{"id":"844cec9e-3349-4e5a-8ee6-12e540ddaf84","arxiv_id":"1909.00078","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":2,"one_line_summary":"No significant neutrino signal from fast radio bursts was found; IceCube sets the first MeV limits and the tightest GeV-to-TeV limits to date.","lead":"IceCube found no neutrinos arriving from fast radio bursts in either high-energy track events or low-energy ambient hit rates, and set the first limits on MeV neutrino emission from these bursts. The limits tighten previous constraints and show how future radio telescopes will improve the search.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"MeV limits are quoted for a single fiducial CCSN spectrum; without quantifying spectral dependence, the 'first limit on MeV neutrino emission' claim is overbroad.","rationale":"The reader's weakest assumption is exactly the spectral dependence of the MeV limits. This is the most load-bearing concern because the paper's headline includes a quantitative 'first limit on MeV neutrino emission from FRBs,' and that number is meaningful only under an assumed spectrum. The paper acknowledges the dependence but does not quantify it, leaving the central claim conditional. Other concerns (uncorrected trials in the MeV search, lack of systematic uncertainties) are secondary because they do not change the null result or the order-of-magnitude nature of the limits. The proposed test would settle whether the spectral choice actually changes the limits enough to undermine the wording of the claim. Since the reader already conditioned the verdict on this issue, my stress-test does not move the verdict.","tokens_in":5628,"tokens_out":4679,"duration_ms":43970,"concrete_test":"Recompute the 90% CL upper limits from the SNDAQ search (or a validated surrogate using the same off-time data and likelihood) for a grid of Fermi-Dirac spectra with mean energies 5, 10, 20, 30 MeV and pinching parameters alpha = 2, 3, 4, using the same DOM efficiencies and time windows. If the resulting fluence limits vary by less than a factor of ~2 across the grid, the spectral assumption is not the dominant systematic; if they vary by an order of magnitude or more, the paper's abstract and conclusion must be revised to state the limits are for the fiducial CCSN-like spectrum only.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim of the MeV component is an upper limit on neutrino fluence from FRBs. That limit is derived using the SNDAQ collective hit-rate excess, assuming a fiducial core-collapse supernova neutrino spectrum with mean energy 15.6 MeV and pinching parameter alpha=3 (Sec. 3). The conversion from an observed hit-rate excess to a fluence limit depends strongly on the incident neutrino spectrum: the dominant detection channel (inverse beta decay) has an energy-dependent cross section and Cherenkov yield, so the detector's response is not flat in neutrino energy. The paper explicitly notes 'there is dependency on the signal hit rate from varying incident fluxes [15]' but does not quantify this dependence. If a harder or softer spectrum changes the expected hit rate per unit fluence by an order of magnitude, then the quoted limits are not general limits on 'MeV neutrino emission' but specifically on emission with a CCSN-like spectrum. Since no FRB neutrino spectrum model exists, this is the least secure link in the chain from the data to the headline claim. The null result itself (no excess) is robust, but the quantitative 'first limit' is model-dependent.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This manuscript, an IceCube Collaboration contribution to ICRC 2019, describes two complementary searches for neutrinos from fast radio bursts (FRBs). The first is an unbinned maximum-likelihood muon-track search applied to 28 FRBs, using a looser event selection than the prior six-year analysis and testing both a stacking hypothesis and a max-burst hypothesis over a range of time windows. No significant excess is found, with post-trial p-values of 0.35 (stacking) and 0.33 (max-burst), and 90% confidence upper limits are placed on the time-integrated neutrino flux per FRB for E^-2 and E^-3 spectra. The second search uses the SNDAQ hit-rate stream to look for collective MeV-scale neutrino bursts from 21 FRBs over eight time windows; again no significant signal is found, and the authors report 90% upper limits on anti-electron-neutrino fluence assuming a fiducial core-collapse supernova spectrum. The paper closes with projections for future searches using next-generation radio interferometers.","tokens_in":5834,"tokens_out":4673,"duration_ms":44838,"significance":"If the results stand, the paper provides the most stringent limits to date on high-energy neutrino emission from FRBs and, for the first time, places limits on MeV-scale neutrino emission from FRBs. The high-energy analysis is methodologically sound: the likelihood is standard, the background is parameterized from data, and the post-trial p-values are obtained from Monte Carlo simulations. The reported null result is robust and does not depend on the assumed spectral shape of any hypothetical FRB neutrino emission. The paper also gives credit to the improvement over the six-year analysis, noting factor-of-50 stronger limits for short timescales under an E^-3 spectrum. The MeV component is a