{"id":"c4fd7c95-aaab-4011-89cc-ba323d2d1f6c","arxiv_id":"2501.09663","paper_version":3,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"New 3D simulations show Rayleigh-Taylor instabilities turn jet-driven common-envelope ejecta into filaments, with faster envelope rotation making spiral arms more prominent.","lead":"Three-dimensional simulations show that when a neutron star spirals inside a red supergiant and launches jets, Rayleigh-Taylor instabilities carve the ejected gas into filaments and bubbles, and a rotating envelope makes the spiral pattern more pronounced. The result suggests a concrete mechanical explanation for the clumpy, jet-shaped outflows that might appear in some stellar transients.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Jet-injection region is only ~2 cells across at the resolution used for jetted runs; RTI maps may trace the numerical stencil rather than a physical instability, so the central claim needs a resolution/injection-geometry check.","rationale":"The central claim of the paper is that Rayleigh-Taylor instability forms the filamentary ejecta seen in simulations of jet-launching NSs inside a common envelope. For this claim to hold, the high-pressure regions that accelerate the envelope must be physically meaningful. The simulations impose the jet energy and momentum in a small cylindrical volume; at the only resolution used for jetted runs, this volume is only a few grid cells across. Thus the pressure field that the RTI analysis probes is locally dominated by the numerical stencil. The no-jet resolution comparison (Figure 1) does not validate the jetted runs, because the injection region itself is the feature that needs resolution. The RTI maps in Figure 9 are computed from the regular-resolution flow, so they may simply trace the boundary of the injection cylinder rather than a converged hydrodynamic instability. This concern is more specific than the reader's general point about the imposed geometry: it quantifies the mismatch and gives a concrete test. I do not think it requires rejecting the paper, because the qualitative large-scale morphologies (spiral arms, bubbles) may survive resolution changes, and the rotating-envelope results before jets are independent. But the paper's main causal statement is at risk, so conditional acceptance with a mandatory resolution/injection-geometry check is appropriate. Hence the verdict stays as the reader's CONDITIONAL.","tokens_in":13911,"tokens_out":6607,"duration_ms":70590,"concrete_test":"Run the α=0.5 jetted simulation at the high resolution (Δ=1.95×10^12 cm) to t≃3.8 yr and compare (i) the density maps in the planes of Figure 7, (ii) the f_st maps of Figure 9, and (iii) the power spectrum of density fluctuations in the ejecta against the regular-resolution run. In parallel, at regular resolution, rerun with a cylindrical injection region of doubled radius and height (same total energy/momentum) and check whether the filament sizes and the RT-unstable zone morphologies are invariant. If any of these comparisons show changes comparable to the filament size or the instability growth time, the RTI interpretation is an artifact of the injection stencil; if the qualitative structures and measured growth times remain unchanged, the concern is settled.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The most load-bearing weakness is that the jet-inflated high-pressure region that seeds the Rayleigh-Taylor instability is not numerically resolved. In Section 2 the jet-envelope interaction region is a cylinder of base radius 4×10^12 cm and height 14×10^12 cm; at the regular grid resolution used for all simulations with jets (Δ=3.90625×10^12 cm, Section 3), that cylinder spans only ~2 cells in radius and ~4 cells in height. The pressure gradients and density interfaces that Figure 9 diagnoses as RT-unstable are therefore determined by the injection stencil and the Cartesian grid, not by a converged hydrodynamical flow. The conclusion that RTI 'forms the filamentary ejecta' is an inference from correlation with these under-resolved zones (Section 4), and no jet simulation is run at the higher resolution used for the no-jet convergence check. This does not prove the claim wrong, but it makes the central conclusion unsupported until the effect of resolving the injection region is tested.