{"id":"5cddaa33-c089-4398-901e-025557a6904c","arxiv_id":"2601.20964","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"A DESI early-data search found three tidal-disruption-event-linked extreme coronal line emitters, giving a galaxy-normalized rate of 5 (+5/-3) × 10^-6 galaxy^-1 yr^-1 at z ≈ 0.2.","lead":"DESI spectra were searched for galaxies showing strong ionized-iron lines, and three are attributed to tidal disruption events, with a measured rate of about 5 per million galaxies per year. The result is consistent with earlier surveys and supports using DESI to find such rare nuclear transients.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Rate denominator depends on a single-object, host-independent X-ray-to-pEQW calibration (Eq. 4); the anchor may not transfer across DESI galaxies' continua, so R_G is not yet calibrated.","rationale":"The reader's weakest assumption correctly identifies Eq. 4 as the most load-bearing element of the rate calculation. I agree, but I sharpen the concern: the issue is not only whether a linear X-ray-to-coronal-line scaling holds, but whether AT 2017gge's pEQW-based normalization can be transplanted to galaxies with very different continua. The paper deserves credit for a transparent search, measured detection efficiency, and multiwavelength follow-up of individual candidates; the three-object sample and the consistency with previous rates are plausible. However, the central quantitative claim depends on a visibility-time denominator whose calibration is unvalidated and whose dominant systematic is not included in Table 13. A concrete recalculation using a multi-object, continuum-aware calibration would settle whether the rate shifts materially. Since the reader's verdict is already CONDITIONAL and this concern reinforces rather than overturns that assessment, no verdict change is needed.","tokens_in":58833,"tokens_out":8910,"duration_ms":103983,"concrete_test":"Recompute the total visibility time with a host-aware calibration: replace Eq. 4 with a line-luminosity conversion calibrated from the full sample of known CrL-TDEs with X-ray and coronal-line measurements (including AT 2017gge, AT 2018dyk, AT 2019azh), then for each of the 465,610 DESI galaxies convert the line luminosity to an observed line flux using luminosity distance and to pEQW using the FastSpecFit continuum at the relevant wavelengths. If the summed visibility time (and hence R_G) changes by more than a factor of 2, the quoted rate is not robust; if it changes by less than ~20%, the single-object anchor is adequate.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The headline rate R_G = 5 (+5/-3) x 10^-6 galaxy^-1 yr^-1 is the ratio of three detections to a summed visibility time. That denominator is governed by Eq. 4: S_max/S_gge = L_max/L_gge, where S is the coronal-line strength used in the detection-efficiency integral (Eq. 5). Two problems compound here. First, S_gge is AT 2017gge's pEQW — a rest-frame equivalent width — so Eq. 4 predicts a host-independent pEQW from X-ray luminosity. But pEQW for a fixed line luminosity is inversely proportional to host continuum luminosity. The 465,610 DESI galaxies span a wide range of stellar masses and continuum brightnesses; the same TDE X-ray luminosity that was detectable in AT 2017gge could be undetectable in a luminous host and detectable much longer in a faint host. This transferability error is absent from the Table 13 uncertainty budget, which only includes the uncertainty on S_gge and L_gge. Second, the absolute anchor is one object; the other ~13 known CrL-TDEs are not used to validate the scaling. Because the Poisson term already contributes +97/-54% of the uncertainty, a factor-of-two shift in the visibility-time denominator would move R_G outside the quoted range and alter the 'broadly consistent' conclusion. The search itself is careful and transparent, but the galaxy-normalized rate is not yet calibrated against host-galaxy properties.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper presents a systematic search of the DESI Early Data Release for extreme coronal line emitters (ECLEs) using the SLEIPNIR pipeline. After processing 465,610 galaxies, the authors identify 208 galaxies with Fe coronal lines and, through a multi-wavelength classification involving optical/NIR/MIR photometry, archival spectra, and new follow-up spectroscopy, classify three objects (Pidgeot, Raticate, Raichu) as TDE-linked and the remaining ~205 as AGN-related. Using the visibility-time formalism of Callow et al., calibrated with the Sazonov X-ray TDE luminosity function, the AT 2017gge coronal-line anchor, and a power-law decline over 10 years, they derive a galaxy-normalized TDE-ECLE rate R_G = 5(+5,-3) × 