novel use of IceCube's supernova trigger, and the explicit use of an external CCSN spectral model (rather than a fitted model) keeps the circularity burden low. The main weakness is the unquantified spectral dependence of the MeV fluence limits, which affects the generality of the abstract's 'first limit on MeV neutrino emission' claim.","major_comments":[{"comment":"The quoted upper limits on anti-electron-neutrino fluence from FRBs are derived for a single fiducial core-collapse supernova spectrum with mean energy 15.6 MeV and pinching parameter alpha=3. The manuscript itself notes that the signal hit rate depends on the incident flux, but the size of this spectral dependence is not quantified. Because the MeV detection channel combines the inverse-beta-decay cross section, Cherenkov yield, and DOM threshold, the conversion from a hit-rate excess to a fluence limit can vary strongly with the assumed neutrino spectrum. As written, the abstract's claim of 'the first limit on MeV neutrino emission from FRBs' overstates the generality of the result. Please either (i) state in the abstract and conclusions that the limits apply specifically to a CCSN-like spectrum and quantify, even roughly, the expected variation with spectral shape, or (ii) rephrase the claim as a limit on the fiducial model.","section":"Section 3, MeV search and Figure 6"}],"minor_comments":[{"comment":"There is a typo in the text: 'backgrond' should be 'background'.","section":"Section 2.2"},{"comment":"The quantity sigma_i is introduced as the standard deviation of the hit rate in DOM_i, but the likelihood uses <sigma_i> in the denominator; please clarify whether <sigma_i> is the time-averaged standard deviation and how it is estimated.","section":"Section 2.2, Eq. (2.2)"},{"comment":"Unlike the high-energy limits in Figure 4, the MeV limits in Figure 6 are shown without any systematic uncertainty bands; a brief statement on the dominant systematics (e.g., DOM efficiencies, atmospheric muon rate modeling) would help the reader judge the robustness of the limits.","section":"Section 3, Figure 6"},{"comment":"The MeV search tests 21 FRBs across 8 time windows, but the reported significance is compared to a 3-sigma threshold from off-time windows without an explicit trials correction for the number of FRBs and time windows. The null result is unaffected because the largest observed significance is 2.55 sigma, but the procedure should be described more carefully to avoid an overclaim in future applications.","section":"Section 2.2, MeV search"},{"comment":"The claim that the high-energy limits are 'the most constraining' is supported by comparison with the preceding IceCube six-year analysis and by the effective-area comparison with ANTARES, but a direct limit-to-limit comparison with ANTARES is not shown; please state the basis of the comparison more explicitly.","section":"Abstract and Section 3"}],"recommendation":"minor_revision","confidential_remarks":"This is an ICRC proceedings paper, so the level of detail is appropriate for the venue. The null result is robust and the statistical methods are standard. The only substantive issue is the unquantified spectral model dependence of the MeV limits, which is a presentational/qualification matter rather than a fundamental flaw. I do not see circularity in the use of the prior IceCube analyses [13,14]. The requested revisions are local and do not require new analysis, though a rough quantification of the spectral dependence would strengthen the paper."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nThis is a straightforward, competent null-result paper from IceCube. The one thing you should know: it finds no neutrino excess coincident with FRBs, and in doing so it publishes the first MeV limits from FRBs and tighter GeV-TeV limits than the earlier six-year analysis. The novelty is real but modest — established methods applied to a young source class.\n\nWhat the paper does well: the high-energy search uses a loosened track selection than the six-year analysis, which buys effective area in the southern sky and at lower energies; the likelihood is standard, and they compute post-trial p-values from Monte Carlo (0.35 stacking, 0.33 max-burst). The MeV search is a genuinely new application of SNDAQ to FRBs via collective DOM hit-rate excess, searching 21 FRBs on timescales 10–1280 ms. The null result is robust, limits at 90% CL are clearly presented, and the sensitivity projections for future radio interferometers are a nice touch.\n\nSoft spots: the MeV limit is quoted for a single fiducial CCSN spectrum (mean energy 15.6 MeV, alpha=3). The authors explicitly note the hit-rate dependence on incident flux, but they do not quantify it — a harder or softer spectrum could move the limit. That makes the 'first limit on MeV neutrino emission' claim somewhat model-dependent, though not misleading, since the assumption is stated. I would have liked one plot showing how the limit shifts for other plausible spectra. Also, the MeV limits have no systematic error band, and the 3-sigma detection threshold is not corrected for trials. The trial issue is minor because the largest observed significance is 2.55 sigma, so the null result stands regardless.