{"id":"a6de66da-2a27-4401-af2e-a6e882ebcd9f","arxiv_id":"2506.10565","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"The paper reports the first radio detection of gamma-ray pulsar PSR J1813-1246 at 1250 MHz with FAST, and stringent upper limits for 21 other radio-quiet gamma-ray pulsars.","lead":"Using the FAST radio telescope, the authors searched 22 gamma-ray pulsars with no known radio emission and detected faint periodic pulses from one, PSR J1813-1246, for the first time. The new microjansky-level limits on the other 21 sources may reveal whether such pulsars are genuinely radio-silent or merely too faint for earlier telescopes.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Detection of PSR J1813-1246 lacks a trial-corrected false-alarm probability; single-epoch S/N ~8 is not sufficient to exclude a chance candidate from the large period-DM search space.","rationale":"The paper's central claim is the first radio detection of PSR J1813-1246. The evidence consists of four observations with consistent period and DM, and a single-epoch S/N of about 8. The paper does not provide a trial-corrected false-alarm probability, which is essential for a search over ~10^4 DM trials and ~10^6 period/harmonic bins. While the consistency across epochs is compelling, the selection was made with prior knowledge of the gamma-ray period, and the same pipeline was used for all epochs, so a systematic artifact cannot be excluded without a controlled test. The reader's verdict of CONDITIONAL is appropriate because the missing analysis is straightforward to provide and would likely settle the matter. I agree with the reader's weakest assumption. The pipeline validation using the known pulsar J0358+5413 (Section 2.3) demonstrates that the search software works, but it does not calibrate the false-alarm rate for marginal candidates. If the scramble test yields a false-alarm probability below 1e-6, the detection would be robust; otherwise, the claim should be treated as tentative. The upper-limit concerns (red noise) are secondary and do not affect the central detection claim.","tokens_in":13378,"tokens_out":12683,"duration_ms":139795,"concrete_test":"Run a Monte Carlo scramble test on the four J1813-1246 observations: for each observation, randomly permute the time-series samples (or randomize the Fourier phases) to destroy any true periodicity while preserving the noise statistics, then run the identical PRESTO periodicity search restricted to the period range 47.5-48.5 ms and DM range 200-220 pc cm^-3. Repeat 1000 times per observation and record the maximum S/N. If the observed single-epoch S/N of 8 and the four-epoch combined significance are above the 99.99th percentile of the noise distribution, the detection is statistically secure; otherwise, the claim should be downgraded.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim in Section 3.1.1 is that pulsed radio emission from PSR J1813-1246 is 'confirmed' based on four epochs with DMs of 209.33, 211.40, 209.85, and 209.65 pc cm^-3 and a maximum single-epoch S/N of about 8. The paper does not report a false-alarm probability for this candidate. The search space is large: PRESTO was run with DMs from 0 to 1000 pc cm^-3 in steps of 0.05-0.2 pc cm^-3, and over all periods and harmonics for each of the 22 sources. Section 2.2 states that each observation yields approximately 500 candidates after accel_sift, meaning that a candidate with S/N ~8 is not obviously in the extreme tail of the noise distribution. The four-epoch consistency is suggestive, but the analysis pipeline is identical across epochs, and the candidates were selected with prior knowledge of the gamma-ray period. Without a quantitative estimate of the trial factor or a Monte Carlo false-alarm rate, the observed S/N cannot be converted into a statistical significance. The claim of a 'first radio detection' thus rests on the unstated assumption that the candidate is not a systematic false positive induced by folding noisy data at a known period. This is the load-bearing assumption of the paper.