{"id":"ee272144-84e9-45be-9309-d31f511d20a2","arxiv_id":"2501.01485","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"A near-infrared spectrum of the typical superluminous supernova SN 2024ahr shows no He I at 2.058 micrometers, setting an upper limit of about 0.05 solar masses of helium in the outer ejecta.","lead":"Astronomers found no helium in the outer layers of a nearby superluminous supernova, SN 2024ahr, using a high-quality near-infrared spectrum. The result supports the idea that typical superluminous supernovae explode from stars stripped of both hydrogen and helium.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"TARDIS upper limit on helium in SN 2024ahr rests on an unvalidated He I 2.058 µm line-strength calibration; a factor-of-few error would weaken the Ic-like progenitor conclusion.","rationale":"The central claim is the non-detection of He I 2.058 µm and the resulting 0.05 M_sun upper limit. The observed non-detection itself is plausible given the high-S/N spectrum, but the scientific conclusion depends entirely on the TARDIS conversion from line depth to helium mass. That conversion is the most insecure step: it is unvalidated, unreproducible from the text, and physically incomplete with respect to non-thermal excitation. The proposed SN 2019hge test is decisive because it checks the same code and the same line against the one positive SLSN-I example; if TARDIS reproduces that detection with a sensible helium mass, the upper limit gains credibility, and if not, the Ic-like conclusion is unsupported. The paper's own words in §4 ('rough upper limit') acknowledge the fragility. The reader's CONDITIONAL verdict is appropriate; the paper should either add model validation (e.g., the SN 2019hge check and/or a non-thermal code comparison) and quote the model inputs, or weaken the claim to 'no helium detected in the outer ejecta' without a firm mass limit. Therefore the verdict remains CONDITIONAL.","tokens_in":20468,"tokens_out":8781,"duration_ms":86010,"concrete_test":"Run TARDIS on the +34 d NIR spectrum of SN 2019hge, using that event's own photometric and spectroscopic parameters (luminosity, ejecta mass, velocity, temperature, density, abundances), and vary the helium mass to reproduce the claimed He I 2.058 µm absorption. If the model cannot reproduce the observed line with any helium mass consistent with SN 2019hge's other properties, or requires a mass differing by more than ~0.05 M_sun from the value implied by Yan et al. (2020), then the TARDIS line-strength calibration used for SN 2024ahr is unreliable and the upper limit must be revisited.","verdict_should_be":"UNCHANGED","load_bearing_attack":"In §3.3, the 0.05 M_sun upper limit is set by three TARDIS models (0, 0.025, 0.05 M_sun added to the outer ejecta) after 'luminosity, ejecta mass, velocity, temperature, density, and abundances [were] adjusted to match' the observations. The model parameters are not quoted, no uncertainty or goodness-of-fit is reported, and the model is not validated for He I 2.058 µm formation in SLSNe-I at +43 d. TARDIS's treatment of this line likely does not capture the non-thermal excitation (from the magnetar and from radioactive decay) that is known to be important for He I 2.058 µm in stripped-envelope SNe (Hachinger et al. 2012; Teffs et al. 2020). If the true line is weaker than TARDIS predicts for a given helium mass, a non-detection would be consistent with M_He > 0.05 M_sun, and the conclusion that SN 2024ahr is Ic-like would not follow. The abstract's phrase 'hydrogen- and helium-stripped (Ic-like) progenitor' also overstates the paper's own 'outer ejecta' qualifier. The reader's weakest_assumption identifies the same TARDIS dependence; I agree and add the non-thermal mechanism as a specific reason to doubt the calibration.