{"id":"88a5e715-e958-44a9-99fe-e9909011f32a","arxiv_id":"1908.02171","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Cosmic rays can be accelerated to energies above 100 TeV as early as a few hours after the shock breakout of a core-collapse supernova in a red supergiant.","lead":"This paper simulates the explosion of a red supergiant star and asks when the blast wave can start accelerating cosmic rays. It finds that the shock becomes able to accelerate particles within about an hour of shock breakout, and that cosmic rays can reach hundreds of teraelectronvolts within the first day.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Equal electron-proton temperature closure shortens the Coulomb-loss delay that sets the claimed onset; the timing result needs a sensitivity check.","rationale":"The reader's weakest assumption is the one I find most load-bearing. The Emax plateau comes from Bell-instability estimates and is not very sensitive to electron heating; however, the claim that CRs exceed 100 TeV '~1 hour after onset' inherits the onset condition directly. The equal-T closure maximizes the simulated electron temperature and therefore minimizes Coulomb losses. The paper itself plots tau_Coul,0 as a limiting case but never states the resulting shifted onset, leaving an unquantified sensitivity in the central timing claim. I agree with the reader's conditional verdict; the missing sensitivity study and code details prevent full endorsement, but the science is plausible and the objection can be settled by a modest recomputation. I therefore recommend no change to the verdict.","tokens_in":6758,"tokens_out":15322,"duration_ms":189635,"concrete_test":"From the published Fig. 3 curves, find the time at which the red tau_acc,1GeV curve first drops below the dashed orange tau_Coul,0 curve (the zero-electron-temperature lower limit) rather than below the solid orange tau_Coul,Te,u curve. If this zero-temperature onset time is more than about 3 h after CS formation, or if it lies beyond the plotted first day, then the equal-temperature assumption is load-bearing for the headline. This check uses only data already shown and requires no code access.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's headline timing — CRs reaching >100 TeV about 1 h after the onset of acceleration and a few hours after shock breakout (Section 3 and Fig. 4) — is set by the condition that tau_acc,1GeV first falls below tau_Coul, the Coulomb loss time. In the simulation, tau_Coul is evaluated using the code's two-temperature closure in which electron and proton temperatures are taken equal (Section 2). A collisionless shock is not generally expected to heat electrons to the full proton temperature; if T_e is lower, the Coulomb loss time is shorter, and the intersection with the falling tau_acc,1GeV curve moves to later times. The authors display this sensitivity as the zero-temperature limiting curve tau_Coul,0 in Fig. 3 but do not report where tau_acc,1GeV crosses it. Because the electron temperature in the simulation is an upper limit rather than a conservative choice, the quoted ~1 h delay between CS formation and the start of acceleration is an optimistic value. This matters because the plateau Emax is largely insensitive to T_e, but the abstract's 'only a few hours after shock breakout' is precisely a timing statement.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents one-dimensional CR-radiation-hydrodynamics simulations of a red supergiant core-collapse supernova during the first day after core collapse. Starting from a 3D CO5BOLD progenitor density profile, the authors deposit 10^51 erg at the center and follow the shock until it becomes collisionless. They then compute the acceleration time to 1 GeV, the Coulomb, pp, adiabatic, and p-gamma loss times, and the maximum CR energy Emax using the Bell instability, assuming Bohm diffusion and a 1 mG initial magnetic field. The central quantitative claims are that CR acceleration starts roughly one hour after the formation of the collisionless shock and that Emax exceeds 100 TeV about one hour after the onset of acceleration, plateauing at a few hundred TeV by the end of the first day. The paper also explores how the three-dimensional structure of the progenitor affects the results by repeating the calculation along six different radial directions.","tokens_in":6939,"tokens_out":5453,"duration_ms":59638,"significance":"If the timing claim holds, this paper establishes that core-collapse supernovae exploding in dense winds become very-high-energy cosmic-ray accelerators within hours of shock breakout, with direct implications for TeV-PeV neutrino and gamma-ray searches during the first day after core collapse. The work combines a realistic 3D progenitor model with explicit CR pressure in the hydrodynamics and a Bell-instability-based calculation of Emax, and it shows that the plateau value of Emax is insensitive to the uncertain onset time. The direction-dependent analysis and the explicit caveat that a full 3D simulation is needed for a watertight estimate of the spread in breakout times are appropriate and honest. The main unresolved issue is not the eventual Emax but the delay before acceleration starts, because that delay controls the headline 'only a few hours after shock breakout' statement.","major_comments":[{"comment":"The code description states that 'electron and proton temperatures are assumed to be equal.' This maximizes the post-shock electron temperature and therefore maximizes the Coulomb loss time, making the onset of acceleration as early as possible. The paper's central