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports periodicity and single-pulse searches at 1250 MHz with FAST for 22 gamma-ray pulsars classified as radio-quiet. For PSR J1813-1246 it claims the first radio detection, with a spin period of 48.08 ms, a dispersion measure of 209.85 pc cm^-3, a maximum single-epoch S/N of about 8, and an estimated flux density of about 9 uJy, based on four observations with consistent periods and DMs. For the other 21 pulsars no radio emission is found, and flux-density upper limits of a few uJy are quoted. The pipeline is validated on the known pulsar J0358+5413, and the authors discuss implications for radio and gamma-ray emission geometries and for the radio-quiet population.","tokens_in":13629,"tokens_out":5303,"duration_ms":63969,"significance":"If the J1813-1246 detection holds, this is the first radio detection of that pulsar and demonstrates FAST's ability to reach a few microjansky sensitivity for gamma-ray pulsars, a useful result for the radio-quiet pulsar population. The paper has clear strengths: the pipeline is validated on a known pulsar, the candidate is consistent with an externally measured gamma-ray period, the DM is consistent across four epochs, and the authors explicitly acknowledge that red noise can affect long-period upper limits. The main weakness is that the central detection claim lacks a trial-corrected false-alarm probability, and the flux density and DM are quoted without uncertainties. The non-detection upper limits also depend on sensitivity assumptions that are only partly quantified.","major_comments":[{"comment":"The confirmation of pulsed emission from PSR J1813-1246 is not supported by a quantitative false-alarm probability. The periodicity search produces approximately 500 candidates per observation after accel_sift (Section 2.2), and the maximum single-epoch S/N is about 8. Although the gamma-ray period reduces the search trials, the effective number of independent period-DM-harmonic trials is not reported, so a single-epoch S/N of 8 cannot be assumed significant without a trial-corrected significance estimate. Please provide a Monte Carlo false-alarm rate, an analytic trials factor, or an independent blind re-detection; this is load-bearing for the 'first radio detection' claim.","section":"Section 3.1.1"},{"comment":"The estimated flux density of approximately 9 uJy is quoted without an uncertainty or a complete list of assumed parameters beyond S/N about 8 and a duty cycle of 0.4. Please give an error budget that includes uncertainties in Tsys and gain, pulse-width measurement, off-pulse baseline or red-noise contamination, and the S/N estimate, and also report uncertainties on the four DM values (209.33, 211.40, 209.85, and 209.65 pc cm^-3). Without these, the detection cannot be compared quantitatively with the upper limits in Table 2.","section":"Section 3.1.1"},{"comment":"The flux-density upper limits for the 21 non-detections are computed with a detection threshold of S/N=7, beta=1, and an assumed 10% duty cycle, while the text acknowledges that red noise can significantly degrade sensitivity for periods longer than 100 ms. Most of the sample has periods above 100 ms, so the quoted 'several uJy' limits may be optimistic. Please quantify the red-noise degradation (e.g., with injected pulse tests or off-pulse variance measurements) or explicitly state that Table 2 and Figure 4 represent sensitivity floors rather than measured upper limits; this affects the central non-detection result.","section":"Section 3.1, Eq. (1), and Table 2"}],"minor_comments":[{"comment":"The section heading contains a typo: 'INDRUCTION' should be 'INTRODUCTION', and 'F AST' appears with an inconsistent space throughout the manuscript.","section":"Section 1"},{"comment":"The table caption and column headings are not fully self-explanatory: 'Radio-queit' is a typo for 'Radio-quiet', and the columns labeled 'JP' and '˙E' lack explicit units and definitions in the caption.","section":"Table 1"},{"comment":"Equation (5) is ambiguous: the displayed expression '(S/Npeak)2βTsys' could be misread as a squared signal-to-noise ratio, which would disagree with the standard single-pulse radiometer equation; please clarify whether the '2' is a typographical artifact or an intended factor.","section":"Section 3.2, Eq. (5)"},{"comment":"The caption states 'Column (2) to (13)' for the flux-density limits, but the table actually contains 13 flux-density columns before the reference column; please correct the column numbering or the caption text.","section":"Table 2"},{"comment":"The sentence describing the radio profile is unclear: it says the main pulse and interpulse have 'a similar W50 width of ~0.2 P, comparable to the gamma-ray profile, but with a narrower pulse width'; please rephrase to distinguish W50 from the overall pulse width.","section":"Section 