{"id":"739cc879-4f1d-4128-b9f4-b4ca98f44ed8","arxiv_id":"1908.07717","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"No statistically significant very-high-energy emission was seen from four GRBs in HAWC's field of view, and new flux upper limits were set for each.","lead":"HAWC searched for very-high-energy gamma rays from four notable gamma-ray bursts and found no significant emission, producing flux upper limits for each. The limits from HAWC's wide-field, high-duty-cycle observatory constrain what models can predict for nearby and powerful bursts.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"GRB 170206A upper-limit time window is internally inconsistent: text says T90=1.2 s and 'window of T90', but Table 1 lists 6-8 s; if the limit applies to 6-8 s, the prompt-coincident claim is unsupported.","rationale":"The reader's weakest assumption was the timing mismatch between HAWC windows and the phases where VHE emission was detected or expected. I agree that this timing issue is important for the scientific interpretation, and it is explicitly visible in the text. However, the more concrete and internally checkable problem is the GRB 170206A window inconsistency: the text claims a T90 window while Table 1 lists 6-8 s. This is not merely a contextual caveat but a potential misreporting of the quoted limit's time coverage. It affects one of the four central results and should be corrected or clarified. The missing confidence levels and analysis details are also real but secondary, as they are common in conference proceedings and the underlying collaboration analyses are referenced. Because the core null detection claim is not contradicted, the appropriate verdict remains conditional rather than accept or reject. The reader's CONDITIONAL verdict is therefore unchanged in direction, though the specific reason is sharpened from a general timing caveat to an identifiable inconsistency in the GRB 170206A entry.","tokens_in":9666,"tokens_out":10728,"duration_ms":95772,"concrete_test":"Check the original HAWC analysis for GRB 170206A in Ref. [29] or [30] and determine the actual search window used for the quoted upper limit. If the window was 6-8 s (or 6-7.2 s) rather than the prompt T90 of 0-1.2 s, correct both the text and Table 1 to state that the limit applies to the first HAWC-visible interval after the trigger, not the prompt phase. Independently, for each of the four bursts, tabulate the overlap between the HAWC observation window and any reported VHE detection window (e.g., MAGIC for GRB 190114C); if no overlap exists, revise the abstract and summary to avoid implying that the limits constrain the detected emission.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central result is a set of time-windowed upper limits, so the exact time window for each limit is load-bearing. For GRB 170206A, Section 3.1 reports T90 = 1.2 s and states that the most restrictive upper limit is for the T90 window, while Table 1 lists the integration time as 6-8 s. A 1.2-s T90 cannot equal a 2-s window beginning 6 s after trigger. Either the quoted limit is not for the prompt T90 as claimed, or the table entry is wrong. If the actual window is 6-8 s, the text's implication that HAWC searched TeV emission coincident with the prompt phase is unsupported, and the limit does not constrain the prompt emission mechanism for this burst. The same class of issue affects the scientific interpretation of the other limits: for GRB 190114C, the HAWC window (5-7 h) does not overlap with the MAGIC-detected sub-TeV phase (0-20 min), and for GRB 180720B the window (18-22 h) is well after the initial afterglow. These windows are stated explicitly, so the mismatch is transparent, but it means the upper limits do not constrain the detected VHE episodes. In addition, the paper does not provide the confidence levels for the limits or enough analysis detail to verify them from the text alone, which further weakens the quantitative claim.