10^-6 galaxy^-1 yr^-1 at median z = 0.2, together with mass-normalized and volumetric rates, and compare these with previous SDSS, BOSS, and literature TDE rates. They also update the MIR colour-luminosity relation for coronal-line TDEs.","tokens_in":59256,"tokens_out":5317,"duration_ms":58526,"significance":"If the rate estimate holds, the paper roughly doubles the known sample of TDE-linked ECLEs and demonstrates that DESI EDR is an effective discovery engine for nuclear transients. The reported rate is broadly consistent with previous ECLE rates and strengthens the conclusion that only a fraction of TDEs produce strong coronal lines. The paper's strengths are its transparency and reproducibility: the search code is public, the detection efficiency is measured with simulated DESI spectra, the false-positive sources are discussed in detail, and the sample is cross-checked against an independent DESI EDR ECLE search. The multi-epoch spectroscopy and WISE/NEOWISE analysis for the three TDE candidates are careful. The main weakness is that the galaxy-normalized rate rests on a single-object, host-independent calibration between X-ray luminosity and coronal-line strength; this calibration is not included in the quoted uncertainty budget and could shift the rate outside the stated errors.","major_comments":[{"comment":"The rate denominator is controlled by Eq. (4), S_max/S_gge = L_max/L_gge, where S is a pseudoequivalent width (pEQW) as used in the detection-efficiency simulation of §3.3. For a fixed line luminosity, pEQW is inversely proportional to the host-galaxy continuum, so Eq. (4) predicts a pEQW from X-ray luminosity with no dependence on the host. The DESI EDR sample spans stellar masses down to ~10^7 M_sun (Fig. 5), and the same TDE would have substantially different visibility times in a faint versus luminous host. Table 13 includes uncertainties on S_gge and L_gge but not this host-continuum systematic. I recommend validating Eq. (4) with the other ~13 known CrL-TDEs, or converting S to line luminosity and applying per-galaxy continua from FastSpecFit, and adding the resulting systematic to the rate budget. A factor-of-two change in the summed visibility time shifts R_G outside the quoted P","section":"§6.2.1, Eq. (4); Table 13"},{"comment":"The visibility-time integral is truncated at 10 years. The power-law index is sampled down to -5/12, for which the decline over 10 years from the 218-day anchor is only a factor of roughly 0.3; a substantial fraction of the simulated population could remain above the ~1.3 Å detection threshold after the truncation. The uncertainty budget in Table 13 does not include the choice of the 10-year cutoff. Please report the sensitivity of R_G to t_max (e.g., 5, 10, and 20 years) and include the cutoff as a systematic uncertainty if it is non-negligible.","section":"§6.2.1, Eq. (5); Table 13"}],"minor_comments":[{"comment":"Several DESI target IDs in the section headings do not match Table 11. For example, §5.1.1 and §5.1.2 both list DESI 39627794400938039, while Table 11 assigns Pidgeot = 39633332819985805 and Raticate = 39627794400938039. Similar conflicts occur for Charizard and Fearow. Please correct the headings so each object has a unique, consistent ID.","section":"§5.1.1, §5.1.2, §5.2.2, §5.2.3; Table 11"},{"comment":"The Introduction refers to 'Appendix 5.2' for the CrL-AGN sample; this should likely be Appendix D or a proper section number. There is also a typo in Section 6 ('we disuses') and a repeated word in the caption of Fig. 28 ('x' after Ciii).","section":"Section 1, Section 6"},{"comment":"The entries 'AT2017gge peak CrL strength' and 'AT2017gge peak luminosity' are propagated from a single object. Clarify in the table notes that these do not include any host-continuum or transferability systematic, and that such a systematic is not yet estimated.","section":"Table 13"}],"recommendation":"major_revision","confidential_remarks":"The reader's conditional verdict is fair. I see no circularity: the rate is derived from detections and external calibrators, and is compared against, not fitted to, previous rates. The central concern is the host-independence of Eq. (4); this is a calibration problem rather than a methodological circularity, and it should be fixable by using the other known CrL-TDEs and/or per-galaxy continua. If the authors address the host-continuum dependence and the 10-year truncation sensitivity, the paper would be suitable for publication in MNRAS."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"This is a solid, incremental extension of the SLEIPNIR program to DESI EDR. The genuinely new items are three TDE-ECLE candidates, a galaxy-normalized rate at median z≈0.2, and a 205-object CrL-AGN sample that will be a useful reference for contamination studies. The rate is consistent with the SDSS Legacy and BOSS LOWZ results, which is reassuring.