{"id":"320d8ffd-0e25-4c97-8b81-5f352acb88f8","arxiv_id":"2607.12525","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"SN 2020akf is classified as a transitional Type Ic and SN 2021mxx as a normal Type Ic with extremely low M_ej/E_k, from photometry, spectroscopy, and Arnett-model fits.","lead":"This paper reports optical light curves and spectra for two Type Ic supernovae, SN 2020akf and SN 2021mxx, and derives their luminosities, ejecta velocities, kinetic energies, ejected masses, and nickel yields. The results place one event as transitional between normal and broad-line Ic and the other as a normal Ic with an unusually low mass-to-energy ratio, enlarging the well-measured stripped-envelope sample.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"Abstract-only review leaves the Arnett-derived E_k and M_ej values unverifiable; the load-bearing premise cannot be stress-tested without light curves or model details.","rationale":"The Reader correctly identified the Arnett-model premise as the weakest assumption and correctly assigned UNVERDICTED / LOW confidence given that only the abstract is available. No additional internal inconsistency appears in the abstract numbers themselves; the Fe II velocities and peak luminosities are within the normal range for Type Ic events, and the quoted metallicities are incidental. The concern is therefore not that the numbers are obviously wrong, but that they cannot be verified or falsified without the light curves, spectra, and model details that the abstract omits. That is precisely the limitation the Reader already flagged, so the verdict remains UNVERDICTED and no adjustment is warranted.","tokens_in":2339,"tokens_out":615,"duration_ms":5292,"concrete_test":"Obtain the full paper (or the light-curve data and Arnett-fit code). Re-fit the quasi-bolometric light curves with the same Arnett formalism but with opacity varied over the conventional range κ = 0.05–0.2 cm^{2} g^{-1} and with both central and mixed 56Ni distributions. If the recovered M_ej or E_k for either SN shifts by more than the quoted 1-σ uncertainties, the headline parameter claims weaken.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central quantitative claims (E_k ≈ 6.33×10^51 erg, M_ej ≈ 4.71 M_☉ for SN 2020akf; E_k ≈ 0.54×10^51 erg, M_ej ≈ 0.90 M_☉ for SN 2021mxx) rest entirely on the semi-analytical Arnett model applied to quasi-bolometric light curves that are not shown. The abstract supplies only peak log L_bol and Fe II velocities; it does not report the rise time, diffusion timescale \tau_m, opacity assumption, or the exact fitting procedure that converts those observables into the quoted masses and energies. Without those intermediate quantities, it is impossible to check whether the reported M_ej/E_k ratios (especially the “extremely low” ratio for SN 2021mxx) are robust or are artifacts of the usual Arnett simplifications (constant opacity, centrally concentrated 56Ni, pure radioactive powering). The transitional/normal spectral classifications are likewise asserted without any line-width measurements, comparison spectra, or figures. Because the full text is unavailable, the single most load-bearing concern is simply that the abstract numbers cannot be independently reproduced or stress-tested.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript presents optical photometry and medium-resolution spectroscopy of two Type Ic supernovae, SN 2020akf (−5 to +109 d) and SN 2021mxx (−3 to +115 d) relative to B-band maximum. Peak quasi-bolometric luminosities are reported as log L_bol = 42.37 ± 0.02 and 42.21 ± 0.02 erg s−1. Fe II λ5169 velocities near maximum are ~15 000 km s−1 and ~10 000 km s−1. Applying the semi-analytical Arnett model, the authors derive E_k ≈ 6.33 × 10^51 erg, M_ej ≈ 4.71 M_⊙, M_Ni ≈ 0.10 M_⊙ for SN 2020akf and E_k ≈ 0.54 × 10^51 erg, M_ej ≈ 0.90 M_⊙, M_Ni ≈ 0.05 M_⊙ for SN 2021mxx. Host metallicities near the SN sites are ~0.81 and ~0.76 Z_⊙. They classify SN 2020akf as a transitional Ic (between normal and broad-line) and SN 2021mxx as a normal Ic with an extremely low M_ej/E_k ratio.","tokens_in":2653,"tokens_out":1300,"duration_ms":19826,"significance":"Well-sampled light curves and spectra of stripped-envelope SNe remain valuable for expanding the Type Ic parameter space. If the Arnett-derived parameters and the transitional classification hold under full scrutiny, SN 2020akf would help populate the intermediate region between normal and broad-line Ic events, while an extremely low M_ej/E_k for SN 2021mxx would be a useful constraint for explosion and progenitor models. Host-metallicity estimates near the explosion sites are a standard but useful addition for progenitor-environment studies. The work is incremental rather than transformative, but of clear interest to the SN community if the reductions, fits, and classifications are robust.","major_comments":[{"comment":"The central quantitative results (E_k, M_ej, M_Ni for both events) rest on the semi-analytical Arnett model applied to quasi-bolometric light curves. The abstract quotes only peak log L_bol and Fe II velocities; it does not report rise time, diffusion timescale τ_m, adopted opacity, nickel distribution, or the fitting procedure that converts those observables into the stated masses and energies. Without those intermediate quantities and the light curves themselves, the reported values—especially the “extremely low” M_ej/E_k for SN 2021mxx—cannot be independently checked for sensitivity to the usual Arnett assumptions (constant