Axion-like particle constraints from preSN in future experiments

Federica Giacchino

REVIEW 4 major objections 4 minor 15 references

Axion-like particle constraints from preSN in future experiments

T0 review · 4 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash

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Pith's one-line read The paper claims that a pre-supernova red supergiant like Betelgeuse could be a discovery source for axion-like particles in the hard-X/MeV band, with the strongest projected reach coming from e-ASTROGAM, COSI, and GECCO.

desk verdict Reasonable forecast for ALP searches with future MeV telescopes, but the claimed discovery potential is under-supported by the background treatment. read the letter →

arxiv 2506.08610 v1 pith:2CYFGENS submitted 2025-06-10 hep-ph

Federica Giacchino This is my paper

classification hep-ph

keywords axion-likeparticlesALP-photonconversionBetelgeusepre-supernovaMeVgamma-rayastronomyComptontelescopesstellarevolutiondiscoverypotential

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 argues that a nearby pre-supernova red supergiant such as Betelgeuse could be the first astrophysical source from which axion-like particles are discovered rather than merely bounded. It builds the expected ALP flux from the three dominant production mechanisms in an advanced stellar core — Primakoff conversion, Compton scattering, and electron-nucleus Bremsstrahlung — using twelve stellar models of Betelgeuse that reach the neon-burning phase. The ALPs convert into photons in the Galactic magnetic field, and the paper projects that five planned or proposed MeV observatories (COMCUBE, GECCO, COSI, AMEGO-X, e-ASTROGAM) can detect or constrain that photon signal. For a benchmark mass $m_a = 3.5\times10^{-11}$ eV, the result is a discovery region with $g_{ae} < 2\times10^{-13}$ and $g_{a\gamma} < 8\times10^{-11}\,\mathrm{GeV}^{-1}$ for e-ASTROGAM, COSI, and GECCO. The paper's message is that the new MeV experiments can probe axion couplings in a mass range that current instruments cannot reach.

What carries the argument

The argument is carried by a three-part chain. First, an ALP production spectrum combines Primakoff, Compton, and Bremsstrahlung terms with coefficients and spectral indices taken from twelve stellar models of Betelgeuse computed with the Full Network Stellar Evolution code (FuNS). Second, the ALP-to-photon conversion probability in the Galactic magnetic field, in the regime where the product of momentum transfer and magnetic-field length satisfies $qd \ll 1$, is energy independent, so the detected photon spectrum keeps the shape of the emitted ALP spectrum. Third, the effective areas and energy bands of COMCUBE, GECCO, COSI, AMEGO-X, and e-ASTROGAM are folded with an assumed $B_T = 1.4\,\mu\mathrm{G}$ field over $d = 200$ pc to convert the expected flux into 95% confidence upper limits on $g_{ae}$ and $g_{a\gamma}$. The load-bearing numerical input is the stellar model labeled model 11, which gives the most promising signal.

What would settle it

Recompute the expected photon counts for a $5\times10^4$ second pointed observation of Betelgeuse with each experiment's full instrument response (effective area, energy dispersion, angular resolution, and particle background), instead of the simplified background flux used in the paper; if the background-only counts in the 100 keV to 10 MeV band match or exceed the predicted ALP signal, the claimed discovery region would not survive.

Watch

Extended reading notes

Core claim

The central discovery claim is that, at ALP mass $m_a = 3.5\times10^{-11}$ eV, a $5\times10^4$ second observation of Betelgeuse with e-ASTROGAM, COSI, or GECCO would enter a discovery region of the ($g_{ae}$, $g_{a\gamma}$) plane, namely $g_{ae} < 2\times10^{-13}$ and $g_{a\gamma} < 8\times10^{-11}\,\mathrm{GeV}^{-1}$ at 95% confidence. For lighter masses $m_a < 10^{-10}$ eV, GECCO and e-ASTROGAM probe the product $g_{a\gamma}\,g_{ae}$ in the range $(1\text{--}4)\times10^{-25}\,\mathrm{GeV}^{-1}$, and COSI covers $(3\text{--}4)\times10^{-25}\,\mathrm{GeV}^{-1}$; for $m_a > 10^{-10}$ eV, AMEGO-X and a 64-unit COMCUBE array add coverage. The paper presents this as a preliminary projection that fills the 'MeV gap' left by NuSTAR, whose sensitivity drops above 80 keV, and it identifies the neon-burning stellar model (model 11) as the most promising source stage.