\n\nThe search itself is careful and transparent. Flagging criteria, false-positive diagnostics, and crossmatches are spelled out in detail, including a critical re-examination of Ding et al. (2025) where this group identifies likely artefacts. Follow-up spectra and photometry are used sensibly, and the public code/data plans are a plus. The MIR colour-luminosity relation gets a modest strengthening, with a proper treatment of fit selection. The authors also flag their own limitations: the chi-squared fit is biased by small numbers, and the ratios of TDEs producing ECLEs are upper limits because not all ECLEs may be TDEs.\n\nThe main soft spot is the visibility-time denominator. Equation 4 scales peak coronal-line strength from AT 2017gge's pEQW to sampled X-ray luminosity, but pEQW depends on host continuum brightness. The DESI sample spans a wide range of stellar masses, so the same line luminosity would give different pEQWs in different hosts. The calculation does not appear to correct for this host dependence. Because the Poisson term already contributes roughly ±50-100% uncertainty, a factor-of-two shift in the visibility-time sum would not overturn the \"broadly consistent\" conclusion, but it does mean the central rate is not yet firmly calibrated. I would like to see a systematic error term for the Eq. 4 anchor, or at least a host-mass sensitivity test. The 10-year power-law decline is a secondary assumption, though the range of indices is explored.\n\nClassification of the three candidates as TDEs is plausible but not airtight; the evidence is multi-wavelength and circumstantial. The authors acknowledge this by calling the ratios upper limits. I would want to know how the rate changes if the weakest candidate (Raichu) is dropped.\n\nThis paper deserves a serious referee. It is honest, reproducible in intent, and adds a real data point to the TDE-ECLE rate discussion. A reader working on TDEs or nuclear transients will find it worth reading and citing.","headline":"Careful, incremental DESI EDR extension of the SLEIPNIR ECLE search: three new TDE-ECLE candidates and a z≈0.2 rate, with a single-anchor visibility-time calibration that deserves a systematic-error term.","tokens_in":59911,"tokens_out":2640,"would_cite":true,"duration_ms":31801,"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":"A search of 465,610 DESI galaxies finds three new tidal-disruption 'light echoes' — galaxies whose extreme coronal emission lines betray a past stellar shredding — and measures a per-galaxy rate consistent with earlier surveys.","keywords":["extreme coronal line emitters","tidal disruption events","DESI","coronal lines","active galactic nuclei","mid-infrared variability","transient rates","galaxy spectroscopy"],"falsifier":"Measure peak X-ray luminosity and peak coronal line strength for a sample of a dozen coronal-line TDEs; if the ratio S_max/L_max scatters widely around AT 2017gge's value, the linear scaling used in Equation 4 is invalid and the reported rate would need revision. Alternatively, re-running the visibility-time calculation with a nonlinear scaling and comparing the resulting rate to the observed number of detections would settle whether the anchor assumption biases the result.","tokens_in":58740,"feed_emoji":"🔭","tokens_out":3640,"duration_ms":37400,"temperature":0.7,"pith_summary":"This paper reports the first systematic search for extreme coronal line emitters (ECLEs) in the Early Data Release of the Dark Energy Spectroscopic Instrument, identifying three galaxies whose strong, high-ionization iron lines likely arise from tidal disruption events (TDEs). Using those three detections and a Monte Carlo visibility-time calculation, the authors measure a galaxy-normalized TDE-linked ECLE rate of 5 (+5/-3) × 10^-6 per galaxy per year at median redshift z ≈ 0.2, broadly consistent with rates from SDSS and BOSS surveys. The search also yields more than 200 coronal-line AGNs, the primary astrophysical contaminants in TDE searches, providing a reference catalogue. The result matters because it demonstrates that DESI can discover these rare nuclear transients and because it tightens the fraction of TDEs that produce coronal-line echoes.","feed_headline":"Three new tidal-disruption coronal-line galaxies found","feed_subtitle":"Rate of 5 per million galaxies per year matches SDSS and BOSS, suggesting DESI will find dozens more.","key_machinery":"SLEIPNIR, a custom Python pipeline that flags ECLE candidates by scoring detections of iron coronal lines ([FeVII], [FeX], [FeXI], [FeXIV]) against