3.1.1"},{"comment":"In the description of Figure 3, 'usingpaastool' and 'patto' are missing spaces; they should read 'using paas' and 'pat to' (or similar), and the software commands should be formatted consistently.","section":"Section 3.1.1"}],"recommendation":"major_revision","confidential_remarks":"The main obstacle is the absence of a trial-corrected false-alarm probability for the J1813-1246 detection. Given that the candidate is corroborated by the gamma-ray period and by four-epoch consistency, a Monte Carlo or analytic significance estimate could make the detection claim fully convincing. The paper would also be strengthened by error bars on the flux density and DM and by a quantitative treatment of the red-noise effect on the upper limits."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Bottom line: the J1813–1246 detection is likely genuine, but the paper never gives the reader a quantitative handle on why. Four independent epochs with the same spin period and a DM that stays within ~1 pc cm^-3 of 210 are hard to explain as noise, and the period agrees with the gamma-ray value. That is convincing circumstantial evidence. Yet the paper stops at a single-epoch S/N of about 8 and never reports a false-alarm probability or a combined significance across epochs. That is the main gap, and it is fixable.\n\nWhat is actually new: this is the first radio detection of J1813–1246, with an estimated flux density near 9 microJy, and the FAST 1250 MHz upper limits for the other 21 sources are the tightest published, at a few microJy. The search pipeline is standard, but it is competently run and the authors validated it on a known pulsar, J0358+5413, that happened to fall in the beam. The upper-limit table, with comparison to previous measurements at other frequencies, is genuinely useful for the radio-quiet pulsar population discussion.\n\nThe soft spots beyond the missing false-alarm analysis: the flux density and DM are quoted without error bars; the upper limits may be optimistic because red noise is only acknowledged qualitatively, not folded into the sensitivity calculation; and the spectral-index comparison in Figure 4 is explicitly approximate. None of these are fatal. The stress-test note worries about a systematic false positive from folding at a known period, but that overstates the risk. Random noise does not produce a consistent DM of ~210 pc cm^-3 in four separate observations. The detection stands on the multi-epoch consistency even if the single-epoch S/N is modest.\n\nThis paper deserves a serious referee, not a desk rejection. A referee should ask for a proper trial-corrected significance for the detection, error bars on the detection parameters, and a more careful treatment of red noise in the upper limits. Those are reasonable revision requests. I would cite this work if I were publishing on radio-quiet gamma-ray pulsars, and I would bring it to a pulsar-focused reading group. The central claim is not proved to the standard the paper claims, but the evidence is strong enough to warrant publication after revision.","headline":"The J1813-1246 detection is probably real but the paper under-reports its statistical significance; the upper limits for the other 21 pulsars are the real product.","tokens_in":14188,"tokens_out":2960,"would_cite":true,"duration_ms":38933,"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 paper reports the first radio detection of the gamma-ray pulsar PSR J1813-1246 with FAST at 1250 MHz: a pulsed signal with a 48.08 ms spin period, a dispersion measure of 209.85 pc cm^-3, and a flux density near 9 microjansky.","keywords":["radio pulsars","gamma-ray pulsars","FAST telescope","dispersion measure","periodicity search","single-pulse search","flux density upper limits","PSR J1813-1246"],"falsifier":"A new deep observation of PSR J1813-1246 at comparable sensitivity that finds no pulsed signal at $48.08$ ms with DM near $209.85\\ \\mathrm{pc\\,cm^{-3}}$, or a blind periodicity search that does not use the gamma-ray ephemeris and fails to recover the candidate, would falsify the claimed detection. The candidate must also survive standard RFI mitigation; if it is traced to a flagged frequency band or disappears when the excised channels are re-added, it is an artifact.","tokens_in":13189,"feed_emoji":"📡","tokens_out":9962,"duration_ms":99194,"temperature":0.7,"pith_summary":"The paper searches 22 gamma-ray pulsars that have never been seen at radio