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This ICRC proceedings paper reports a HAWC search for very-high-energy (VHE) gamma-ray emission from four gamma-ray bursts that occurred between February 2017 and January 2019: GRB 170206A, GRB 170817A, GRB 180720B, and GRB 190114C. No statistically significant excess is found, and flux upper limits are quoted for specified observation windows and energy ranges: (80-800) GeV for GRB 170206A, (7-170) TeV for GRB 170817A, (2-60) TeV for GRB 180720B, and (7-170) TeV for GRB 190114C. The limits are derived under an assumed power-law spectrum with index 2.5 and include EBL attenuation following Franceschini et al. (2008). The paper frames these results as part of HAWC's ongoing GRB monitoring program, including both external-trigger follow-up and self-triggered searches.","tokens_in":9943,"tokens_out":2158,"duration_ms":21958,"significance":"If the quoted upper limits are reliable, they provide genuinely new observational constraints in the GeV-TeV band for four bursts that are of particular interest because of their proximity, energetics, or association with a gravitational-wave event. The analysis is self-contained in the sense that no model parameter is fitted to the HAWC data being constrained; the assumed spectral index, redshift, and EBL model are external inputs. A strength of the HAWC approach is its wide field of view and high duty cycle, which allow prompt and delayed coverage that pointed IACTs cannot provide. The paper also demonstrates coordination with multi-messenger and multi-wavelength observations, which is valuable. The main limitations are that the proceedings format omits the statistical details needed to verify the limits and that the observation windows for GRB 180720B and GRB 190114C do not overlap with the epochs when VHE emission was detected by other instruments.","major_comments":[{"comment":"There is a direct inconsistency between the text and Table 1 for GRB 170206A. Section 3.1 states that the GBM T90 duration is 1.2 s and that the most restrictive upper limit is for a time window of T90, but Table 1 lists the integration time as 6-8 s. A 1.2-s window beginning at the trigger cannot be the same as a 2-s window starting 6 s after the trigger. If the limit actually applies to 6-8 s after trigger, then the statement that HAWC searched for TeV emission coincident with the prompt phase is unsupported, and the quoted upper limit does not constrain the prompt-emission mechanism for this burst. This inconsistency must be resolved, since the time window is load-bearing for the scientific interpretation of the limit.","section":"Sec. 3.1 and Table 1"},{"comment":"For GRB 190114C and GRB 180720B, the HAWC observation windows do not overlap with the periods during which VHE emission was detected or is most plausibly expected. GRB 190114C was detected by MAGIC during the first 20 minutes after the trigger, whereas the HAWC limit is for 5-7 hours after the trigger; GRB 180720B was observed by H.E.S.S. during the first few hours, whereas the HAWC limit is for 18-22 hours after the trigger. The paper states these windows explicitly, so the mismatch is transparent, but the abstract and Section 4 should avoid implying that these limits constrain the detected VHE episodes. As written, the central claim 'VHE upper limits... were derived around the positions of' these bursts is technically true, but the interpretation that these limits are competitive with or complementary to the IACT detections requires clarification of what physical phases are actually being constrained.","section":"Secs. 3.3, 3.4, and 4"},{"comment":"The paper does not report the confidence level of the upper limits, the statistical significance of the non-detection, or the systematic uncertainties entering the flux calculation. Since the central result is a set of upper limits, the reader cannot verify from the text whether the quoted values correspond, for example, to 90%, 95%, or 99% confidence, nor how the assumed spectral index of 2.5 and the assumed redshift of z=0.3 for GRB 170206A propagate into the limits. The paper cites prior HAWC analysis references, which is appropriate, but it should at least state the confidence level and the dominant systematic uncertainties for these specific limits.","section":"Secs. 3 and 4 and Table 1"}],"minor_comments":[{"comment":"The Summary states 'GRB 180721A', but the burst analyzed throughout the paper is GRB 180720B; this appears to be a typo and should be corrected.","section":"Section 4"},{"comment":"The text states that the upper limit for GRB 170206A was calculated for 'Eiso = 5.5 x 10^52 erg and an assumed z=0.3', but no uncertainty on Eiso or a justification for the assumed redshift is