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents multi-band UV/optical photometry, optical spectroscopy, and a Gemini-South near-IR spectrum of SN 2024ahr, a hydrogen-poor superluminous supernova at z=0.0861. The authors determine the redshift from host-galaxy lines, characterize a typical SLSN-I light curve (M_g ≈ M_r ≈ −21 mag, rise and decline times near 40 and 80 rest-frame days), fit a magnetar spin-down model with P_spin ≈ 3.3 ms, B ≈ 6×10^13 G, and M_ej ≈ 9.5 M_sun, and use a +43 d rest-frame NIR spectrum to search for He I λ2.058 μm. No significant He I absorption is detected; TARDIS models with helium added to the outer ejecta predict a detectable feature at 0.05 M_sun, which the authors adopt as a rough upper limit and use to argue that the progenitor was Ic-like, i.e., stripped of both hydrogen and helium.","tokens_in":20815,"tokens_out":6567,"duration_ms":66370,"significance":"The non-detection is a useful addition: SN 2024ahr is among the nearest typical SLSNe-I, the NIR spectrum has high signal-to-noise, and the identifications of Mg I λ1.575 μm and the Mg II/Co II blend are credible and place the event closer to Type Ic than Type Ib in the NIR. The compilation of the small existing NIR SLSN-I sample is also valuable, and the authors are appropriately cautious in places, noting that the limit applies to the outer ejecta. The helium limit is not circular: the TARDIS calculation is a forward sensitivity test rather than a fit to the non-detection. The main weakness is that the quantitative helium mass limit and the Ic-like progenitor conclusion rest on a single TARDIS line-formation calculation whose inputs and validation are not reported, so the central claim is not yet fully supported.","major_comments":[{"comment":"The TARDIS models that set the 0.05 M_sun limit are not reproducible from the text. The authors state that luminosity, ejecta mass, velocity, temperature, density, and abundances were adjusted to match the photometric and spectroscopic properties, but none of these values is quoted and no goodness-of-fit statistic or uncertainty is given. Because the upper limit is entirely a prediction of this model, the adopted parameter set and its justification must be provided, at minimum in a table or appendix, before the limit can be assessed.","section":"§3.3, Figure 7"},{"comment":"The He I λ2.058 μm line-strength calibration is not validated at the relevant phase. TARDIS's standard treatment does not include non-thermal excitation from magnetar spin-down or radioactive decay, which is known to affect He I line formation in stripped-envelope supernovae (Hachinger et al. 2012; Teffs et al. 2020), and no comparison to He lines in SNe Ib/c at similar phases is shown. A factor-of-few error in the predicted line strength would change the mass limit in either direction; the paper should quantify this sensitivity, for example by varying the TARDIS inputs or cross-checking against a He-rich SN, before calling the limit conservative.","section":"§3.3, Figure 7"},{"comment":"The statement that the progenitor was stripped of both hydrogen and helium and is therefore Ic-like goes beyond the analysis, since the upper limit applies only to helium in the outer ejecta at +43 d and does not exclude helium at lower velocities or in mixed regions. Please soften the conclusion to 'the outer ejecta are helium-poor' or explicitly discuss how the outer-ejecta limit maps to a full progenitor-stripping conclusion.","section":"Abstract and §4"}],"minor_comments":[{"comment":"The word 'metalicity' should be 'metallicity'; the sentence introducing the R23 diagnostic also reads awkwardly and should be rephrased.","section":"§3.2"},{"comment":"There are small typographical issues in the caption and text: 'aout 6000 km s−1' should be 'about 6000 km s−1', and the sentence describing SN 2019hge contains a misplaced period.","section":"§3.3, Figure 4 caption"},{"comment":"The text has 'hogher expansion velocities', which should be 'higher expansion velocities'.","section":"§4"},{"comment":"The caption has 'Wavelngth' instead of 'Wavelength'; in addition, the comparison phases range from +34 to +101 d, so the text should state explicitly that this spread is a caveat for the comparison.","section":"Figure 6 caption"},{"comment":"The abstract calls the upper limit 'conservative' while the conclusions call it 'rough'; please reconcile the terminology and state the dominant systematic uncertainty.","section":"Abstract and §4"}],"recommendation":"major_revision","confidential_remarks":"The photometric and spectroscopic characterization of SN 2024ahr is solid, and the non-detection of He I is credible. The main barrier is the TARDIS-based helium mass limit: the model inputs are not given and the line-formation accuracy is unvalidated. If the authors provide the model parameters, a sensitivity analysis, or a validation against He line formation in SNe Ib/c at comparable phases, I would be willing to accept the paper. The abstract and conclusions should also be toned down to match the outer-ejecta qualifier."