{"id":"3123e8a8-7d56-4f9f-98eb-a055161fda64","arxiv_id":"1908.10031","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"HAWC reports no TeV emission from GW170817 up to about 120 days after the event and gives 1 to 100 TeV flux upper limits for it and two similar short gamma-ray bursts.","lead":"Using the HAWC gamma-ray observatory, the authors searched for very high energy TeV light from the neutron star merger GW170817 and from similar short gamma-ray bursts. They found no emission and report upper limits, but they state that these limits are not strong enough to constrain theoretical models.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The abstract's 'no counts were observed' is ambiguous and the paper gives no on-source/background counts, so the upper limits are not verifiable as stated.","rationale":"The reader's weakest assumption identifies the Poisson/normal background and the absence of a systematic error budget. My concern is adjacent but more specific: the phrase 'no counts were observed' is the empirical basis for the upper limits, and the paper never defines what it means or reports the observed and background counts that would make the meaning concrete. With an exposure of 205.27 hr, a genuinely zero-event on-source count would be exceptional and would itself indicate an analysis issue, whereas a non-significant excess is a different statement that requires reporting the actual counts and expected background. This ambiguity affects the Feldman-Cousins computation directly. At the same time, the paper's own admission that the upper limits are 'not constraining' tempers the impact: the null result is plausible and the limits are weak, so this is not a reason to reject the paper outright. Conditional acceptance remains the right posture until the counts, confidence level, and numerical limits are documented.","tokens_in":5648,"tokens_out":9952,"duration_ms":98676,"concrete_test":"For each of the 10 sliding time windows in Section 3, tabulate the number of counts in the HAWC on-source region, the expected background from the off-source/direct-integration maps, and the exposure. Recompute the Feldman-Cousins upper limits at 95% CL using these numbers, including a systematic uncertainty on the background at the level described in [23]. If any window shows a nonzero on-source count, the abstract's 'no counts' wording is inaccurate and the limits must be re-derived; if the recomputed limits differ from the plotted values by more than the line thickness in Figure 1, the reported upper limits are not reliable.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim rests on the sentence in the abstract: 'Since no counts were observed up to approximately 120 days after the trigger time, we derive and report the corresponding upper limits.' With Table 1 listing 205.27 hr of exposure for GRB 170817A, a literal zero-event observation is implausible: the source region will contain cosmic-ray background events. 'No counts' must mean either zero events after all gamma/hadron cuts, or no statistically significant excess over the background estimated by the direct-integration method referenced to [23]. These two readings lead to different Feldman-Cousins upper limits, yet Section 3 does not report the observed number of events, the expected background, or the confidence level used. The claim is therefore under-specified at the exact point where the upper limits are computed. The later sentence in Section 4, 'there was no TeV emission found,' is consistent with either reading but does not resolve it.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This ICRC2019 proceedings paper reports a HAWC search for very-high-energy (1-100 TeV) gamma-ray emission from the neutron-star merger GW170817/GRB 170817A, motivated by the late-time X-ray and radio afterglow peak around 120 days. The authors state that no counts were observed up to about 120 days after the trigger and derive upper limits using a Feldman-Cousins approach with an assumed photon spectral index of -2.5, a pivot energy of 1 TeV, and EBL attenuation. They also extend the search to a sample of similar short GRBs proposed by von Kienlin et al. (2019), reporting exposure times and upper limits for three bursts in the HAWC field of view. The paper concludes that no TeV emission was found and that the derived upper limits are not constraining compared with a synchrotron self-Compton (SSC) prediction.","tokens_in":5833,"tokens_out":2193,"duration_ms":24055,"significance":"If the result holds, the paper provides an important multi-messenger constraint: HAWC saw no TeV gamma rays from GRB 170817A in the first ~120 days, with energy-dependent upper limits in the 1-100 TeV range. The analysis is based on established HAWC methods cited to the daily-monitoring paper, uses a standard Feldman-Cousins confidence-interval approach, and explicitly compares the limits with an SSC model prediction, so the upper limits are not circularly dependent on that model. The extension to similar short GRBs is a useful first step, though the small sample and preliminary nature limit the significance. The main value is as a timely conference contribution documenting the non-detection and its limits; however, as written the paper lacks the numerical details needed to verify or use those limits.","major_comments":[{"comment":"The central claim 'Since