Load-bearing premise

The projected limits depend on simulated backgrounds that omit how the detectors actually respond to photons, and the paper states this omission leads to an underestimation of the background; if realistic detector backgrounds are larger, the claimed discovery regions could shrink or disappear.

Editorial extensions

If this is right

A $5\times10^4$ second pointed observation of Betelgeuse by e-ASTROGAM, COSI, or GECCO could yield the first positive detection of axion-like particles, rather than an upper limit.
If no signal appears, the same observation would strengthen existing constraints on $g_{ae}$ and $g_{a\gamma}$ in the sub-neV mass region, complementing the earlier NuSTAR bound.
The same flux and conversion pipeline can be applied to the roughly twenty supergiants within one kiloparsec, increasing the odds of catching one in a late pre-supernova stage.
A detected continuum in the hard-X/MeV band would simultaneously test the stellar evolution models of Betelgeuse, since the predicted spectrum is tied to the neon-burning phase.
These results give concrete physics motivation for including ALP searches in the design of Compton-telescope missions aimed at the MeV gap.

Reading between the lines

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

A natural next step, beyond what the paper computes, is to redo the projections with full instrument response; realistically, the true discovery regions will be smaller, though not necessarily absent.
The conversion probability scales as $B_T^2$, so the assumed $1.4\,\mu\mathrm{G}$ transverse field over $200$ pc is a strong assumption; mapping the Galactic magnetic field along the line of sight could shift the projected limits by a factor of a few.
The same method could be applied to other late-stage red supergiants and to future instruments beyond the five considered here; a time-resolved campaign might even catch the signal changing as the star approaches core collapse.
A quantitative check is available before launch: use the public sensitivity tools of each mission to compute expected counts with and without the ALP signal, which would test whether the claimed discovery region is already excluded by known backgrounds.

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Editorial analysis

A structured set of objections, weighed in public.

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

Desk Editor's Note

read the letter

Short version: this is a conference proceedings that takes an existing Betelgeuse ALP flux calculation and applies it to five future MeV telescopes, with the claim of a discovery potential. The new piece is the forecast for the ASTROMEV instruments, and the author deserves credit for putting specific numbers on the table and for flagging that the background simulation excludes instrument response.

The paper does several things right. It identifies a real gap: NuSTAR's sensitivity drops above roughly 80 keV, and current MeV instruments cannot probe this kind of source. The choice of Betelgeuse as a pre-SN target is sensible, and the paper makes contact with the relevant literature (Xiao et al., Straniero et al., the ASTROMEV proposals). The author is also honest in Section 3: the instrumental response functions are not included in the simulation, which leads to an underestimation of the background. That admission is why the central claim is not properly supported.

The problem is that the discovery potential is built on 95% C.L. limits derived from those underestimates. For Compton telescopes, instrumental background (cosmic-ray interactions, activation, albedo) usually dominates the diffuse astrophysical flux, and energy dispersion and angular response affect both signal and background in each bin. The paper gives no quantitative estimate of the effect, does not show the derived exclusion contours, and gives no statistical detail. The text also has typos and lists COSI twice in the discovery-region sentence. These are fixable, but as it stands the reader cannot verify the central claim. The novelty is limited—the flux model and conversion formalism come from earlier work—but the application to these future instruments is new, and the suggestion that AMEGO-X and a 64-satellite COMCUBE array could reach unexplored couplings for m_a > 10^-10 eV is worth checking.

My take: this is a legitimate, preliminary forecast, not a finished analysis. I would send it to a referee if it were submitted as a full paper, with the expectation of substantial revision—notably, a proper simulation with instrument response, plots of the limits, and a corrected list of experiments. As a proceedings contribution it is fine for what it is, but I would not cite it in my own work until the sensitivity analysis is made transparent.

Who is it for: ALP phenomenologists and the collaborations building COSI, e-ASTROGAM, GECCO, AMEGO-X, and COMCUBE. They could use this as a starting point, but they should treat the projected discovery regions as upper bounds pending a more realistic background treatment.