timing claim—that acceleration starts only about one hour after CS formation and reaches >100 TeV 'only a few hours after shock breakout'—depends on this choice. The authors show the zero-temperature limiting curve tau_Coul,0 in Fig. 3 but do not report where tau_acc,1GeV crosses it. I request that crossing time, plus an intermediate case (for example Te = 0.1 Tp, which is more representative of weak or oblique collisionless shocks), and a revised timing statement if the zero-temperature intersection is significantly later. This is a sensitivity check for the headline quantitative result, not a circularity concern.","section":"Section 2 and Fig. 3"},{"comment":"The onset time is inversely proportional to the initial magnetic field strength through tau_acc,1GeV, and the paper adopts B = 1 mG without a sensitivity scan. The text notes that stronger fields accelerate particles faster, but the abstract's 'only a few hours' is a timing statement whose robustness to a weaker field is not demonstrated. Please show the intersection time for at least one lower and one higher magnetic field value, or explicitly state that the timing claim is conditional on B being close to 1 mG.","section":"Section 2, magnetic field parameter"},{"comment":"The quantitative Emax calculation and the implementation of CR pressure are delegated to Ref. [12], which is listed as 'in preparation.' As a result, the core derivation of the central result cannot be checked from the present manuscript. Please include the essential equations (for example the Bell-instability growth rate, the CR current, and the condition determining Emax) either in an appendix or by making the companion paper available, so that the scaling of Emax with time and density is verifiable.","section":"Section 2 and Ref. [12]"}],"minor_comments":[{"comment":"The word 'afer' in 'typically ∼ 1 hour afer the onset' should be 'after.'","section":"Section 3, text after Fig. 4"},{"comment":"The phrase 'two-temperature, i.e. electron and proton temperatures are assumed to be equal' is self-contradictory; if Te = Tp, there is only one temperature. Please describe the closure as a single-temperature or equilibrated-temperature approximation.","section":"Section 2, first paragraph"},{"comment":"The dashed orange curve tau_Coul,0 is discussed in the text but not defined in the caption. Please define all curves in the caption or refer explicitly to the text definitions so the figure is self-contained.","section":"Fig. 3 caption"},{"comment":"The abstract says 'only a few hours after shock breakout' while the detailed result in Section 3 is about one hour after the onset of acceleration, with the CS forming near 39000 s after core collapse. Please align these phrasings to make the quoted time relative to breakout versus relative to CS formation unambiguous.","section":"Abstract and Section 3"},{"comment":"The line keys in the right panel are small and the difference between the solid red tau_acc,Emax and dashed red tau_acc,1TeV curves is central to the argument; consider larger fonts or explicit curve labels.","section":"Fig. 3, right panel"}],"recommendation":"major_revision","confidential_remarks":"This is a proceedings contribution, and the main missing element is a sensitivity analysis of the timing claim with respect to Te and B, together with access to the unpublished companion paper Ref. [12]. The requested checks are feasible within the scope of the manuscript and would either strengthen the claim or require a more cautious wording. I do not see a circularity problem: the simulation is forward and no parameter is fitted to the Emax output. The self-citation to Ref. [2] is appropriate because the authors use that method. The paper would be suitable for acceptance after the timing sensitivity is quantified."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Short version: this is a proceedings paper, but the application is genuinely new. It takes the authors' existing CR-radiation-hydrodynamics machinery and drives it with a realistic, non-spherical red supergiant density profile from CO5BOLD, then computes when a collisionless shock can start accelerating cosmic rays and what Emax does during the first day. The directional study—six sightlines through the clumpy progenitor—is a real step beyond spherical models, and the conclusion that Emax plateaus at a few hundred TeV is clearly presented and carefully hedged.\n\nWhat the paper does well: the writing is clear, the limitations of 1D spherical simulation are acknowledged (including the warning that a 3D simulation would be needed for a watertight spread in breakout times), and the plateau energy is not very sensitive to the electron-temperature assumption. The calculation is forward, not fitted: shock evolution comes from the hydro simulation, and Emax comes from the Bell-instability model. The self-citations are fine; the missing piece is that the methods live in Ref. [12], 'in preparation,' so a referee cannot check the central calculation from this text.\n\nThe real soft spot is the timing claim. 'Only a few hours after shock breakout' is set by when Coulomb losses cease to suppress acceleration, and that crossover depends on the electron temperature. The code assumes Te = Tp behind the shock. That is an upper limit on electron heating, not a conservative choice; in oblique or weak collisionless shocks electrons are often cooler, so the Coulomb loss time would be shorter and the onset delayed. The authors plot the zero-temperature Coulomb loss curve in Fig. 3 but do not report where the acceleration time crosses it, which is exactly the sensitivity check the abstract needs. The same caveat applies to the 1 mG initial field: stronger fields make acceleration faster, but no error bars or parameter scans are given. None of this kills the energy-scale result, but it means the 'hours' in the abstract is optimistic.