no counts were observed up to ~120 days' is ambiguous and is not backed by the required bookkeeping. A literal reading of zero events is implausible for a 205.27 hr exposure because cosmic-ray background events will populate the source region; the sentence must mean either zero events after all gamma/hadron cuts or no statistically significant excess over an estimated background. Section 3 does not report the observed on-source counts, the expected background counts, the confidence level used, or the number of energy bins and time windows. Without these numbers, the Feldman-Cousins upper limits in Figure 1 cannot be reproduced or checked, so this is a load-bearing omission.","section":"Abstract and Section 3"},{"comment":"The upper limits themselves are never given numerically in the text. For a proceedings paper whose main result is a set of upper limits, the reader needs at least a table or a quoted flux range (e.g., the 95% confidence-level flux limits at a reference energy or in the 1-100 TeV band for each of the 10 time windows). As it stands, the only quantitative claim in the abstract is the energy range, while the actual limits are confined to a preliminary figure with no axis numbers described in the text, which is insufficient for the result to be used by the community.","section":"Section 3 and Figure 1"},{"comment":"There are several internal inconsistencies that affect the interpretation of the reported exposures and source identifications. The text gives the HAWC observation start as '2017 August 17 at 20:53 UTC' while Section 2 says the Fermi trigger was '2017 September 17 12:41:20 UTC'; the date 'GW170917' also appears. The GRB in the third row of Table 1 is labeled 'GRB 170817A' but the text in Section 4 says 'GRB 170111A' while Table 1 lists 'GRB 170111B'; the discovery text refers to 'GRB 1701817A'. These naming and date errors must be corrected because they make the exposure-time and upper-limit statements for individual bursts untrustworthy as written.","section":"Sections 2 and 3 and Table 1"},{"comment":"The discussion of the derived upper limits for GRB 150101B, GRB 170111A/B, and GRB 170817A compares limits across bursts with different redshifts and exposures, but no flux values, confidence levels, or spectral assumptions for these additional bursts are given. The statement that 'the best flux upper limit is obtained for GRB 170817A because of their closeness and medium low exposure' is not quantifiable, and the claimed behavior of limits versus time window cannot be checked. Adding a table with the numerical upper limits for the three bursts in the three time bins of Figure 2 would make the extension to the von Kienlin sample a substantive result rather than an illustration.","section":"Section 4 and Figure 2"}],"minor_comments":[{"comment":"The phrase 'aboard on the Fermi satellite' is ungrammatical; it should be 'aboard the Fermi satellite'.","section":"Abstract"},{"comment":"The date of the GRB trigger is inconsistent between Section 1/2 ('2017 September 17') and the later '2017 August 17' for the HAWC observation start. Please unify the dates, keeping GW170817's actual date of 2017 August 17.","section":"Section 1"},{"comment":"The typo 'GRB 1701817A' should be corrected to 'GRB 170817A'.","section":"Section 3"},{"comment":"The burst name is given as GRB 170111B in Table 1 but as GRB 170111A in Section 4; please make this consistent.","section":"Table 1 and Section 4"},{"comment":"The figure is labeled 'PRELIMINARY' and the caption says the solid line is the SSC prediction at 40 TeV, but the y-axis label is 'Flux Density (µJy)' and the HAWC upper limit curve has a 'x10^5' scaling that is not explained in the caption. A clear caption with the energy band and the meaning of the scaling is needed.","section":"Figure 1"},{"comment":"The sentence 'The decreasing behavior of the flux upper limits as a function of time is a clear consequence of the increasing time window' should clarify that this is true for a fixed signal model only when the assumed flux is constant; otherwise it can be misleading.","section":"Section 4"}],"recommendation":"major_revision","confidential_remarks":"This is a short, preliminary ICRC proceedings paper, so one can expect some brevity, but the missing numerical upper limits and ambiguous 'no counts' statement are not merely presentation issues: they prevent verification of the paper's central claim. The fix is straightforward—add a table of observed counts, estimated background, confidence level, and derived flux upper limits for each time window and burst—so I do not recommend rejection. I would also ask the editor to ensure the HAWC collaboration has approved the quoted limits, since the paper carries the collaboration name but is marked preliminary."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Punchline: this is a modest conference proceeding, but it does add something new — HAWC's TeV upper limits on GRB 170817A out to 120 days — and the authors are commendably honest that the limits don't constrain the models. The paper's main problem is that the central claim \"no counts were observed\" is under-specified, so the numbers can't be checked from the text.