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The real news here is the spectrum: a high-S/N NIR spectrum of a normal, luminous SLSN-I at +43 d showing no He I 2.058 µm absorption, plus a sensible point that the handful of SLSNe-I with existing NIR spectra are mostly peculiar (low-luminosity, PISN candidate, or contested optical helium claims). That makes SN 2024ahr the first typical event probed at this line, and the comparison plot in Figure 6 is a genuinely useful synthesis. The light-curve characterization and magnetar fit are routine but solid, and the paper is honest about the \"rough\" nature of its limit in the text, even if the abstract's \"conservative\" and \"Ic-like\" wording overshoots.\n\nWhere I part company with the reader's conditional verdict is only in degree, not direction. The central non-detection is almost certainly robust; the problem is the 0.05 M_sun upper limit. The TARDIS model is described as having luminosity, ejecta mass, velocity, temperature, density, and abundances \"adjusted to match\" the observations, but none of those inputs are quoted, no goodness-of-fit or uncertainty is given, and the model's ability to form He I 2.058 µm in SLSNe at this phase is not validated. The stress-test note adds a specific and reasonable mechanism: non-thermal excitation from the magnetar and radioactive decay is known to matter for this line in stripped-envelope SNe (the paper itself cites Teffs et al. 2020), and TARDIS as used here probably does not capture it. If the true line is weaker for a given helium mass, the limit is not conservative; it is just a model prediction. So the quantitative limit is soft, and the leap from \"no helium in the outer ejecta\" to \"hydrogen- and helium-stripped (Ic-like) progenitor\" is too fast when the inner ejecta may retain helium that is hidden at this phase.\n\nNone of this is fatal. The data are new, the non-detection is useful, and the comparative argument is worth having. What the paper needs is a revision that reports the TARDIS inputs, adds an uncertainty estimate or a grid over plausible parameters, acknowledges the non-thermal excitation caveat, and softens the abstract to match the \"outer ejecta\" qualifier. For the record, the circularity concern from the reader is misplaced: the helium is added as a forward test after the model is tuned to the helium-free spectrum, so there is no fitting to the non-detection.\n\nWho gets value: anyone working on SLSN progenitors or on helium diagnostics in stripped-envelope transients. The comparison sample and the selection-effect point will be cited. Send it to a serious referee; with the model details and a more careful conclusion, it would be a solid paper.","headline":"A clean NIR helium non-detection for a typical SLSN-I, with a model-dependent mass limit that needs more transparency before the Ic-like conclusion can carry much weight.","tokens_in":21413,"tokens_out":1753,"would_cite":true,"duration_ms":20156,"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":"This paper argues that the superluminous supernova SN 2024ahr carries no detectable helium in its outer ejecta, with a conservative upper limit near 0.05 solar masses, indicating a hydrogen- and helium-stripped, Ic-like progenitor.","keywords":["superluminous supernova","SN 2024ahr","helium abundance","near-infrared spectroscopy","Type Ic supernova","stripped-envelope supernova","magnetar engine","spectral synthesis"],"falsifier":"A later or deeper near-infrared spectrum of SN 2024ahr that reveals absorption at the blueshifted position of He I $\\lambda2.058\\,\\mu\\mathrm{m}$ would overturn the conclusion that the outer ejecta are helium-free. An independent spectral synthesis calculation showing that $0.05\\,M_\\odot$ of helium in the adopted ejecta produces no detectable absorption at that wavelength would invalidate