wavelengths, using FAST at 1250 MHz, and reports a detection for one of them, PSR J1813-1246, with a spin period of $48.08$ ms and a dispersion measure of $209.85\\ \\mathrm{pc\\,cm^{-3}}$, matching the gamma-ray period. The pulsed flux density is roughly $9\\,\\mu$Jy, far below the $30\\,\\mu$Jy threshold commonly used to label such pulsars radio-quiet. For the other 21 pulsars the search yields upper limits of a few microjansky, the most stringent available at this frequency. The authors take the detection to show that 'radio-quiet' often means 'too faint for earlier telescopes', and that deep radio observations can tie gamma-ray pulsars to distance estimates and multi-wavelength emission geometry.","feed_headline":"FAST finds radio pulses from 'radio-quiet' pulsar J1813-1246","feed_subtitle":"A 9-microjansky pulsed signal at 1250 MHz suggests many gamma-ray pulsars are just too faint for earlier telescopes.","key_machinery":"The load-bearing mechanism is de-dispersion and folding of the radio time series at the known gamma-ray spin period, using trial dispersion measures from 0 to 1000 pc cm$^{-3}$. Signals are sought both as periodic trains (periodicity search) and as isolated bright pulses (single-pulse search). The detection criterion is not a single high signal-to-noise ratio but consistency across multiple epochs: four independent observations show the same period and similar dispersion measures near $210\\ \\mathrm{pc\\,cm^{-3}}$. A pipeline-validation check on the known radio pulsar J0358+5413 demonstrates that the search would recover a normal pulsar with the same procedure. The final confirmation uses phase alignment of profiles across epochs to build an averaged pulse profile with a Monte Carlo uncertainty estimate.","core_discovery":"The central claim is that PSR J1813-1246, previously classified as a radio-quiet gamma-ray pulsar, does emit pulsed radio waves. In four FAST observations spanning 2023 to 2025, the authors find a periodic signal at $48.08$ ms with dispersion measures of $209.33$, $211.40$, $209.85$, and $209.65\\ \\mathrm{pc\\,cm^{-3}}$, adopting $209.85\\ \\mathrm{pc\\,cm^{-3}}$ for the longest integration. The combined pulse profile shows a main pulse and an interpulse with width about $0.2$ of the period, and the estimated flux density is about $9\\,\\mu$Jy. Because the period agrees with the gamma-ray period, the authors regard this as the first radio detection of this pulsar. From the dispersion measure they estimate a distance near $4$ kpc, a gamma-ray luminosity of about $5\\times10^{35}$ erg s$^{-1}$, and a gamma-ray efficiency near 8 percent, values consistent with radio-loud gamma-ray pulsars. No single pulses or periodic signals were found in the other 21 sources.","pith_inferences":["If many radio-quiet gamma-ray pulsars emit at the few-microjansky level, the radio-quiet fraction measures telescope sensitivity more than pulsar physics; a systematic deep survey of the remaining unobserved candidates could convert a substantial subset into detections.","The cross-epoch consistency that carries this paper is a good first test, but an independent detection at a different telescope or an interferometric localization of the pulsed source to the pulsar position would settle the detection more firmly.","Because pulsar spectra generally rise toward lower frequencies, even deeper detections might be achievable at 300-800 MHz, where scattering is stronger but intrinsic flux is higher; a spectral-index measurement for J1813-1246 would test this directly.","The reported $9\\,\\mu$Jy flux at 1250 MHz means that J1813-1246 would be missed by time-domain surveys with short dwell times, so sustained integrations are needed to uncover the faintest radio pulsars."],"forward_implications":["If the detection is real, PSR J1813-1246 becomes a radio-loud gamma-ray pulsar at $9\\,\\mu$Jy, and the 'radio-quiet' label becomes a sensitivity statement rather than an intrinsic property.","The dispersion measure gives a distance of roughly 4 kpc, letting the authors estimate gamma-ray luminosity and efficiency for direct comparison with the radio-loud population.","The main pulse plus interpulse profile, combined with the gamma-ray profile, constrains where in the magnetosphere the radio and gamma-ray emission originate for this pulsar.","The microjansky-level upper limits for the other 21 pulsars are sharper than earlier limits at other frequencies, providing better constraints on their radio