\n\nWhat's actually new: the 10 time-window upper limits for 170817A (1–100 TeV, assumed spectral index -2.5, EBL-corrected), extending the earlier 2.03-hr limit, and limits for GRB 150101B and GRB 170111A/B from the von Kienlin short-GRB sample. The method is the standard HAWC direct-integration analysis, so no new technique, but the numbers are new. The SSC comparison is clearly labeled as not constraining, which is good practice — they don't oversell.\n\nSoft spots: the abstract's \"no counts were observed up to ~120 days\" can't be literal. With 205 hours of exposure the source region is full of background events. They must mean no significant excess over the estimated background. But the paper never reports the observed counts, expected background, or the confidence level, so the Feldman-Cousins limits are not reproducible from the text. That's a real omission — the stress-test flags it correctly — but in a two-page proceeding it's the kind of thing a referee would ask for rather than a fatal flaw. There are also naming inconsistencies: GRB 170111A vs GRB 170111B in text and table, and a typo \"1701817A.\" No systematic uncertainty is given, consistent with the \"preliminary\" label on the figure.\n\nIs the central result sound? I think yes. The null detection is plausible, the analysis follows an established pipeline, and the conclusion is appropriately weak: there's no TeV excess, and the limits don't touch the SSC prediction. No circularity burden, since the model comparison is post-hoc and the limits are independent of it. The heavy citation of the second author's modeling papers is noticeable but those references are directly on-topic, so I don't count it as a flaw.\n\nWho this is for: someone compiling TeV follow-up results for GW170817 or testing whether HAWC could have seen the afterglow. They get one clear fact — HAWC covered the first 120 days and saw no significant emission. That's worth having on record.\n\nRecommendation: if this were submitted as a full journal paper, I'd send it to review with the bar that the authors report observed/expected counts and systematics. As a conference report, it's acceptable but should be treated as provisional. Engage with it lightly; cite it if you need the 120-day number. It deserves a serious referee, but mainly to force the numbers into the open.","headline":"Honest null HAWC limits for GW170817 out to 120 days, but the central 'no counts' claim is under-specified and the exact numbers aren't reproducible from the text.","tokens_in":6343,"tokens_out":4160,"would_cite":false,"duration_ms":41799,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"The HAWC observatory detected no TeV gamma-ray counts from GRB 170817A in its first ~120 days of monitoring and reports upper limits from 1 to 100 TeV.","keywords":["GW170817","GRB 170817A","very-high-energy gamma rays","TeV upper limits","HAWC observatory","short gamma-ray bursts","multi-messenger astronomy","synchrotron self-Compton"],"falsifier":"Run the same ten-window pipeline on an equal number of empty sky regions matched in zenith angle: if the distribution of significances is not normal, the Poisson background assumption fails and the quoted upper limits would be biased. Alternatively, a TeV instrument with substantially better sensitivity covering the same 120 days could detect the predicted synchrotron self-Compton component, contradicting the limits.","tokens_in":5497,"feed_emoji":"🔭","tokens_out":6825,"duration_ms":64303,"temperature":0.7,"pith_summary":"This paper reports a null result: HAWC, a wide-field TeV gamma-ray observatory, saw no very-high-energy photons from the neutron-star merger GW170817/GRB 170817A during the first $\\sim$120 days after the gravitational-wave trigger. The authors convert that silence into flux upper limits for $1$–$100$ TeV, using ten sliding time windows that reach the epoch when the X-ray afterglow peaked. They then apply the same search to three short gamma-ray bursts from a recent Fermi-GBM catalog sample selected as similar to GRB 170817A. The result matters because it closes a multi-messenger channel for the most studied astrophysical event of its kind: if any TeV counterpart existed, it was fainter than these limits.","feed_headline":"No TeV gamma rays from GW170817 in first 120 days","feed_subtitle":"HAWC's new upper limits bound 1–100 TeV emission from the neutron-star merger and three similar short bursts.","key_machinery":"The central object is HAWC's ten sliding time-window sky maps, built from sidereal-day maps separated into nine shower-multiplicity bins. The search counts events in the direction of each burst and compares them with a background model whose fluctuations are taken to be Poisson, so the significance distribution is normal; flux upper limits follow from a confidence-interval prescription applied with extragalactic background light attenuation. The maps and the background-subtraction procedure are the same machinery as HAWC's daily monitoring analysis, which makes the limits reproducible and ties the analysis to established detector response as a function of declination and shower multiplicity.","core_discovery":"The paper's central claim is that HAWC, despite continuous all-sky monitoring, recorded no gamma-ray counts attributable to GRB 170817A over ten sliding time windows spanning the first $\\sim$120 days after the gravitational-wave trigger, in the energy range $1$–$100$ TeV. This absence is presented as flux upper limits derived with a confidence-interval prescription, assuming