the upper limit, since the limit is set by the predicted visibility of that feature.","tokens_in":20284,"feed_emoji":"💥","tokens_out":17437,"duration_ms":142624,"temperature":0.7,"pith_summary":"SN 2024ahr is a hydrogen-poor superluminous supernova at redshift $z=0.0861$ whose multi-band light curves and optical spectra identify it as a typical member of the luminous SLSN-I population. The central result is that a high signal-to-noise near-infrared spectrum taken 43 days after peak shows no absorption at the He I $\\lambda2.058\\,\\mu\\mathrm{m}$ line, the cleanest helium diagnostic available for stripped-envelope supernovae. Spectral synthesis models convert this non-detection into a conservative upper limit of roughly $0.05\\,M_\\odot$ of helium in the outer ejecta, indicating that the progenitor lost both its hydrogen and helium layers before exploding. This matters because it shows that a reliable helium measurement is possible for a prototypical SLSN-I, not just for the peculiar events that dominate the existing near-infrared sample, and it opens a direct way to measure how many SLSNe-I explode helium-stripped rather than helium-rich.","feed_headline":"SN 2024ahr shows no helium, pointing to a stripped progenitor","feed_subtitle":"A high-quality near-IR spectrum at day 43 caps helium in the outer ejecta at about 0.05 solar masses.","key_machinery":"The central probe is the He I $\\lambda2.058\\,\\mu\\mathrm{m}$ line, the strongest near-infrared helium line that does not suffer serious blending with ejecta features such as C I or Mg II, so its absence is directly interpretable as an absence of helium in the line-forming region. The mass limit is carried by a Monte Carlo spectral synthesis model of the ejecta, tuned to match SN 2024ahr's luminosity, velocity, temperature, density, and non-helium abundances, in which helium masses of 0, 0.025, and $0.05\\,M_\\odot$ are added to the outer layers. The model that reproduces the observed spectrum also predicts that $0.05\\,M_\\odot$ of helium would create a noticeable absorption feature at $2.058\\,\\mu\\mathrm{m}$, and no such feature appears in the data.","core_discovery":"The paper establishes that SN 2024ahr is a normal, luminous SLSN-I (peak $M_g\\approx M_r\\approx -21$ mag, with magnetar spin-down parameters $P_\\mathrm{spin}\\approx3.3$ ms, $B\\approx5\\times10^{13}$ G, and $M_\\mathrm{ej}\\approx9.5\\,M_\\odot$) and that its +43 day near-infrared spectrum shows no significant absorption at He I $\\lambda2.058\\,\\mu\\mathrm{m}$. Spectral synthesis modeling places a conservative upper limit of $\\sim0.05\\,M_\\odot$ on the helium mass in the outer ejecta, so the progenitor was stripped of both hydrogen and helium and exploded as an Ic-like object. The same spectrum shows broad Mg I $\\lambda1.575\\,\\mu\\mathrm{m}$ and a Mg II $\\lambda2.136\\,\\mu\\mathrm{m}$ + Co II $\\lambda2.126\\,\\mu\\mathrm{m}$ blend, features typical of Type Ic supernovae but at higher velocities, and the paper argues that SN 2024ahr is a typical SLSN-I, unlike the peculiar events that make up the existing near-infrared sample.","pith_inferences":["If this upper limit is representative, optical helium searches in SLSNe-I should generally fail, because optical He I lines require helium masses of roughly 0.2-1.0 $M_\\odot$ to be visible, while the near-infrared line probes below $0.05\\,M_\\odot$.","A testable extension is late-time nebular spectroscopy of SN 2024ahr: a helium-poor CO-core explosion should show strong oxygen and carbon emission with little or no helium recombination emission, directly checking the Ic-like interpretation.","Because SN 2024ahr is one of the nearest SLSNe-I, the same observing strategy can be repeated for a modest sample of $z\\lesssim0.1$ events; if most show no He I $2.058\\,\\mu\\mathrm{m}$ absorption, the Ic-like channel dominates the population, while occasional detections would reveal a minority Ib-like path."],"forward_implications":["SN 2024ahr's progenitor was stripped of both hydrogen and helium before explosion, placing the event in the Ic-like subclass rather than the Ib-like subclass.","The He I $\\lambda2.058\\,\\mu\\mathrm{m}$ line is a usable helium search tool for SLSNe-I at $z\\lesssim0.1$ with