 ly distance. Not independently measured; the paper then uses this scale to compute the photon temperature and flare properties.
  • Neutron energy for 150 ly spot = ~50 PeV
    Section 4 says 'its size could be twice as large, assuming double the UHE neutron energy.' Again chosen to match the second observed distance.
  • Flare blackbody temperature T = 3.2e5 K (E_gamma = 27.6 eV) = 3.2e5 K
    Derived from the assumed 27.5 PeV proton energy and the Delta resonance mass (Eq. 5); depends on the fitted energy scale.
  • Flare luminosity L = 3.57e40 erg/s = 3.57e40 erg/s
    From Stefan-Boltzmann using the above temperature and an assumed solar-sized radiating area (Eq. 7). Not based on an observed flare.
  • Accretion disk / flare size D_j = solar radius = R_sun
    Assumed 'as a first estimate' (Section 5); directly enters Eq. 10 (conversion probability). No observational basis given.
axioms (4)
  • ad hoc to paper SS433 had a nova-like flare ~75-150 years ago with UV temperature and luminosity as specified.
    The entire mechanism requires such a flare, but no evidence is provided. The paper admits it is a hypothesis and suggests checking old photo-plates (Section 6).
  • domain assumption PeV protons in the jet interact with thermal UV photons in the flare region through the Delta resonance.
    Standard physics (photo-pion production), but its applicability here depends on the unobserved flare and on protons being accelerated to ~28 PeV in SS433's jet (Section 4).
  • domain assumption The neutron beam remains collimated and suffers no significant energy losses or scattering over ~75 ly.
    Invoked implicitly in the model; neutrons are neutral so they are not deflected in magnetic fields, but the paper does not discuss neutron interactions with ambient matter/radiation over that path.
  • domain assumption The TeV gamma rays observed far away arise from inverse-Compton scattering of the beta-decay electrons on ambient photon fields.
    Standard radiation mechanism, but the paper does not compute the ambient photon density in W50. No flux calculation is provided (Sections 3 and 6).

pith-pipeline@v1.3.0-alltime-deepseek · 4539 in / 4981 out tokens · 93913 ms · 2026-08-03T17:59:36.060309+00:00 · methodology

0 comments
read the original abstract

The SS433 is a well-known binary system with an internal black hole, which is stripping mass from an orbiting companion of ten solar masses, at a hundred of light-seconds away. The black hole and its accretion disk fuel a thin precessing jet, whose spirals are well-observed. Surprisingly, disconnected gamma-ray tails have recently been discovered by H.E.S.S., HAWC and LHAASO, hundreds of light-years away and with energies of tens of TeV. We suggest that tens PeV neutron burst jets were ejected from the SS433 system over the past century. These beams of ultra high-energy PeVatron neutrons, by their in-flight beta decay and Inverse Compton scattering, could be the source of the enigmatic, distant and disconnected tens of TeV gamma-ray beams. These ultra-relativistic PeV neutron jets could have been formed during one of the system's rare and intense tidal eruptions, when tens of PeV protons collide CV October 2025 with thermal ultraviolet photons, creating delta resonances. Their decay into secondary neutron beams of tens of PeV is well consistent with observations. Alternative models appear uncompetitive.

Figures

Figures reproduced from arXiv: 2512.07012 by Daniele Fargion, Danila Sopin, Maxim Yu. Khlopov, Pier Giorgio De Sanctis Lucentini, Sara Turriziani.

Figure 1
Figure 1. Figure 1: Above an artist’s impression of the SS 433 system, showing the jets (blue) and the surrounding W50 (red): the jets travel undetected for a distance of about 75 ly before suddenly reappearing as bright sources of non-thermal emission (X-rays and gamma rays) as observed by H.E.S.S., HAWC and LHAASO inside the nebula long before generated by a supernova. Below [1] the image of the H.E.S.S. data with the addit… view at source ↗
Figure 2
Figure 2. Figure 2: A simplified description of the inner SS433 binary system, in an approximated size: an accretion disk on a BH and a companion star of comparable mass, both of them, with a nominal ten solar mass, in their corresponding Kepler circular distance. The star radius and its particular the accretion disk, as well as the nova-like flare size are approximated just for a comprehensive view, but they may be a little … 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