given; since this burst has no measured redshift, the sensitivity of the quoted limit to this assumption should be stated.","section":"Section 3.1"},{"comment":"References [26] and [31] appear to cite the same GCN circular for GRB 170206A and should be merged or distinguished; similarly, several GCN entries in the reference list are incompletely formatted (e.g., entries [59], [60], [62], [63], [67], [68], [69], [70] lack titles).","section":"References"}],"recommendation":"major_revision","confidential_remarks":"The paper is a conference proceedings contribution, and the standard of detail expected is lower than for a full journal article. However, the time-window inconsistency for GRB 170206A is a factual discrepancy that affects the scientific claim, and the missing statistical context (confidence levels, significances, systematics) makes the central numerical results difficult to assess. These issues are fixable within the scope of the manuscript, so I recommend major revision rather than rejection. The paper would also benefit from a clearer statement of which physical epochs are actually constrained by each upper limit."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Short version: this is a modest ICRC proceedings note, not a major result, but it is worth knowing because it contains the first HAWC upper limits at late times for GRB 180720B and GRB 190114C. The 190114C number is the one people will look at, since MAGIC saw sub-TeV emission in the first 20 minutes and HAWC's 7-170 TeV limit covers 5-7 hours after trigger. That limit does not bear on the MAGIC-detected episode, and the paper does not claim it does (mostly), but readers should not treat it as a constraint on the prompt or early afterglow phase.\n\nWhat is new: the two new limits, plus a long-timescale (10-110 day) TeV limit for GRB 170817A that is quite restrictive. The analysis follows HAWC's standard pipeline, referenced to earlier papers, and the non-detections are not fitted to the bursts, so there is no circularity problem. Collaboration proceedings of this type normally do not show all systematics; that is expected here, but it does mean the numbers should be used with the caveat that confidence levels are not given in the text.\n\nThe soft spots: the GRB 170206A time window is internally inconsistent. The text reports T90 = 1.2 s and says the most restrictive limit is for the T90 window; Table 1 lists 6-8 s. One of those two statements is wrong. If the real integration is 6-8 s, the prompt-coincident wording is unsupported and the limit only applies starting about 6 s after trigger, which is still prompt-ish but not T90. The authors need to correct this before anyone quotes that number. Also, the assumed spectral index of 2.5 and the ad hoc z = 0.3 for GRB 170206A are external inputs that shift the limit; that is normal for this kind of search, but should be flagged in a table footnote. Minor: the summary text says GRB 170721A where it must mean GRB 170206A. And the paper gives no confidence level for the limits; a serious referee should ask for it.\n\nBottom line: for someone compiling VHE GRB upper limits, this is a citable source for two new limits and one useful long-term GW170817 constraint. It is not a paper that changes practice, and it needs a small but real correction. If I were an editor I would send it to a referee rather than desk-reject, mainly to force the authors to fix the time-window issue and state confidence levels.","headline":"Modest but useful HAWC proceedings: two genuinely new late-time upper limits, one internal time-window inconsistency that must be fixed before anyone quotes the GRB 170206A number.","tokens_in":10513,"tokens_out":3660,"would_cite":true,"duration_ms":36060,"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":"HAWC finds no very-high-energy signal in four gamma-ray bursts","keywords":["gamma-ray bursts","very-high-energy gamma rays","HAWC observatory","flux upper limits","GeV-TeV emission","GRB afterglows","gravitational-wave counterpart"],"falsifier":"A direct check is to re-run the HAWC search in the same four time windows with the latest event reconstruction and look for a statistically significant excess at the burst positions: a positive detection would contradict the paper's non-detection claim. A sharper test for GRB 190114C is to extrapolate the early