{"id":"075c78a6-8747-4db7-b197-0f72eb99b0b7","arxiv_id":"2412.09893","paper_version":2,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"Late mass transfer from a helium star to a main-sequence companion can shed up to 0.8 solar masses of helium-rich gas, forming a circumstellar disk like those inferred for Type Ibn supernovae, and may explain about 10 percent of stripped-envelope supernovae.","lead":"Using binary evolution models, this paper shows that a helium star can transfer up to 0.8 solar masses of hydrogen-free gas to a companion in the last 20,000 years before exploding as a supernova. If that gas forms a disk around the binary, the supernova's ejecta would crash into it, producing the interacting hydrogen-poor supernovae astronomers see as Type Ibn events.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Case B stability criterion is the load-bearing uncertainty: under Marchant (2017), the rerun qi=0.5 systems merge and the ~12% rate collapses.","rationale":"The paper develops a plausible binary channel for Type Ibn/Icn progenitors and supports it with a dedicated grid of MESA models, including reruns that follow the donor to near core collapse. The qualitative match to observed MCSM, Mej and RCSM is conditional on the CSM forming a circumbinary disk, an assumption the authors state clearly and do not overclaim; they call for future models of the disk evolution. The rate claim, however, is the quantitative headline and is not protected by such a caveat. It depends critically on the survival of the binary through the earlier Case B RLOF. The rerun grid is restricted to qi = 0.5, and Sect. 7.2.2 shows that under the Marchant (2017) radiation-driven-ejection criterion every one of these systems would be unstable and merge, removing the channel entirely for the computed models. The alternative Pauli (2020) criterion leaves most of them stable, but the paper provides no decisive argument for preferring it; it only documents the difference. The population estimate in Sect. 5.6 filters unstable systems using the grid's Sect. 2.4 criteria, none of which correspond to the Marchant limit, so the ~12% figure is not robust to this unresolved choice. A straightforward recomputation with the Marchant filter would settle the issue. I therefore agree with the reader's assessment that this is the weakest assumption. The authors should be credited for flagging this sensitivity in Sect. 7.2.2, but because they do not resolve it or recompute the rate, the central claim remains conditional. No other concern appears as load-bearing: the CSM geometry is explicitly modeled as a scenario, the nuclear network is a known approximation with literature support, and the wind prescriptions are discussed with appropriate uncertainty. The verdict CONDITIONAL with high confidence is appropriate.","tokens_in":47840,"tokens_out":6764,"duration_ms":67453,"concrete_test":"Recompute the Sect. 5.6 population synthesis after excluding all binaries in the Jin et al. grid that the Marchant (2017) criterion (Eq. 5) flags as unstable during Case B RLOF, using the single-hatched region of Fig. 16 or applying Eq. 5 model by model. If the resulting fraction of stripped-envelope SNe from Case BC RLOF falls below ~1%, the central rate claim hinges on an unresolved stability choice. As a secondary check, verify whether any systems with qi >= 0.7 survive, since those are the ones Marchant allows for M1,i = 12.6 Msun.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central quantitative claim is the ~12% of stripped-envelope SNe from Case BC RLOF (Sect. 5.6; abstract), matching the observed ~9.2% Type Ibn fraction (Perley et al. 2020). This rate assumes the binaries survive the earlier Case B RLOF. All rerun models adopt qi = 0.5 (Sect. 3.3), and the population estimate extrapolates from these to the full grid. The stability of Case B RLOF is unresolved. In Sect. 7.2.2 the authors show that the Marchant (2017) criterion (Eq. 5) flags all qi = 0.5 rerun models as unstable: during Case B the donor temporarily dims, and the combined luminosity cannot eject unaccreted material, so the system enters a common envelope and merges (Fig. 16). The Pauli (2020) criterion is less stringent and leaves most of the rerun models stable, but the authors do not establish which criterion is correct; they only state that 'applying different mass transfer stability criteria to the same 1D simulations significantly alters the predicted outcome' (Sect. 7.2.2). The population synthesis in Sect. 5.6 filters unstable RLOF using the grid's Sect. 2.4 criteria, which do not include the Marchant limit. Hence the 12% figure does not account for the possibility that most of the parameter space is removed. If the Marchant criterion holds, the rerun models are not valid progenitors and the rate should be recomputed; based on Fig. 16 the fraction would drop dramatically, likely eliminating the claimed agreement with Perley et al. (2020). This is not an external disagreement but an internal sensitivity the authors themselves flag without resolving.