\n\nOverall, the citation pattern is clean — the self-citations are the prior IceCube FRB analyses that this work improves on. The paper is honest about its assumptions and the central null result is not in question. This is more of a conference-proceedings contribution than a breakthrough paper, but it is exactly the kind of reference that FRB modelers and neutrino advocates will want to cite.\n\nIf I were a journal editor, I would send this to a referee if it were submitted as a Letter or proceedings paper; it does not need major revision. The authors should be asked to add spectral-dependence quantification and a trials statement, but those are minor.","headline":"A clean null result with a real first: IceCube reports the first MeV limits and improved GeV-TeV limits on neutrino emission from FRBs, though the MeV limit rests on a stated fiducial spectrum.","tokens_in":6313,"tokens_out":2797,"would_cite":true,"duration_ms":25264,"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":"The paper reports two IceCube searches for neutrinos coincident in time and direction with fast radio bursts, found no excess, and consequently sets the first limits on MeV neutrino emission from FRBs and the tightest GeV–TeV limits to…","keywords":["fast radio bursts","IceCube","neutrino astronomy","muon neutrinos","MeV neutrinos","SNDAQ","multimessenger astronomy","upper limits"],"falsifier":"Observe a single coincident event: an IceCube muon track reconstructed within the directional uncertainty of a radio-detected FRB and inside a $\\Delta T$ window such as 10 ms, or an SNDAQ significance above the $3\\sigma$ threshold in any 10–1280 ms window around the 21 bursts, would contradict the reported null correlation. A purely archival cross-check would recompute the stacking test statistic for the 28 FRBs with the six-year high-purity track selection; if the per-burst limits for $\\Delta T < 1$ s did not improve by roughly a factor of 50 over the six-year result, the claimed sensitivity gain would fail.","tokens_in":5450,"feed_emoji":"📡","tokens_out":9192,"duration_ms":77736,"temperature":0.7,"pith_summary":"The paper attempts to establish whether fast radio bursts produce neutrinos, using two complementary IceCube searches: one for GeV–TeV muon-neutrino tracks and one for collective MeV hit-rate bursts. No statistically significant excess is found in either channel, so the authors report the first upper limits on MeV neutrino emission from FRBs and the tightest limits to date at GeV–TeV energies. If correct, the result means the observed FRBs are not, as a class, strong neutrino emitters, and it gives quantitative caps on the hadronic energy FRB progenitors can release as neutrinos. This matters because FRBs have been a candidate source of IceCube's diffuse astrophysical neutrino flux, and these limits test that possibility.","feed_headline":"No neutrinos accompany fast radio bursts, new limits show","feed_subtitle":"First MeV bounds and tightest GeV–TeV caps test whether FRBs feed IceCube's diffuse flux.","key_machinery":"The analysis rides on two likelihood engines. For GeV–TeV neutrinos, an unbinned maximum-likelihood test statistic (the paper's Eq. 2.1) compares a signal spatial PDF, a two-dimensional Gaussian around each FRB position, against a Poisson background PDF built from off-time data, and is maximized to find the best-fit number of signal events for a given time window $\\Delta T$. For MeV neutrinos, a one-dimensional Gaussian likelihood over per-optical-module (DOM) hit rates (Eq. 2.2) measures a collective rate excess $\\Delta\\mu$ in the Supernova Data Acquisition (SNDAQ) system, which records photomultiplier hits in 1.6 ms bins; the resulting significance $\\xi = \\Delta\\mu/\\sigma_{\\Delta\\mu}$ is compared with seasonally corrected off-time significances. The new leverage is that FRBs' millisecond timescales allow the track analysis to loosen its event selection, increasing effective area, especially in the Southern sky, while keeping the background penalty small.","core_discovery":"The central claim is a null result with improved constraints. In a stacking search and a max-burst search over 28 FRBs using a loosened muon-track sample, the post-trial $p$-values are 0.35 and 0.33, consistent with atmospheric background. In the SNDAQ search over 21 FRBs, no significance exceeds the one-sided $3\\sigma$ threshold, with the most significant burst at $2.55\\sigma$. From these non-detections the paper derives 90% confidence upper limits on the time-integrated neutrino flux per FRB for time windows from milliseconds to seconds, finding that for $\\Delta T < 1$ s the $E^{-3}$ stacking limits are about a factor of 50 stronger than the previous six-year analysis, and that the MeV limits are the first ever placed on FRBs.","pith_inferences":["An unstated consequence is that the quoted MeV limits are tied to the specific 15.6 MeV supernova template; repeating the SNDAQ analysis with several spectral templates would yield spectrum-independent bounds, and the paper's noted dependence of hit rate on incident flux suggests results could shift materially for harder or softer spectra.","If only a subpopulation of FRBs, such as repeaters or bursts with persistent radio emission, produce neutrinos, the stacking test dilutes the signal; as the catalog grows, splitting FRBs by class and running the max-burst test separately may reveal a signal the current 28-source sample cannot resolve.","The