Referee Report

4 major / 4 minor

Summary. This proceedings paper proposes a search for axion-like particles (ALPs) produced in the pre-supernova red supergiant Betelgeuse, using future MeV gamma-ray telescopes: COMCUBE, GECCO, COSI, AMEGO-X, and e-ASTROGAM. The ALP production spectrum is taken from stellar models of Betelgeuse (Ref. [6]), and the ALP-photon conversion probability is computed with a standard first-principles formula. The paper claims that for a benchmark with B_T = 1.4 μG, d = 200 pc, and n_e = 0.013, the future instruments can reach a discovery potential in the ALP parameter space, e.g., for m_a = 3.5e-11 eV the region g_ae < 2e-13 and g_ag < 8e-11 GeV^-1. The analysis uses FLUKA/MegaLib simulated backgrounds, but instrumental response functions are not included. The central claim is stated without showing the derived 95% C.L. limits or the statistical procedure.

Significance. If the projected discovery potential is robust, this paper would provide a concrete physics motivation for the proposed MeV missions and extend the Betelgeuse ALP search program beyond the NuSTAR sensitivity window. The use of publicly benchmarked stellar models and first-principles conversion formulas is a strength, and the focus on a specific, observationally motivated target is useful. However, the significance is currently limited by the absence of the actual projected limit curves and by the unquantified neglect of instrumental response functions, which the paper itself admits underestimates the background. The novelty is incremental relative to the existing NuSTAR-based analysis of Ref. [6], but the extension to future instruments is of community interest if the missing results are provided.

major comments (4)

[Section 3] The central claim—a 95% C.L. discovery potential for m_a = 3.5e-11 eV with g_ae < 2e-13 and g_ag < 8e-11 GeV^-1—is stated without showing the corresponding upper-limit or discovery contours, and no statistical procedure (binning, likelihood, background treatment, systematic uncertainties) is described. The reader cannot verify how the 95% C.L. limits are derived from the simulated backgrounds or how the quoted coupling ranges are obtained. Please add the projected exclusion/discovery plots and a complete description of the statistical method.
[Section 3, background simulation] The manuscript states that instrumental response functions are not included and that this 'leads to an underestimation of the background,' but it does not quantify the size of the effect. For MeV Compton telescopes, energy dispersion and angular response change both signal and background counts per bin, and instrumental backgrounds from activation and albedo often dominate the astrophysical diffuse flux. Without a quantitative estimate or a conservative treatment, the quoted discovery region may be overly optimistic; please provide a robustness check or a reliable assessment of this effect.
[Section 2, Eq. (1)] The parameters C_P, C_C, C_B, β_P, β_C, β_B, and the reference energies E0^P, E0^C, E0^B are taken from Table 1 of Ref. [6], but the text does not give the adopted values for model 11 or justify why model 11 is called 'the most promising stellar model.' The sensitivity of the claimed discovery region to the stellar-model choice is therefore not assessed. Please state the adopted parameter values and discuss the model dependence.
[Section 3] The sentence listing instruments for the discovery region, 'for e-ASTROGAM, COSI, GECCO and COSI,' lists COSI twice and omits AMEGO-X; this typo obscures which instruments are actually claimed to cover the region. Also, the column labels of Table 1 are insufficiently defined (e.g., 'En' is not explained), and the observation time, energy binning, and exposure assumptions behind the quoted limits are not given.

minor comments (4)

[Abstract and Section 2] The abstract contains 'Primako?' which should be 'Primakoff'; the author affiliation contains 'Italty' instead of 'Italy'; and 'Red Supergiant Star (RGS)' should be 'Red Supergiant (RSG)' for consistency with standard notation.
[Section 3] The phrase 'Using 50×10^3 seconds observation of Betelgeuse by the previous satellite telescopes' is ambiguous: it should specify whether this is the exposure assumed for each future experiment and whether it is a realistic assumption for all listed missions.
[Section 3] The acronym 'ASTROMEV' is used without definition; please define it at first use as a collective label for the proposed MeV missions.
[References] Reference [7] has incomplete page information ('105?108' instead of '105–108') and would benefit from a DOI or arXiv identifier; other references are fine.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the ALP spectrum, conversion probability, and experimental sensitivities are imported from independent external work and standard formulas, with no fitted parameter renamed as a prediction.