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper proposes that H-free (helium-star) donors in close binaries with main-sequence companions can undergo a late phase of Roche-lobe overflow (Case BC RLOF) within ~20 kyr of core collapse, ejecting up to ~0.8 Msun of H-free material that forms a circumbinary disk. The authors argue that this channel can explain the inferred CSM masses, radii, ejecta masses, and light-curve morphologies of many Type Ibn SNe and some Type Icn SNe, and that population synthesis of a large binary grid yields about 10-12% of stripped-envelope SNe from this channel, matching the observed Type Ibn fraction of ~9.2%. The paper is based on 44 rerun binary models with improved physics and a mapping method to estimate Case BC RLOF properties across the full grid.","tokens_in":48240,"tokens_out":4401,"duration_ms":47235,"significance":"If the channel is robust, this would identify a specific, quantitative binary progenitor for a class of interacting H-poor supernovae, connecting binary evolution models to observed transients and providing a testable rate. The manuscript is strong in several respects: the binary evolution calculations are detailed and the authors transparently discuss uncertainties; the mapping method in Sect. 5.1 and Appendix B is a practical tool for extrapolating from rerun models to a large grid; and the comparison with observed MCSM, Mej, and RCSM in Sect. 6 is systematic and clearly presented. The paper also explicitly flags its own limitations, including the unresolved mass-transfer stability criterion and the numerical origin of Case X RLOF, which is commendable but also means the central quantitative claims are less secure than the abstract suggests.","major_comments":[{"comment":"The central rate claim (up to ~12% of stripped-envelope SNe, Sect. 5.6 and Conclusions) is contingent on the stability of Case B RLOF, which the authors themselves show is unresolved. In Sect. 7.2.2, the Marchant (2017) criterion (Eq. 5) is applied to the rerun models with qi = 0.5, and all of them are flagged as unstable during Case B RLOF (Fig. 16), implying merger rather than survival to Case BC RLOF. The less stringent Pauli (2020) criterion leaves most of the rerun models stable, but the manuscript does not establish which criterion is correct. The population synthesis in Sect. 5.6 uses the grid's stability criteria from Sect. 2.4, which do not include the Marchant limit, so the reported rate does not account for the possibility that most of the parameter space is removed. This is a load-bearing issue: the 12% figure and the claimed agreement with the observed ~9.2% Type Ibn fraction would collapse if the Marchant criterion holds. I request a quantitative exploration of this dependence, e.g., recomputing the rate under the Marchant criterion or providing a compelling argument for why the Pauli criterion is preferred.","section":"Sect. 7.2.2 and Sect. 5.6"},{"comment":"Half of the rerun models undergo Case X RLOF and fail to reach core collapse, and the manuscript states that the small-scale over/undershooting of 0.008 H_P introduced after core C burning is the direct cause of this behavior (Sect. 7.3.2), noting that these numerical settings 'lack physical backing' and were introduced for convergence. While the paper excludes the effect of Case X on the SN properties by using data at 1 yr before termination (Sect. 4.3), this does not resolve the physical fate of those systems: if Case X RLOF is a numerical artifact, the affected models would likely evolve differently and not explode with the proposed CSM structure; if it is real, the explosion during CE evolution would produce qualitatively different observational signatures. Since half of the rerun models are affected, this uncertainty propagates to the population estimate and the comparison with observed SNe. The paper should quantify how the exclusion or reclassification of Case X models affects the rate (Sect. 5.6) and the MCSM-Mej distributions (Fig. 11).","section":"Sect. 4.2.3 and Sect. 7.3.2"},{"comment":"The claimed qualitative agreement with Type Ibn light curves is based on a simplified model in which the CBD parameters (half-opening angle θ, density slope s, inner and outer radii, and explosion energy Ekin) are freely chosen. The manuscript itself describes this as 'very crude' and notes