opacity, spherical homologous expansion, centrally concentrated 56Ni, pure radioactive powering). This is load-bearing for the paper’s main physical claims.","section":null},{"comment":"Classification of SN 2020akf as transitional between normal and broad-line Type Ic, and of SN 2021mxx as normal Ic, is asserted from spectral properties. Only Fe II λ5169 velocities at maximum (~15 000 and ~10 000 km s−1) are given. Line-width measurements at multiple epochs, comparison spectra, and the quantitative criteria used to place 2020akf in the transitional category are not available in the abstract and must be shown and justified in the full analysis; otherwise the classification claim is not verifiable.","section":null},{"comment":"The statement that SN 2021mxx has an “extremely low” M_ej/E_k ratio is a headline result. With M_ej ≈ 0.90 M_⊙ and E_k ≈ 0.54 × 10^51 erg the ratio is low relative to many published Ic samples, but its robustness depends on the same Arnett inputs and on how the quasi-bolometric light curve was constructed (filter coverage, bolometric corrections, distance/reddening). The manuscript must demonstrate that the low ratio survives reasonable variations in opacity, rise-time, and bolometric correction, and should place the ratio in a clearly defined comparison sample with consistent methodology.","section":null}],"minor_comments":[{"comment":"Abstract: units and spacing are inconsistent in places (e.g., “0.90 (+0.14)(-0.18),M_sun” with a stray comma; “SN~2020akf” TeX-style tildes). Clean for journal style.","section":null},{"comment":"Abstract: “the velocities of the ejecta, derived from the Fe II 5169 A line” — specify whether this is the absorption minimum at maximum light only or a time series, and whether other lines (e.g., O I, Ca II) were checked for consistency.","section":null},{"comment":"Host metallicities are given as ~0.81 and ~0.76 Z_⊙ “near the SN regions.” The full text should state the diagnostic (e.g., which strong-line method), aperture, and uncertainty, and whether the values are local or galaxy-averaged.","section":null},{"comment":"Error bars on E_k and M_ej are asymmetric and relatively tight. The full analysis should clarify whether these are statistical only or include systematic contributions from opacity, distance, and reddening.","section":null}],"recommendation":"uncertain","confidential_remarks":"Only the abstract was available for this review (full text not provided). I therefore cannot inspect photometry reductions, spectral figures, bolometric construction, or the actual Arnett fits. My recommendation is “uncertain” for that reason: the claims as stated are conventional and potentially publishable, but the load-bearing Arnett parameters and spectral classifications cannot be stress-tested without the full manuscript. Once the full text is in hand, a normal major/minor revision cycle should be feasible if the intermediate quantities and figures support the abstract numbers. Scope appears appropriate for an observational SN journal."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"This is a straightforward observational paper that adds two well-followed Type Ic supernovae, SN 2020akf and SN 2021mxx, with photometry and medium-resolution spectra spanning roughly -5 to +110 days. The new material is the light curves, the Fe II velocities (~15 000 and ~10 000 km/s), the quasi-bolometric peaks, and the Arnett-derived explosion parameters (E_k, M_ej, M_Ni) for these specific objects. That is honest progress: the stripped-envelope sample is still small enough that every carefully reduced event helps constrain progenitors and engines.\n\nWhat they do well, on the evidence of the abstract, is the conventional pipeline. Peak luminosities are given with realistic errors, host metallicities near the sites are reported, and the classifications (transitional Ic for 2020akf, normal Ic with a notably low M_ej/E_k for 2021mxx) are stated in the language of the existing literature. No new technique is claimed, and none is needed; the value is the data plus the derived numbers.\n\nThe soft spot is exactly the one the stress-test flags, and it is real but ordinary. All the load-bearing masses and energies come from the semi-analytical Arnett model applied to light curves we cannot see. Without rise times, diffusion timescales, opacity assumptions, or the actual fits, we cannot verify whether the “extremely low” M_ej/E_k for 2021mxx is robust or an artifact of the usual simplifications (constant opacity, central nickel, pure radioactive powering). The transitional/normal spectral claims likewise rest on unshown line widths and comparison spectra. That is the standard limitation of an abstract-only read, not evidence of circularity or invention. The free parameters are the usual Arnett ones; nothing looks fabricated.