\n\nRecommendation: This deserves a serious referee, but not in this form. If it were submitted as a journal paper, I would send it out and ask for the methods appendix or code release, plus a sensitivity study on Te and magnetic field. As it stands, read it as a useful, plausible proceedings paper whose timing should be quoted with the equal-temperature caveat attached.","headline":"Realistic RSG density profiles push Emax to a few hundred TeV within the first day, but the headline timing rests on an optimistic Te=Tp assumption and methods parked in an unpublished reference.","tokens_in":7500,"tokens_out":2918,"would_cite":true,"duration_ms":34307,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"A core-collapse supernova in a red supergiant may accelerate cosmic rays past 100 TeV within hours of shock breakout.","keywords":["core-collapse supernovae","cosmic-ray acceleration","shock breakout","collisionless shocks","red supergiant progenitors","maximum cosmic-ray energy","diffusive shock acceleration","radiation-hydrodynamics simulations"],"falsifier":"Recompute the onset time with the same shock profiles but with electrons heated to a small fraction of the proton temperature, for example one tenth of it, as is typical of weak or oblique collisionless shocks, and check whether the 1 GeV acceleration time still drops below the Coulomb loss time within an hour of the collisionless shock forming. If it does not, the 'above 100 TeV within hours' result is an artefact of the electron-heating assumption. A complementary observational check is X-ray spectroscopy of a nearby Type II supernova within its first day: an electron temperature far below tens of keV would indicate stronger Coulomb losses than the simulation assumes.","tokens_in":6540,"feed_emoji":"💥","tokens_out":7005,"duration_ms":72209,"temperature":0.7,"pith_summary":"Core-collapse supernovae exploding inside the dense winds of red supergiants have long been considered possible cosmic-ray accelerators over decades, and this paper asks whether the very first day already works. The authors simulate the explosion with a radiation-hydrodynamics code that includes cosmic-ray pressure, starting from a realistic three-dimensional convective red-supergiant structure, and find that a collisionless shock forms within about an hour of shock breakout. They then show that Coulomb losses delay the start of acceleration by only roughly one hour, and that the maximum proton energy rises above 100 TeV about an hour after acceleration begins, plateauing at a few hundred TeV by the end of the first day. If this is right, a freshly exploded core-collapse supernova is a very-high-energy particle accelerator almost immediately, and should be observable in TeV and PeV neutrinos and gamma rays during its first day.","feed_headline":"Red-supergiant supernovae may make 100 TeV cosmic rays within hours","feed_subtitle":"A simulation shows the shock turns on about an hour after breakout, fast enough for TeV-scale acceleration on day one.","key_machinery":"The argument is carried by a one-dimensional CR-radiation-hydrodynamics simulation that uses the spherically averaged density and temperature profiles of a three-dimensional convective red supergiant as input. The simulation follows the radiation-mediated shock through the star, identifies the moment a collisionless shock forms after the radiation flash of shock breakout, and adds cosmic-ray pressure to the fluid. At each time it compares the Bohm-diffusion acceleration time to 1 GeV with the Coulomb, pp-collision, and adiabatic loss times to decide when acceleration can start, then computes $E_{\\max}$ from the current of escaping cosmic rays and the growth rate of the cosmic-ray-current-driven magnetic-field instability, checking the acceleration time to $E_{\\max}$ against pp, p$\\gamma$, and adiabatic losses.","core_discovery":"The paper's central claim is that the first day of a Type II supernova from a red supergiant already contains a working cosmic-ray accelerator. After shock breakout, a collisionless shock forms at $t \\simeq 39000$ s, and the acceleration time to 1 GeV drops below the Coulomb loss time at $t \\simeq 42000$ s, so particle acceleration starts only about an hour after the collisionless shock forms, for a 1 mG circumstellar magnetic field. From that onset, the maximum cosmic-ray energy $E_{\\max}$ reaches $\\geq 100$ TeV within roughly one hour and plateaus to a few hundred TeV by the end of the first day. The paper also finds that the limiting energy is set by the density of the circumstellar medium: in denser directions around the asymmetric progenitor, the plateau value of $E_{\\max}$ is a few times higher, although all directions agree to order of magnitude.","pith_inferences":["The two-temperature assumption likely makes the quoted onset time an optimistic lower bound: if collisionless heating leaves electrons cooler than protons, Coulomb losses are stronger and the '100 TeV within hours' result would shift to later times, possibly beyond the first day.","A natural extension is to rerun the same simulation with a separate electron temperature or a measured electron-heating prescription; the predicted spread in onset time would directly test how robust the early-emission window is.","If the prompt high-energy phase is real, a Galactic core-collapse supernova