that radiation transport is neglected (Sect. 5.5). As a proof of concept this is acceptable, but the paper's abstract and conclusions present the light-curve morphology match as supporting evidence for the channel. Since the parameter space is large, the current analysis does not demonstrate that the models make distinctive, falsifiable predictions beyond what a generic disk-like CSM with adjustable parameters would produce. I recommend either reframing the light-curve comparison explicitly as an existence proof, or providing a more systematic exploration showing what range of θ, s, and Rin-Rout is required to match the observed Type Ibn sample and which observed events cannot be accommodated under any plausible choices.","section":"Sect. 5.5 and Fig. 13"}],"minor_comments":[{"comment":"The abstract states 'up to ~10%' of stripped-envelope SNe while Sect. 5.6 and the Conclusions state ~12%; please make these numbers consistent and report the uncertainty or range.","section":"Abstract and Sect. 5.6"},{"comment":"There are several typographical errors, including 'particularily' (Sects. 4.2.1 and 5.5), 'sorrunding' (Sect. 6.1), 'mash' for 'match' (Sect. 5.5), and '6end' in Table 1 note. A careful proofreading pass is needed.","section":"General"},{"comment":"The notation fM is used both for the mass fraction in Eq. (2) and for the angle-dependent fraction in Eq. (4) with different definitions; please disambiguate these symbols to avoid confusion.","section":"Sect. 5.3"},{"comment":"The bar chart of spatial distributions is dense and difficult to read, especially the overlapping hatched regions; consider presenting the key radii and masses in a table or in separate panels for clarity.","section":"Fig. 12"},{"comment":"The phrase 'in logarithmic steps of 0.01' for initial mass is ambiguous; please specify whether the step is 0.01 dex or 0.01 Msun.","section":"Sect. 3.3"}],"recommendation":"major_revision","confidential_remarks":"This is a well-executed and transparent study, but the central quantitative claim (the ~10-12% rate) rests on a stability criterion that the authors themselves show is unresolved. The paper would be considerably stronger if the rate were presented conditionally on the adopted stability criterion, or if the Marchant-criterion scenario were quantified. The Case X RLOF issue similarly undermines confidence in the affected models, though the paper's honesty about this is a positive sign. I encourage the editor to send the manuscript back for revision rather than rejecting it: the proposed channel is novel and the observational comparison is valuable, but the current wording of the abstract and conclusions overstates the robustness of the rate."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The paper's real content is a systematic binary grid mapping when post-He depletion mass transfer (Case BC RLOF) produces H-poor CSM around helium stars with main-sequence companions. That channel has been discussed for compact-object companions (WF22) and one tight system (Habets), but the systematic treatment for the HeS+MS configuration is new. The models are detailed and the authors are unusually candid: they flag that half their reruns fail before core collapse via Case X RLOF, that the overshooting which drives that phase is numerically motivated, and that the circumbinary disk geometry that makes the Type Ibn agreement work is assumed rather than modeled. The comparison with observed Ibn/Icn samples is diligent.\n\nThe central rate claim — up to ~12% of stripped-envelope SNe, matching the ~9.2% Ibn fraction — is the softest part. The population estimate assumes the rerun qi=0.5 systems survive the earlier Case B RLOF. Under the Marchant (2017) stability criterion, which the authors themselves show in Fig. 16, all those rerun models are unstable and would merge; the channel collapses. The Pauli (2020) criterion leaves them stable, but the paper does not resolve which criterion is physical. That is not an external attack — it is an internal sensitivity the authors flag without resolving. The 12% figure should not be presented as a quantitative match until this is settled.\n\nTwo smaller gaps: the CSM mass is an upper limit (some escapes), and the light-curve models are crude — no radiative transfer, and interaction-only power with a freely chosen disk half-opening angle and density slope. The qualitative shapes are suggestive, not proof.