full rationale

The paper's derivation chain is: stellar-model spectra from the FuNS code via Refs. [5] and [6] feed the analytic ALP production rate (Eq. 1); the ALP-photon conversion probability (Eq. 2) is the standard mixing formula with stated benchmark values (B_T = 1.4 uG, d = 200 pc, n_e = 0.013); and the experimental sensitivities are taken from the cited instrument papers (COMCUBE [7], GECCO [8], COSI [9], AMEGO-X [10], e-ASTROGAM [11]). The claimed discovery regions are derived from these external inputs by the usual 95% C.L. counting procedure; no parameter is fitted to the claimed result, and no load-bearing self-citation appears (the author cites no prior work of their own). The stated limitation in Section 3 that "The instrumental response functions of the experiments are not included in the simulation, which leads to an underestimation of the background" is a genuine robustness concern about the projected discovery potential, as is the absence of the derived limit curves and statistical details, but neither constitutes circularity: the inputs are not defined in terms of the output, and the conclusion is not forced by construction. The appropriate circularity score is therefore 0.

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

The paper introduces no new physics and no new parameters beyond imported benchmark values. Its main quantitative conclusions depend on assumed inputs from prior stellar models and on simplified background simulations, which are not validated in this text.

free parameters (3)

Benchmark values for Betelgeuse (B_T, distance, electron density) = B_T = 1.4 microG, d = 200 pc, n_e = 0.013 cm^-3
Chosen by hand as benchmark for the conversion probability and flux; taken from [6] but adopted here without uncertainty analysis.
Stellar model choice = Model 11 among 12 FuNS models
The paper selects model 11 as the most promising for detection, without showing how constraints vary across the other 11 models.
Observation time = 50,000 s
Adopted as representative exposure for the 95% C.L. limits, matching earlier NuSTAR observations, with no scaling study.

assumptions (3)

domain assumption ALP production spectrum in Betelgeuse is described by Eq. (1) with parameters from the FuNS stellar models in [6].
The paper imports this spectrum wholesale from prior work and selects model 11, so the central flux depends on that external modeling.
domain assumption ALP-photon conversion in the Galactic magnetic field is energy-independent with qd << 1, using uniform B_T = 1.4 microG and n_e = 0.013 cm^-3.
Eq. (2) is used with benchmarks chosen without validating them for the actual line of sight to Betelgeuse.
ad hoc to paper Simulated backgrounds from FLUKA/MegaLib, without instrument response functions, are a reliable basis for 95% C.L. limits.
This is an ad hoc assumption to the paper because the author explicitly states the response functions are excluded, understating the background.

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Cite this review

Pith. "Pith review of Axion-like particle constraints from preSN in future experiments." pith.science (2026). https://pith.science/paper/2CYFGENS

@misc{pith2026250608610,
  author       = {Pith},
  title        = {Pith review of: Axion-like particle constraints from preSN in future experiments},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/2CYFGENS}},
  note         = {Machine review of arXiv:2506.08610}
}

read the original abstract

We extend the study of the search for ALP-photon emissions from a Supernovae (SNe) progenitor, the Red Supergiant Star (RGS), as Betelgeuse, arising through a combination of Bremsstrahlung, Compton, and Primako? processes, in the hard-X and MeV energy range, using the next proposed and future experiments, such as COMCUBE, GECCO, COSI, AMEGO-X, and e-ASTROGAM.

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Works this paper leans on

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Pith tools

Reviewed August 7, 2026 · model on record in the stance chip above.

[1] [6]

G. G. Raffelt, Lect. Notes Phys. 741, 51-71 (2008) doi:10.1007/978-3-540-73518-2\_3 [arXiv:hep-ph/0611350 [hep-ph]]

arXiv 2008

[2] [1]

R. D. Peccei and H. R. Quinn, Phys. Rev. Lett. 38, 1440-1443 (1977) doi:10.1103/PhysRevLett.38.1440

doi:10.1103/physrevlett.38.1440 1977

[3] [2]

G. B. Gelmini and M. Roncadelli,

work page

[4] [3]

I. G. Irastorza and J. Redondo,

work page

[5] [4]

Di Luzio, M

L. Di Luzio, M. Giannotti, E. Nardi and L. Visinelli, Phys. Rept. 870, 1-117 (2020) doi:10.1016/j.physrep.2020.06.002 [arXiv:2003.01100 [hep-ph]]

arXiv 2020

[6] [5]

Caputo and G

A. Caputo and G. Raffelt, PoS COSMICWISPers, 041 (2024) doi:10.22323/1.454.0041 [arXiv:2401.13728 [hep-ph]]

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doi:10.3847/1538-4357/ac4f5f

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work page Pith review arXiv 2019