\n\nWho it is for: people who work on stripped-envelope SNe and need more objects with published parameters for population studies. A serious referee should see the full reductions, the bolometric construction, and the Arnett fits. I would send it to peer review; it is the kind of paper that, once the figures and tables are checked, belongs in the literature. I would not rush it into a reading group until the full text is available, and I would cite the parameters only after verifying the fits, but the work itself looks like clear, honest observational astronomy.","headline":"Solid observational addition of two Type Ic events with standard Arnett parameters; abstract-only so the numbers cannot be checked, but the work is the usual useful sample-building paper.","tokens_in":3304,"tokens_out":602,"would_cite":false,"duration_ms":5986,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Two Type Ic supernovae yield ejecta masses and energies that place one as transitional and the other as unusually low-ratio normal.","keywords":["Type Ic supernovae","SN 2020akf","SN 2021mxx","Arnett model","ejected mass","kinetic energy","nickel mass","stripped-envelope supernovae"],"falsifier":"Independent hydrodynamic modelling or late-time nebular spectroscopy that yields ejected masses or kinetic energies inconsistent with the Arnett-derived values for either supernova would falsify the reported parameters.","tokens_in":3261,"feed_emoji":"⭐","tokens_out":909,"duration_ms":6809,"temperature":0.7,"pith_summary":"The paper reports multi-epoch optical photometry and spectroscopy of two Type Ic supernovae, SN 2020akf and SN 2021mxx, spanning roughly five days before to more than 100 days after B-band maximum. From the light curves and spectra the authors construct quasi-bolometric luminosities, measure Fe II ejecta velocities, and fit a semi-analytical Arnett model to recover kinetic energy, ejected mass and nickel-56 mass for each event. SN 2020akf emerges with higher energy and mass and with spectral features intermediate between ordinary and broad-line Type Ic events, while SN 2021mxx is a normal Type Ic with an extremely low ejected-mass-to-kinetic-energy ratio. Host metallicities near both sites are sub-solar. The results enlarge the observed parameter space of stripped-envelope core-collapse explosions and supply concrete numbers that can be compared with other members of the class.","feed_headline":"Two Type Ic supernovae: one transitional, one with extreme low mass-energy ratio","feed_subtitle":"Arnett fits give concrete ejecta masses and energies that widen the known range of stripped-envelope explosions","key_machinery":"The semi-analytical Arnett model, which assumes constant opacity, spherical homologous expansion, centrally concentrated 56Ni and pure radioactive powering, is fitted to the quasi-bolometric light curves to convert observed luminosity and velocity into estimates of ejected mass, kinetic energy and nickel mass.","core_discovery":"SN 2020akf is a transitional Type Ic supernova whose spectral properties sit between normal and broad-line Type Ic events, while SN 2021mxx is a normal Type Ic supernova distinguished by an extremely low M_ej/E_k ratio; the Arnett-model parameters are E_k ≈ 6.33 × 10^51 erg, M_ej ≈ 4.71 M_☉, M_Ni ≈ 0.10 M_☉ for 2020akf and E_k ≈ 0.54 × 10^51 erg, M_ej ≈ 0.90 M_☉, M_Ni ≈ 0.05 M_☉ for 2021mxx.","pith_inferences":["The low M_ej/E_k of SN 2021mxx may point to a low-mass progenitor or highly asymmetric mass ejection that the spherical Arnett model underestimates.","If transitional objects like SN 2020akf are common, the boundary between normal and broad-line Type Ic supernovae may be continuous rather than discrete.","Future multi-wavelength coverage of similar events could test whether the optical quasi-bolometric luminosity undercounts the true energy budget."],"forward_implications":["SN 2020akf enlarges the sample of transitional Type Ic events that bridge normal and broad-line spectral classes.","SN 2021mxx demonstrates that normal Type Ic explosions can reach unusually low M_ej/E_k ratios, expanding the observed range of explosion parameters.","The derived nickel masses (0.10 and 0.05 solar masses) provide benchmarks for nucleosynthesis yields in stripped-envelope core-collapse models.","Host metallicities near 0.8 solar supply environmental context for progenitor channels of both objects."],"fun_headline_variants":["SN 2020akf: transitional Type Ic between normal and broad-line","SN 2021mxx shows normal Type Ic with extreme low M_ej/E_k","Arnett model: 2020akf ejects 4.71 M_sun at 6.33e51 erg","Two Ic SNe: high-energy transitional vs low-mass-energy normal","Fe II speeds 15k and 10k km/s frame Ic pair with Ni-56 yields"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The Arnett model with its simplifying assumptions of constant opacity, spherical symmetry and centrally concentrated radioactive nickel correctly recovers the true ejected mass and kinetic energy from the light curves.","fun_headline_variants_meta":{"raw":{"variants":["SN 2020akf: transitional Type Ic between normal and broad-line","SN 2021mxx shows normal Type Ic with extreme low M_ej/E_k","Arnett model: 2020akf ejects 4.71 M_sun at 6.33e51 erg","Two Ic SNe: high-energy transitional vs low-mass-energy normal","Fe II speeds 15k and 10k km/s frame Ic pair with Ni-56 yields"]},"model":"grok-4.5","effort":"low","cost_usd":0.005214,"raw_usage":{"total_tokens":1639,"prompt_tokens":1107,"num_sources_used":0,"completion_tokens":127,"cost_in_usd_ticks":52140000,"prompt_tokens_details":{"text_tokens":1107,"audio_tokens":0,"image_tokens":0,"cached_tokens":128},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":405,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":1107,"tokens_out":127,"duration_ms":3545,"temperature":1.0,"reasoning_tokens":405,"cache_read_input_tokens":128,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-15T05:24:39.174270+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"Independent hydrodynamic modelling or late-time nebular spectroscopy that yields ejected masses or kinetic energies inconsistent with the Arnett-derived values for either supernova would falsify the reported parameters.","supporting_citations":[],"review_version":1}