\n\nStill, the channel is physically plausible and the underlying binary evolution is independent of the observed SNe, so there is no circular fitting. The paper deserves serious referee time. I'd recommend sending it out, with the expectation that the authors either justify the Pauli criterion or explicitly present the rate as conditional on it, and ideally recompute the population estimate under the Marchant case as an upper/lower bound.","headline":"Plausible new binary channel for Type Ibn SNe, but the headline rate rests on an unresolved mass-transfer stability criterion.","tokens_in":48788,"tokens_out":1934,"would_cite":true,"duration_ms":21515,"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 a second phase of mass transfer in helium-star/main-sequence binaries, starting less than about 20,000 years before core collapse, can eject up to 0.8 solar masses of hydrogen-free material that forms a circumbinary…","keywords":["binary evolution","Case BC mass transfer","helium stars","Type Ibn supernovae","circumstellar material","circumbinary disk","stripped-envelope supernovae"],"falsifier":"A converged binary evolution model of a qi = 0.5, 12-14 solar-mass binary that applies the Marchant (2017) radiation-driven ejection limit and finds the system merges during Case B RLOF would falsify the channel and its ~10-12% rate prediction, because all the rerun models in this paper would then be unstable.","tokens_in":47638,"feed_emoji":"💥","tokens_out":7264,"duration_ms":70264,"temperature":0.7,"pith_summary":"This paper proposes a specific binary path for making the circumstellar shells seen around a class of hydrogen-poor supernovae. In a binary where a stripped helium star orbits a main-sequence companion, the helium star can swell in its final tens of thousands of years and dump up to 0.8 solar masses of helium-rich material toward the companion. If that material settles into a circumbinary disk, the supernova ejecta would hit the disk and shine like a Type Ibn supernova, with the masses, radii, and light-curve shapes inferred for many observed events. Combining the binary grid with a population calculation, the authors estimate that about 10 to 12 percent of stripped-envelope supernovae could come from this channel, matching the observed Type Ibn fraction.","feed_headline":"Late binary mass loss can build Type Ibn supernova shells","feed_subtitle":"A helium-star binary channel producing hydrogen-free shells could match the observed ~9 percent Type Ibn rate.","key_machinery":"The load-bearing mechanism is Case BC RLOF: a second phase of Roche-lobe overflow that begins after core helium exhaustion, when the stripped helium star (a HeS with mass below ~3.4 M_sun) expands by 1-2 orders of magnitude in radius within a few thousand years. The mass lost in this phase is clocked by how early the star starts filling its Roche lobe; the paper maps that duration to the transferred mass (about 0.8 M_sun if overflow begins 20 kyr before collapse). The companion accretes almost nothing, so the unaccreted helium-rich gas is lost from the binary, and, if it is ejected through the outer Lagrangian point, it settles into a circumbinary disk whose inner radius is a few times the binary separation. A simple momentum-conserving collision model between the supernova ejecta and this disk, with a density profile and half-opening angle, yields the interaction luminosity that shapes the light curve.","core_discovery":"The central discovery is that low-mass helium stars (below about 3.4 solar masses at core helium exhaustion) expand dramatically in the last ~20,000 years before core collapse, and in a binary this expansion can restart Roche-lobe overflow (Case BC mass transfer) onto a main-sequence companion. The donor loses 0.1 to 0.8 solar masses of hydrogen-free material, almost all of which escapes the binary because the companion is already spinning at critical rotation. If this material forms a bound circumbinary disk, a simple inelastic-collision model shows that the ejecta of the exploding donor convert up to tens of percent of their kinetic energy into radiation, reproducing the circumstellar masses, ejecta masses, CSM radii, and bell-shaped light curves inferred for many Type Ibn supernovae and a few Type Icn events. Mapping the mass-loss onto a full binary grid and weighting by the initial mass function gives up to ~12% of stripped-envelope supernovae from this channel, in line with the observed ~9.2% Type Ibn fraction.","pith_inferences":["If the disk geometry is confirmed by spectropolarimetry or line-profile modeling of Type Ibn SNe, the channel would simultaneously explain their light curves and their uncommon narrow-line persistence, which spherical CSM models struggle to reproduce.","The rate estimate depends on the adopted Case B stability criterion; settling that criterion observationally (e.g., through the number of Be-star secondaries near stripped stars) would sharpen the prediction.","A direct extension would