MAGIC spectrum to 5-7 hours using a typical afterglow decay and compare it with the quoted $4.46\\times10^{-8}\\ \\mathrm{erg\\,cm^{-2}\\,s^{-1}}$ limit; if the predicted late-time flux exceeds the limit, the non-detection would require a spectral break or a steeper temporal decay.","tokens_in":9457,"feed_emoji":"🔭","tokens_out":8274,"duration_ms":74074,"temperature":0.7,"pith_summary":"The paper reports the results of the HAWC observatory's ongoing search for very-high-energy photons from gamma-ray bursts. For four bursts that occurred in HAWC's field of view between February 2017 and January 2019 (GRB 170206A, GRB 170817A, GRB 180720B, and GRB 190114C), the analysis finds no statistically significant excess of counts and derives GeV-TeV flux upper limits. The limits apply to specific time windows, some of which begin hours after the trigger and one of which extends over many days. These are ground-based very-high-energy constraints on some of the nearest and most studied bursts of that period, including the gravitational-wave counterpart GRB 170817A and the burst for which MAGIC reported sub-TeV photons, GRB 190114C.","feed_headline":"HAWC finds no very-high-energy signal in four gamma-ray bursts","feed_subtitle":"Upper limits for 2017-2019 bursts include the gravitational-wave counterpart GRB 170817A and a burst seen at sub-TeV energies.","key_machinery":"The central object is the HAWC water-Cherenkov array, a ground-based detector at 4,100 m elevation that observes air showers from 100 GeV to 100 TeV with a wide field of view of about 2 sr and a duty cycle above 95%. Because it does not need to repoint, HAWC can collect data before, during, and after a burst trigger, and the paper uses two search modes: rapid-response follow-up of satellite alerts and a self-triggered all-sky search over 0.2, 1, and 10 s windows. The upper limits are built from count excesses in the direction of each burst within the chosen time windows, using a spectral index of 2.5 and the extragalactic background light model to convert counts to flux limits.","core_discovery":"On its own terms, the central claim is that HAWC saw no statistically significant very-high-energy emission from any of the four bursts during the periods it was observing, and that the resulting upper limits are: $2.82\\times10^{-6}\\ \\mathrm{erg\\,cm^{-2}\\,s^{-1}}$ over 80-800 GeV for GRB 170206A in the 6-8 s window, $3.37\\times10^{-12}\\ \\mathrm{erg\\,cm^{-2}\\,s^{-1}}$ over 7-170 TeV for GRB 170817A averaged over 10-110 days, $1.81\\times10^{-8}\\ \\mathrm{erg\\,cm^{-2}\\,s^{-1}}$ over 2-60 TeV for GRB 180720B in the 18-22 hour window, and $4.46\\times10^{-8}\\ \\mathrm{erg\\,cm^{-2}\\,s^{-1}}$ over 7-170 TeV for GRB 190114C in the 5-7 hour window, all assuming a power-law spectrum with photon index 2.5 and including extragalactic background light attenuation. For GRB 190114C, this limit applies several hours after the sub-TeV emission detected by MAGIC in the first 20 minutes, so the two measurements probe different phases.","pith_inferences":["Because HAWC's windows for GRB 180720B and GRB 190114C begin 18 and 5 hours after trigger, these upper limits probe the late afterglow, not the prompt or early-emission phase that imaging atmospheric Cherenkov telescopes can catch; a burst whose very-high-energy emission is confined to the first minutes could evade both types of constraint if the two observations do not overlap.","A testable extension is to stack HAWC limits for many bursts with similar redshifts to place a population-level constraint on very-high-energy afterglow luminosity, something a single burst cannot provide.","For GRB 170817A, the long integration window dilutes any short-lived TeV flare; a time-resolved search within the 10-110 day window could reveal emission that the time-averaged limit hides."],"forward_implications":["If the non-detections are real, the four bursts produced no very-high-energy flux above the quoted limits in HAWC's time windows, so any model predicting a detectable signal in those windows is ruled out.","For GRB 190114C, the HAWC limit at 5-7 hours does not conflict with the sub-TeV emission seen in the first 20 minutes; instead it tightens constraints on a prolonged TeV afterglow at later times.","For GRB 170817A, the 10-110 day limit means that any TeV emission from the neutron-star merger afterglow