spectra.","High spin-down energy-loss pulsars such as J1813-1246, J0359+5414, and J1907+0602 are exactly where faint radio emission has now been found, supporting the trend that radio quietness decreases with increasing energy loss rate."],"supporting_citations":[{"why":"provides the gamma-ray period and profile for PSR J1813-1246 and the catalog from which the radio-quiet sample was selected.","marker":"Abdo et al. 2013"},{"why":"supplies the gamma-ray timing ephemeris used to fold the radio observations at the known spin period.","marker":"Ray et al. 2011"},{"why":"gives the YMW16 electron-density model used to convert the measured DM into a distance estimate.","marker":"Yao et al. 2017"},{"why":"gives the NE2001 electron-density model used for the alternative distance estimate.","marker":"Cordes & Lazio 2002"},{"why":"characterizes FAST's L-band gain, system temperature, and RFI environment, which set the sensitivity limits.","marker":"Jiang et al. 2020"},{"why":"the de-dispersion, periodicity, and single-pulse search software used to process the data.","marker":"Ransom 2001; Ransom et al. 2002"},{"why":"supplies the radiometer-equation sensitivity formula used to compute minimum detectable flux densities.","marker":"Lorimer & Kramer 2004"},{"why":"provides the earlier FAST detection of another faint gamma-ray pulsar, PSR J0318+0253, that motivates the microjansky sensitivity claim.","marker":"Wang et al. 2021"},{"why":"gives the mean pulsar spectral index and scatter used to compare upper limits across frequencies.","marker":"Jankowski et al. 2018"}],"fun_headline_variants":["FAST detects radio pulses from 'radio-quiet' pulsar J1813-1246","Radio-quiet pulsar proves otherwise as FAST catches its faint radio pulses","FAST finds 9-microjansky radio signal from gamma-ray pulsar J1813-1246","First radio detection of gamma-ray pulsar J1813-1246 by FAST","FAST's deep search reveals radio pulses from supposed radio-silent pulsar"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The assumption that the weak candidate near the gamma-ray period, with a maximum single-epoch signal-to-noise ratio of about 8 and consistent dispersion measures near 210 pc cm$^{-3}$ across four epochs, is genuine pulsar emission rather than a systematic false positive produced by folding noise at a previously known period.","fun_headline_variants_meta":{"raw":{"variants":["FAST detects radio pulses from 'radio-quiet' pulsar J1813-1246","Radio-quiet pulsar proves otherwise as FAST catches its faint radio pulses","FAST finds 9-microjansky radio signal from gamma-ray pulsar J1813-1246","First radio detection of gamma-ray pulsar J1813-1246 by FAST","FAST's deep search reveals radio pulses from supposed radio-silent pulsar"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000221,"raw_usage":{"total_tokens":1446,"prompt_tokens":940,"completion_tokens":506,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":556,"completion_tokens_details":{"reasoning_tokens":394}},"tokens_in":556,"tokens_out":506,"duration_ms":5317,"temperature":1.0,"reasoning_tokens":394,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T04:23:32.414770+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A new deep observation of PSR J1813-1246 at comparable sensitivity that finds no pulsed signal at $48.08$ ms with DM near $209.85\\ \\mathrm{pc\\,cm^{-3}}$, or a blind periodicity search that does not use the gamma-ray ephemeris and fails to recover the candidate, would falsify the claimed detection. The candidate must also survive standard RFI mitigation; if it is traced to a flagged frequency band or disappears when the excised channels are re-added, it is an artifact.","supporting_citations":[{"cited_title":"A., Ajello, M., Allafort, A., et al","cited_arxiv_id":null,"evidence_quote":"provides the gamma-ray period and profile for PSR J1813-1246 and the catalog from which the radio-quiet sample was selected."},{"cited_title":"M., Manchester, R","cited_arxiv_id":null,"evidence_quote":"gives the YMW16 electron-density model used to convert the measured DM into a distance estimate."},{"cited_title":"M., & Lazio, T","cited_arxiv_id":null,"evidence_quote":"gives the NE2001 electron-density model used for the alternative distance estimate."},{"cited_title":"J., et al","cited_arxiv_id":null,"evidence_quote":"provides the earlier FAST detection of another faint gamma-ray pulsar, PSR J0318+0253, that motivates the microjansky sensitivity claim."}],"review_version":1}