be to compute spectral synthesis of these exploding donors with the CBD included; the paper leaves that to future work, but it is the decisive next test.","The same mass-transfer clock should apply to Type Icn/Ic-CSM SNe with Mej < 1.5 M_sun, since those also fall in the model parameter space, implying a continuum between Ibn and some Icn events from one binary channel."],"forward_implications":["Type Ibn supernovae with low ejecta mass and high CSM mass (Mej ~ 1 M_sun, MCSM 0.1-1 M_sun) are plausibly the explosions of these Case BC binaries rather than of single stars.","The CSM around many interacting H-poor SNe is expected to be disk-like rather than spherical, with interaction delayed by hours to about a day as the ejecta reach the inner disk edge.","About one in ten stripped-envelope supernovae should show interaction features of the kind the channel predicts, matching the observed Type Ibn fraction.","Systems that start mass transfer earlier strip more mass: 20 kyr before collapse gives ~0.8 M_sun of CSM, while 1 kyr gives ~0.1 M_sun, producing a spread in interaction strength.","The surviving binaries after the supernova should often be Be X-ray binaries or, later, merged neutron-star/white-dwarf pairs, a testable population prediction."],"supporting_citations":[{"why":"Establishes the late mass-transfer behavior of low-mass helium stars and the corresponding CSM, which this paper extends to helium-star plus main-sequence binaries.","marker":"WF22"},{"why":"Supplies the observed ~9.2% Type Ibn fraction that the population calculation must match.","marker":"Perley et al. (2020)"},{"why":"Shows that a large fraction of mass ejected through the outer Lagrangian point remains bound in a circumbinary disk, justifying the disk assumption.","marker":"Pejcha et al. (2016)"},{"why":"Provides the analytic CBD size and photoevaporation limits used to bound the disk extension.","marker":"Tuna & Metzger (2023)"},{"why":"Discusses mass ejection from the outer Lagrangian point and the threshold rate for disk formation, motivating the CBD scenario.","marker":"Lu et al. (2023)"},{"why":"Provides the stricter mass-transfer stability criterion that, if adopted, would remove the channel; the paper explicitly weighs it.","marker":"Marchant (2017)"},{"why":"Provides the adopted stability criterion under which the rerun binaries remain bound.","marker":"Pauli et al. (2022)"},{"why":"Supplies the comprehensive binary grid used to map the population and derive the ~12% rate.","marker":"Jin et al. (in prep.)"}],"fun_headline_variants":["Helium stars shed mass late, igniting Type Ibn supernovae","Binary helium stars build supernova shells before explosion","Expanding helium stars trigger late mass transfer in binaries","Late binary mass loss fuels hydrogen-free supernova shells"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The rate claim stands on the assumption that the first mass-transfer phase (Case B RLOF) leaves the binary bound; the paper adopts a stability criterion (Pauli et al.) under which the rerun binaries survive, whereas the stricter Marchant (2017) criterion would make all of the qi = 0.5 rerun models merge and remove the channel entirely.","fun_headline_variants_meta":{"raw":{"variants":["Helium stars shed mass late, igniting Type Ibn supernovae","Binary helium stars build supernova shells before explosion","Expanding helium stars trigger late mass transfer in binaries","Late binary mass loss fuels hydrogen-free supernova shells"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00105,"raw_usage":{"total_tokens":4492,"prompt_tokens":1109,"completion_tokens":3383,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":725,"completion_tokens_details":{"reasoning_tokens":3317}},"tokens_in":725,"tokens_out":3383,"duration_ms":26574,"temperature":1.0,"reasoning_tokens":3317,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T16:36:51.163276+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A converged binary evolution model of a qi = 0.5, 12-14 solar-mass binary that applies the Marchant (2017) radiation-driven ejection limit and finds the system merges during Case B RLOF would falsify the channel and its ~10-12% rate prediction, because all the rerun models in this paper would then be unstable.","supporting_citations":[{"cited_title":"D., & Tomida , K","cited_arxiv_id":null,"evidence_quote":"Shows that a large fraction of mass ejected through the outer Lagrangian point remains bound in a circumbinary disk, justifying the disk assumption."},{"cited_title":"& Metzger , B","cited_arxiv_id":null,"evidence_quote":"Provides the analytic CBD size and photoevaporation limits used to bound the disk extension."}],"review_version":1}