during this period was fainter than $3.37\\times10^{-12}\\ \\mathrm{erg\\,cm^{-2}\\,s^{-1}}$, complementing late-time radio and X-ray observations.","Because the limits all assume a common power-law index of 2.5, they can be compared directly across bursts and folded into population studies of gamma-ray burst very-high-energy emission."],"supporting_citations":[{"why":"Establishes the HAWC upper-limit search methodology on GRB 130427A, the template this analysis follows.","marker":"[22]"},{"why":"Provides the details of the HAWC GRB monitoring program, including the triggered and self-triggered search modes.","marker":"[24]"},{"why":"Supplies the extragalactic background light attenuation model used to convert HAWC counts into flux upper limits.","marker":"[25]"},{"why":"Gives the assumed redshift and isotropic energy used for the GRB 170206A upper-limit calculation.","marker":"[29]"},{"why":"Motivates the T90, 3×T90, and 10×T90 time windows for GRB 170206A and identifies the most restrictive window.","marker":"[30]"},{"why":"Defines when GRB 170817A entered HAWC's field of view, roughly 8 hours after the gravitational-wave trigger.","marker":"[47]"},{"why":"Provides the 10-110 day search for GRB 170817A and the most constraining TeV upper limit for that burst.","marker":"[49]"},{"why":"Reports the MAGIC detection of sub-TeV emission from GRB 190114C in the first 20 minutes, setting the context for HAWC's later-time limit.","marker":"[68]"}],"fun_headline_variants":["HAWC sees no very-high-energy photons in four GRBs","No VHE signal: HAWC upper limits on four GRBs","Four GRBs, zero VHE detections for HAWC","HAWC constraints: no high-energy emission from 4 bursts","No VHE glow: HAWC's null result on four GRBs"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the chosen HAWC observation windows overlap with the periods when very-high-energy emission could plausibly be present; for GRB 190114C the limit starts five hours after the trigger, well after the sub-TeV emission detected in the first 20 minutes, so if very-high-energy emission is confined to early phases, the upper limits do not constrain the burst mechanism.","fun_headline_variants_meta":{"raw":{"variants":["HAWC sees no very-high-energy photons in four GRBs","No VHE signal: HAWC upper limits on four GRBs","Four GRBs, zero VHE detections for HAWC","HAWC constraints: no high-energy emission from 4 bursts","No VHE glow: HAWC's null result on four GRBs"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000724,"raw_usage":{"total_tokens":3273,"prompt_tokens":997,"completion_tokens":2276,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":613,"completion_tokens_details":{"reasoning_tokens":2187}},"tokens_in":613,"tokens_out":2276,"duration_ms":108316,"temperature":1.0,"reasoning_tokens":2187,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T11:57:31.036487+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A direct check is to re-run the HAWC search in the same four time windows with the latest event reconstruction and look for a statistically significant excess at the burst positions: a positive detection would contradict the paper's non-detection claim. A sharper test for GRB 190114C is to extrapolate the early MAGIC spectrum to 5-7 hours using a typical afterglow decay and compare it with the quoted $4.46\\times10^{-8}\\ \\mathrm{erg\\,cm^{-2}\\,s^{-1}}$ limit; if the predicted late-time flux exceeds the limit, the non-detection would require a spectral break or a steeper temporal decay.","supporting_citations":[{"cited_title":"Results from the first one and a half years of the HAWC GRB program","cited_arxiv_id":"1801.01437","evidence_quote":"Provides the details of the HAWC GRB monitoring program, including the triggered and self-triggered search modes."},{"cited_title":"Dichiara, M","cited_arxiv_id":null,"evidence_quote":"Motivates the T90, 3×T90, and 10×T90 time windows for GRB 170206A and identifies the most restrictive window."},{"cited_title":"Galván, N","cited_arxiv_id":null,"evidence_quote":"Provides the 10-110 day search for GRB 170817A and the most constraining TeV upper limit for that burst."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Reports the MAGIC detection of sub-TeV emission from GRB 190114C in the first 20 minutes, setting the context for HAWC's later-time limit."}],"review_version":1}