would produce a neutrino and gamma-ray flash within about an hour of shock breakout, giving wide-field instruments a sharp, testable time profile that distinguishes this model from later remnant emission.","A full three-dimensional CR-radiation-hydrodynamics run would be needed to know whether the spread in breakout times from clumpy structure is larger than the one-dimensional directional estimates; if clumps divert the shock, some lines of sight could lag much longer."],"forward_implications":["If the first day is already a cosmic-ray accelerator, core-collapse supernovae in dense winds are plausible sources of TeV and PeV neutrinos and gamma rays within hours of shock breakout, not only decades later as remnants.","The maximum cosmic-ray energy plateau by the end of day one is set by circumstellar density, so red supergiants with denser winds should produce the highest very-high-energy emission in their earliest phases.","Because Coulomb losses delay acceleration by only about an hour, searches for prompt high-energy emission from nearby supernovae should begin observing immediately after discovery rather than waiting for the remnant stage.","The direction-dependent onset times in the asymmetric progenitor mean that part of the shock is already accelerating particles while other parts are not, so high-energy emission may be modulated as the shock encounters different clumps."],"supporting_citations":[{"why":"Supplies the model for $E_{\\max}$ at the forward shock, based on the escape current of the highest-energy cosmic rays driving magnetic-field growth, including the density dependence used in Fig. 4.","marker":"[2]"},{"why":"Provides the shock-breakout photon flash that accelerates the circumstellar wind, which is the precondition for the later collisionless shock.","marker":"[5]"},{"why":"Gives the Compton cooling and bremsstrahlung energy-exchange formulae between fluid and radiation used in the simulation.","marker":"[6]"},{"why":"Supplies the three-dimensional radiative-hydrodynamics stellar convection code used to generate the realistic red supergiant density structure.","marker":"[7]"},{"why":"Provides the fundamental stellar parameters and the density and temperature profiles of the red supergiant simulation used as initial conditions.","marker":"[10]"},{"why":"Provides the method for determining the formation time of the collisionless shock and the radiation-hydrodynamics code into which cosmic-ray pressure is added.","marker":"[11]"},{"why":"Grounds the magnetic-field amplification mechanism at the shock that sets the energy scale of the accelerated cosmic rays.","marker":"[13]"}],"fun_headline_variants":["First-day supernova shock accelerates cosmic rays to 100 TeV","Supernova cosmic-ray accelerator turns on within an hour","100 TeV cosmic rays from red-supergiant supernovae in a day","Day-one supernova shock boosts cosmic rays past 100 TeV","Red supergiant supernova makes 100 TeV cosmic rays in a day"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The simulation assumes electrons and protons have the same temperature behind the shock, which maximises the electron temperature, weakens Coulomb losses, and therefore makes cosmic-ray acceleration start as early as possible.","fun_headline_variants_meta":{"raw":{"variants":["First-day supernova shock accelerates cosmic rays to 100 TeV","Supernova cosmic-ray accelerator turns on within an hour","100 TeV cosmic rays from red-supergiant supernovae in a day","Day-one supernova shock boosts cosmic rays past 100 TeV","Red supergiant supernova makes 100 TeV cosmic rays in a day"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000913,"raw_usage":{"total_tokens":3863,"prompt_tokens":830,"completion_tokens":3033,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":446,"completion_tokens_details":{"reasoning_tokens":2938}},"tokens_in":446,"tokens_out":3033,"duration_ms":21469,"temperature":1.0,"reasoning_tokens":2938,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T14:52:36.842356+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Recompute the onset time with the same shock profiles but with electrons heated to a small fraction of the proton temperature, for example one tenth of it, as is typical of weak or oblique collisionless shocks, and check whether the 1 GeV acceleration time still drops below the Coulomb loss time within an hour of the collisionless shock forming. If it does not, the 'above 100 TeV within hours' result is an artefact of the electron-heating assumption. A complementary observational check is X-ray spectroscopy of a nearby Type II supernova within its first day: an electron temperature far below tens of keV would indicate stronger Coulomb losses than the simulation assumes.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the shock-breakout photon flash that accelerates the circumstellar wind, which is the precondition for the later collisionless shock."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives the Compton cooling and bremsstrahlung energy-exchange formulae between fluid and radiation used in the simulation."},{"cited_title":"Collisionless Shocks and TeV Neutrinos before Supernova Shock Breakout from an Optically Thick Wind","cited_arxiv_id":"1503.04170","evidence_quote":"Provides the method for determining the formation time of the collisionless shock and the radiation-hydrodynamics code into which cosmic-ray pressure is added."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Grounds the magnetic-field amplification mechanism at the shock that sets the energy scale of the accelerated cosmic rays."}],"review_version":1}