14 extracted references · 3 linked inside Pith

  1. [1]

    Collaboration*†, F

    H. Collaboration*†, F. Aharonian, F.A. Benkhali, J. Aschersleben, H. Ashkar, M. Backes et al.,Acceleration and transport of relativistic electrons in the jets of the microquasar ss 433,Science383(2024) 402

    2024

  2. [2]

    Alfaro, C

    R. Alfaro, C. Alvarez, J. Arteaga-Velázquez, D.A. Rojas, H.A. Solares, R. Babu et al., Spectral study of very-high-energy gamma rays from ss 433 with hawc,The Astrophysical Journal976(2024) 30

    2024

  3. [3]

    what comes beyond the standard models

    R.Bernabei,P.Belli,A.Bussolotti,V.Caracciolo,R.Cerulli,A.Leoncinietal.,Proceedings to the 27th workshop" what comes beyond the standard models" bled, july 8-17, 2024,arXiv preprint arXiv:2504.17803(2025)

    Pith/arXiv arXiv 2024

  4. [4]

    Fargion,SS433 Microquasar Jet and the TeV Resurgence beam,arXiv e-prints(2024) arXiv:2412.08011 [2412.08011]

    D. Fargion,SS433 Microquasar Jet and the TeV Resurgence beam,arXiv e-prints(2024) arXiv:2412.08011 [2412.08011]. 8 SS433 PeV jet into TeV far beamD. Fargion

    Pith/arXiv arXiv 2024

  5. [5]

    Fargion and A

    D. Fargion and A. Salis,Inverse compton scattering off black body radiation in high energy physics and gamma (mev–tev) astrophysics,Physics-Uspekhi41(1998) 823

    1998

  6. [6]

    Levan, A

    A.J. Levan, A. Martin-Carrillo, T. Laskar, R.A.J. Eyles-Ferris, A. Sneppen, M.E. Ravasio et al.,The day-long, repeating grb 250702bde / ep250702a: A unique extragalactic transient, 2025

    2025

  7. [7]

    Fargion and M

    D. Fargion and M. Grossi,Grbs, sgrs by uhe leptons showering, blazing and re-brightening by precessing gamma jets in-off axis,Chinese Journal of Astronomy and Astrophysics6 (2006) 342

    2006

  8. [8]

    Fargion, M

    D. Fargion, M. Khlopov and P. Oliva,Could GRB170817A be really correlated to an NS–NS merging?,Int. J. Mod. Phys. D27(2017) 1841001 [1710.05909]

    Pith/arXiv arXiv 2017

  9. [9]

    Fargion,Lightest to heavy uhecr nuclei in a local universe, inEPJ Web of Conferences, vol

    D. Fargion,Lightest to heavy uhecr nuclei in a local universe, inEPJ Web of Conferences, vol. 319, p. 07004, EDP Sciences, 2025

    2025

  10. [10]

    Collaboration*†, R

    T.A. Collaboration*†, R. Abbasi, M. Allen, R. Arimura, J. Belz, D. Bergman et al.,An extremelyenergeticcosmicrayobservedbyasurfacedetectorarray,Science382(2023)903

    2023

  11. [11]

    Fargion, P.G

    D. Fargion, P.G. De Sanctis Lucentini and M.Y. Khlopov,Uhecr clustering: Lightest nuclei from local sheet galaxies,Universe10(2024) 323

    2024

  12. [12]

    Sudoh, Y

    T. Sudoh, Y. Inoue and D. Khangulyan,Multiwavelength emission from galactic jets: the case of the microquasar ss433,The Astrophysical Journal889(2020) 146

    2020

  13. [13]

    Greisen,End to the cosmic-ray spectrum?,Physical Review Letters16(1966) 748

    K. Greisen,End to the cosmic-ray spectrum?,Physical Review Letters16(1966) 748

    1966

  14. [14]

    Zatsepin and V.A

    G.T. Zatsepin and V.A. Kuz’min,Upper Limit of the Spectrum of Cosmic Rays,Soviet Journal of Experimental and Theoretical Physics Letters4(1966) 78. 9

    1966