ground-based 8-meter telescopes, as demonstrated by this observation.","The current near-infrared sample of SLSNe-I is dominated by unusual events (low-luminosity, a pair-instability candidate, and an optical helium claim not confirmed at $2.058\\,\\mu\\mathrm{m}$), so SN 2024ahr gives the cleanest benchmark for a typical SLSN-I.","A larger, unbiased near-infrared survey of prototypical SLSNe-I would constrain the fraction of hydrogen-poor superluminous explosions that retain helium, testing the possible evolutionary paths to these events.","The inferred magnetar parameters ($P_\\mathrm{spin}\\approx3.3$ ms, $B\\approx5\\times10^{13}$ G, $M_\\mathrm{ej}\\approx9.5\\,M_\\odot$) are typical of the SLSN-I population, supporting the magnetar central-engine interpretation."],"supporting_citations":[{"why":"This work established the 2.058 micron He I line as a helium diagnostic that is less affected by blending in stripped-envelope supernovae.","marker":"Matheson et al. 2001"},{"why":"This work modeled stripped-envelope supernovae and showed that even a nearly bare CO core with about 0.1 solar masses of helium can yield a detectable 2.058 micron feature.","marker":"Hachinger et al. 2012"},{"why":"This work quantified that optical helium lines require large helium masses (roughly 0.2-1.0 solar masses), motivating the near-infrared search.","marker":"Teffs et al. 2020"},{"why":"This work supplied Type Ib and Ic near-infrared spectra and line identifications used to classify SN 2024ahr's near-infrared spectrum as Ic-like.","marker":"Shahbandeh et al. 2022"},{"why":"This work provided the spectral synthesis modeling setup that the paper adapts to translate its non-detection into a helium mass limit.","marker":"Williamson et al. 2021"},{"why":"This paper describes the spectral synthesis code used to compute the synthetic spectra with added helium masses.","marker":"Kerzendorf & Sim 2014"},{"why":"This work reported the only claimed He I 2.058 micron detection in an SLSN-I and provides the direct spectral comparison in Figure 4.","marker":"Yan et al. 2020"}],"fun_headline_variants":["No helium in SN 2024ahr hints at fully stripped progenitor","SN 2024ahr's near-IR spectrum finds no helium above 0.05 solar masses","Helium-free SN 2024ahr: a fully stripped massive star explosion","Typical SLSN-I SN 2024ahr shows no helium in its near-IR spectrum","Near-IR search reveals SN 2024ahr's outer ejecta is helium-free"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The upper limit rests on the assumption that $0.05\\,M_\\odot$ of helium placed in the outer ejecta of a model tuned to this supernova would actually produce a visible absorption feature at $2.058\\,\\mu\\mathrm{m}$; if the true helium line formation is weaker than the model predicts, or the model is not representative of such explosions at day 43, the limit would be too strict.","fun_headline_variants_meta":{"raw":{"variants":["No helium in SN 2024ahr hints at fully stripped progenitor","SN 2024ahr's near-IR spectrum finds no helium above 0.05 solar masses","Helium-free SN 2024ahr: a fully stripped massive star explosion","Typical SLSN-I SN 2024ahr shows no helium in its near-IR spectrum","Near-IR search reveals SN 2024ahr's outer ejecta is helium-free"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001004,"raw_usage":{"total_tokens":4368,"prompt_tokens":1191,"completion_tokens":3177,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":807,"completion_tokens_details":{"reasoning_tokens":3070}},"tokens_in":807,"tokens_out":3177,"duration_ms":22107,"temperature":1.0,"reasoning_tokens":3070,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-10T22:28:02.098017+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A later or deeper near-infrared spectrum of SN 2024ahr that reveals absorption at the blueshifted position of He I $\\lambda2.058\\,\\mu\\mathrm{m}$ would overturn the conclusion that the outer ejecta are helium-free. An independent spectral synthesis calculation showing that $0.05\\,M_\\odot$ of helium in the adopted ejecta produces no detectable absorption at that wavelength would invalidate the upper limit, since the limit is set by the predicted visibility of that feature.","supporting_citations":[],"review_version":1}