strict criteria, with detection efficiency measured by planting simulated coronal lines into 10,000 real DESI spectra. The rate calculation rests on a visibility-time method: TDE peak X-ray luminosities are sampled from a luminosity function, converted to coronal line strengths using a linear scaling anchored to the TDE AT 2017gge (S_max/S_gge = L_max/L_gge), and evolved as power-law declines over 10 years, with cosmological time dilation accounted for per galaxy redshift.","core_discovery":"The central discovery is that DESI's Early Data Release contains three new TDE-linked ECLEs — Pidgeot, Raticate, and Raichu — identified by the SLEIPNIR pipeline and confirmed through multi-wavelength follow-up, and that the resulting galaxy-normalized rate, R_G = 5 (+5/-3) × 10^-6 galaxy^-1 yr^-1 at z ≈ 0.2, is consistent with previous SDSS Legacy and BOSS LOWZ rates. The paper also strengthens the mid-infrared colour-luminosity relation for coronal-line TDEs: objects with brighter MIR flares show more significant reddening at outburst, now quantified with quadratic and linear fits to the ΔW2 versus ΔW1 and Δ(W1-W2) versus ΔW2 relations.","pith_inferences":["Because the rate rests on a single anchor object, future samples of a dozen coronal-line TDEs with both X-ray and coronal-line measurements would either validate or break the linear scaling; if the scatter is large, the quoted rate uncertainties are underestimated and the rate itself would need recalibration.","The paper notes galaxies with [NeV] but no [FeVII] emission despite nearly identical ionization energies; this suggests the [NeV]/[FeVII] ratio could serve as a sensitive probe of the softness of the X-ray ionizing continuum, a diagnostic worth testing on the full DESI sample.","The hint that the volumetric ECLE rate is higher than the BOSS LOWZ rate, if confirmed with complete DESI data, would support the theoretical expectation that TDE rates decline with redshift, tying ECLE rates to the cosmic evolution of tidal disruptions."],"forward_implications":["The full DESI survey is expected to yield roughly 35–50 new TDE-linked ECLEs, enabling rate measurements with much smaller Poisson uncertainties.","The new rate point extends the galaxy-normalized ECLE rate versus stellar mass relation and keeps it consistent with the theoretical minimum TDE rate, implying that only a subset (roughly 5–50%) of TDEs produce observable coronal lines.","The 205-object CrL-AGN sample provides a reference catalogue of the primary astrophysical contaminants in optical searches for TDE-linked ECLEs.","The strengthened Δ(W1-W2) versus ΔW2 relation for coronal-line TDEs offers a mid-infrared colour diagnostic that can help separate TDEs from AGN flares."],"fun_headline_variants":["DESI's early data yields three tidal-disruption coronal galaxies","Three extreme coronal emitters discovered in DESI EDR","New TDE-linked galaxies found via DESI's coronal-line search","DESI finds trio of tidal-disruption events in initial release","Coronal-line transients: Three TDEs emerge from DESI survey"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The rate calculation assumes that a TDE's peak coronal line strength scales linearly with its peak X-ray luminosity, using the single object AT 2017gge to set the proportionality; if that scaling is not universal, the visibility times and hence the rate shift systematically.","fun_headline_variants_meta":{"raw":{"variants":["DESI's early data yields three tidal-disruption coronal galaxies","Three extreme coronal emitters discovered in DESI EDR","New TDE-linked galaxies found via DESI's coronal-line search","DESI finds trio of tidal-disruption events in initial release","Coronal-line transients: Three TDEs emerge from DESI survey"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000169,"raw_usage":{"total_tokens":1119,"prompt_tokens":780,"completion_tokens":339,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":524,"completion_tokens_details":{"reasoning_tokens":247}},"tokens_in":524,"tokens_out":339,"duration_ms":4477,"temperature":1.0,"reasoning_tokens":247,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-03T07:08:07.430748+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure peak X-ray luminosity and peak coronal line strength for a sample of a dozen coronal-line TDEs; if the ratio S_max/L_max scatters widely around AT 2017gge's value, the linear scaling used in Equation 4 is invalid and the reported rate would need revision. Alternatively, re-running the visibility-time calculation with a nonlinear scaling and comparing the resulting rate to the observed number of detections would settle whether the anchor assumption biases the result.","supporting_citations":[],"review_version":1}