SNDAQ burst technique could be applied to other millisecond astrophysical transients, such as magnetar giant flares or short gamma-ray burst precursors, where MeV neutrino emission is still essentially unconstrained."],"forward_implications":["The per-burst limits at short time windows constrain any model in which a homogeneous class of FRBs produces IceCube's diffuse flux: the stacking limits provide a benchmark obtained by dividing the measured diffuse $\\nu_\\mu$ flux among thousands of FRBs per day.","The first MeV limits rule out a supernova-like neutrino flash accompanying the observed bursts; any model that gives FRB progenitors a bright MeV-neutrino counterpart at these fluences is inconsistent with the data.","The same pipeline applied to the larger FRB catalogs expected from wide-field radio interferometers should reach the diffuse-flux benchmark for Northern-Sky sources once the source class grows by about an order of magnitude.","The loosened track selection shows that millisecond timing windows can compensate for higher atmospheric background, a strategy transferable to searches for other short-duration transients."],"supporting_citations":[{"why":"Provides the six-year IceCube FRB search whose event selection, test statistic, and limits this analysis extends and improves.","marker":"[14]"},{"why":"Sets earlier per-burst neutrino limits from FRBs that the new GeV–TeV results improve on.","marker":"[13]"},{"why":"Introduces the SNDAQ hit-rate technique and its 1.6 ms binning, the basis for the MeV search.","marker":"[15]"},{"why":"Supplies the fiducial core-collapse supernova neutrino spectrum (mean 15.6 MeV, $\\alpha=3$) assumed for the MeV limits.","marker":"[20]"},{"why":"Estimates the all-sky FRB rate of thousands per day, used to draw the diffuse-flux benchmark line.","marker":"[10]"},{"why":"Gives IceCube's measured diffuse astrophysical $\\nu_\\mu$ flux, the benchmark the stacking limits are compared against.","marker":"[19]"},{"why":"Projects wide-field radio interferometer detection rates that will supply future FRB triggers.","marker":"[21]"},{"why":"Forecasts roughly one FRB per day from next-generation radio interferometers, motivating the sensitivity projections.","marker":"[22]"}],"fun_headline_variants":["IceCube finds no neutrinos from fast radio bursts","Null result: no neutrinos from FRBs, tightest limits yet","First MeV limit on FRB neutrinos, no signal found","FRB neutrinos absent in IceCube's tightest search","IceCube sets first MeV limits on FRB neutrinos"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The MeV limits assume FRB neutrinos follow a core-collapse supernova spectrum with mean energy 15.6 MeV and pinching parameter $\\alpha = 3$, chosen only because no FRB-specific neutrino spectrum model exists; the SNDAQ hit rate depends on the incident flux shape, so different spectra would change the quoted limits.","fun_headline_variants_meta":{"raw":{"variants":["IceCube finds no neutrinos from fast radio bursts","Null result: no neutrinos from FRBs, tightest limits yet","First MeV limit on FRB neutrinos, no signal found","FRB neutrinos absent in IceCube's tightest search","IceCube sets first MeV limits on FRB neutrinos"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000144,"raw_usage":{"total_tokens":1112,"prompt_tokens":821,"completion_tokens":291,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":437,"completion_tokens_details":{"reasoning_tokens":206}},"tokens_in":437,"tokens_out":291,"duration_ms":3133,"temperature":1.0,"reasoning_tokens":206,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T10:02:03.687165+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Observe a single coincident event: an IceCube muon track reconstructed within the directional uncertainty of a radio-detected FRB and inside a $\\Delta T$ window such as 10 ms, or an SNDAQ significance above the $3\\sigma$ threshold in any 10–1280 ms window around the 21 bursts, would contradict the reported null correlation. A purely archival cross-check would recompute the stacking test statistic for the 28 FRBs with the six-year high-purity track selection; if the per-burst limits for $\\Delta T < 1$ s did not improve by roughly a factor of 50 over the six-year result, the claimed sensitivity gain would fail.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the six-year IceCube FRB search whose event selection, test statistic, and limits this analysis extends and improves."},{"cited_title":"Fahey, A","cited_arxiv_id":null,"evidence_quote":"Sets earlier per-burst neutrino limits from FRBs that the new GeV–TeV results improve on."},{"cited_title":"Abbasi et al., Astron","cited_arxiv_id":null,"evidence_quote":"Introduces the SNDAQ hit-rate technique and its 1.6 ms binning, the basis for the MeV search."},{"cited_title":"Totani, K","cited_arxiv_id":null,"evidence_quote":"Supplies the fiducial core-collapse supernova neutrino spectrum (mean 15.6 MeV, $\\alpha=3$) assumed for the MeV limits."},{"cited_title":"Callister, J","cited_arxiv_id":null,"evidence_quote":"Estimates the all-sky FRB rate of thousands per day, used to draw the diffuse-flux benchmark line."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Forecasts roughly one FRB per day from next-generation radio interferometers, motivating the sensitivity projections."}],"review_version":1}