a spectral index of $-2.5$ at a pivot energy of 1 TeV and accounting for extragalactic background light attenuation. The limits, strongest for GRB 170817A because of its closeness, are not constraining: the predicted synchrotron self-Compton flux at TeV energies lies below them. The same null result holds for the three short bursts from the recent Fermi-GBM sample that spent enough time in HAWC's field of view, with limits that improve with exposure time.","pith_inferences":["Inference: an implication left implicit in the paper is that the non-detection is consistent with an off-axis jet interpretation, where the TeV component would be delayed and faint; a more sensitive TeV instrument could test the predicted late synchrotron self-Compton component directly.","Inference: the Poisson-background assumption could be checked by running the same ten-window pipeline on off-source sky regions matched in zenith angle; a non-normal distribution of significances in such a control would shift the quoted limits.","Inference: the all-sky, high-duty-cycle monitoring demonstrated here suggests that TeV observations of gravitational-wave alerts can be performed a posteriori, without waiting for a gamma-ray trigger, and the same pipeline could be applied to future neutron-star mergers."],"forward_implications":["No TeV counts were found, so any very-high-energy component from the merger in the first 120 days must lie below the reported $1$–$100$ TeV upper limits.","The reported upper limits do not constrain the synchrotron self-Compton prediction derived from the X-ray afterglow, because the predicted flux sits below the limits.","For the three short bursts with enough HAWC exposure, no TeV excess was seen; the limits improve with longer exposure and closer redshift.","HAWC's continuous sky coverage allows TeV searches for short bursts on timescales from seconds to days, extending the analysis beyond targeted follow-up campaigns."],"supporting_citations":[{"why":"Establishes the GW170817–GRB 170817A association and the redshift used for distance and EBL assumptions.","marker":"[3]"},{"why":"Supplies the observed X-ray emission that motivates the search window and the theoretical SSC comparison.","marker":"[6]"},{"why":"Documents the rising X-ray afterglow attributed to an off-axis jet, defining the late-time window searched here.","marker":"[7]"},{"why":"Provides the Fermi-GBM catalog sample of short GRBs with characteristics similar to GRB 170817A to which the HAWC search is extended.","marker":"[22]"},{"why":"Supplies the HAWC event reconstruction, background-subtraction, and map-making procedures on which the analysis depends.","marker":"[23]"},{"why":"Describes HAWC's energy response as a function of declination, used to set the $1$–$100$ TeV sensitivity.","marker":"[24]"},{"why":"Justifies the Poisson background approximation and the normal significance distribution used for upper limits.","marker":"[25]"},{"why":"Provides the extragalactic background-light attenuation model applied when deriving the flux upper limits.","marker":"[26]"}],"fun_headline_variants":["HAWC: No TeV photons from GW170817 in 120 days","GW170817: HAWC sees nothing above 1 TeV","HAWC limits TeV emission from neutron-star merger","No TeV gamma rays from GW170817: HAWC upper limits","HAWC's null result for GW170817 and three short GRBs"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The analysis assumes that HAWC's background in each time window is exactly Poisson and that the resulting significance is normally distributed, with no unmodeled drift in detector response or cosmic-ray background over the 120 days.","fun_headline_variants_meta":{"raw":{"variants":["HAWC: No TeV photons from GW170817 in 120 days","GW170817: HAWC sees nothing above 1 TeV","HAWC limits TeV emission from neutron-star merger","No TeV gamma rays from GW170817: HAWC upper limits","HAWC's null result for GW170817 and three short GRBs"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00027,"raw_usage":{"total_tokens":1609,"prompt_tokens":914,"completion_tokens":695,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":530,"completion_tokens_details":{"reasoning_tokens":603}},"tokens_in":530,"tokens_out":695,"duration_ms":5789,"temperature":1.0,"reasoning_tokens":603,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T10:54:03.769255+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same ten-window pipeline on an equal number of empty sky regions matched in zenith angle: if the distribution of significances is not normal, the Poisson background assumption fails and the quoted upper limits would be biased. Alternatively, a TeV instrument with substantially better sensitivity covering the same 120 days could detect the predicted synchrotron self-Compton component, contradicting the limits.","supporting_citations":[{"cited_title":"Fermi GBM GRBs with characteristics similar to GRB 170817A","cited_arxiv_id":"1901.06158","evidence_quote":"Provides the Fermi-GBM catalog sample of short GRBs with characteristics similar to GRB 170817A to which the HAWC search is extended."},{"cited_title":"Observation and Spectral Measurements of the Crab Nebula with Milagro","cited_arxiv_id":"1110.0409","evidence_quote":"Justifies the Poisson background approximation and the normal significance distribution used for upper limits."}],"review_version":1}