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents three-dimensional FLASH simulations of a neutron star spiraling inside a red supergiant envelope and launching jets, with emphasis on the effect of pre-existing envelope rotation. The authors first study the rotating envelope without jets, finding non-radial oscillations and convection, which they use to argue that 1D stellar models need not be relaxed before mapping to 3D. They then inject jets via a prescribed cylindrical energy/momentum deposition region around the neutron star and analyze the resulting ejecta morphology. The central new claim is that Rayleigh-Taylor instability, diagnosed by the sign of the dot product of the pressure and density gradients, forms the observed filamentary and bubble structures in the ejecta, with and without envelope rotation, and that faster rotation makes the spiral pattern more prominent.","tokens_in":14104,"tokens_out":9093,"duration_ms":91726,"significance":"If the Rayleigh-Taylor interpretation is correct, the paper provides a physical mechanism for the clumpy, filamentary ejecta expected in CEJSN impostors and, more broadly, for jet-envelope interactions in common envelope evolution. The study has several strengths: it extends earlier 3D jet-in-CEE simulations to rotating envelopes; it includes explicit resolution comparisons for the no-jet phase (Figure 1) and a multi-resolution morphology check for the jet phase (Figure 8); and it clearly states its main simplifications (fixed NS orbit, no NS gravity, inert inner core, under-resolved injection region). The RTI diagnostic is parameter-free, being computed directly from simulation fields, and the paper makes falsifiable statements about spiral prominence versus rotation rate. However, as detailed below, the causal RTI claim currently rests on correlational evidence and on a jet-injection region that is barely resolved, so the central conclusion needs additional support before it can be regarded as established.","major_comments":[{"comment":"The jet-envelope interaction region is a cylinder with base radius 4×10^12 cm and height 14×10^12 cm (Section 2). At the regular resolution used for the fiducial jetted runs, Δ = 3.90625×10^12 cm (Section 3), that cylinder is only about 2 cells across in radius and about 4 cells in height; even the 'higher-resolution' jet run in Figure 8 uses a cell size of about 3.125×10^12 cm, leaving the radius at about 1.3 cells. The pressure and density gradients entering the RTI diagnostic f_st (Eq. 3, Fig. 9) are therefore determined by the injection stencil and Cartesian grid rather than by a converged hydrodynamic flow. No RTI map is shown for a run with the injection region resolved by several cells or with an alternative injection geometry. The central conclusion that RTI forms the filaments is not supported until such a test is performed.","section":"§2, §3, §4 (Figs. 8–9)"},{"comment":"The abstract and Section 5 state that RTI forms the filamentary ejecta 'with and without envelope rotation,' but the RTI maps in Figure 9 are shown only for α = 0.5. No f_st maps or growth-time estimates are presented for the α = 0.25 and α = 0 cases, even though the text asserts that these cases are also prone to RTI. To make the general claim, the authors should either provide the analogous RTI analysis for the other rotation cases or rephrase the conclusion to refer specifically to the α = 0.5 case.","section":"§4 (Fig. 9) and abstract"},{"comment":"The evidence that RTI causes the filaments is correlational: the paper shows that at two epochs the regions with f_st < 0 occupy the same areas as the filaments and that the nominal growth time (τ_RT ≈ 0.16 yr) is much shorter than the simulation duration (2.3–3.8 yr). This is necessary but not sufficient for the causal claim; the same maps could hold if the unstable zones are advected or stabilized. A stronger test would track unstable fluid parcels (e.g., with Lagrangian tracers) to see whether they grow into the observed density filaments, or would quantify the correlation between the initial unstable regions and the later density structure.","section":"§4 (after Eq. 3)"},{"comment":"The simulations omit the neutron star's gravity and prescribe the spiral-in orbit and the cylindrical jet-injection geometry. The high-pressure, low-density volumes that seed the RTI are therefore imposed by the injection scheme rather than arising from a self-consistent accretion flow. The authors acknowledge this simplification, but they do not assess how strongly the RTI conclusion depends on it. A sensitivity test that varies the injection cylinder dimensions or includes a Newtonian point mass for the NS would indicate whether the filamentary RTI pattern is robust or an artifact of the chosen prescription.","section":"§2 and §4"}],"minor_comments":[{"comment":"In Section 4 the text says 'we use only the regular resolution when including jets,' but Figure 8 and its caption describe jet simulations at three resolutions (labeled 0.714, 1, and 1.25); please clarify which runs were actually performed and why the earlier statement is retained.","section":"§4 and Fig. 8"},{"comment":"Section 1 contains the typo 'CEJSN importers' (should be 'CEJSN impostors'), and Section 2 has 'metalicity' instead of 'metallicity'.","section":"§1 and §2"},{"comment":"Equation (2) appears garbled in the typeset version ('ρ q − →∇P · − →∇ρ'); it should presumably read ρ / sqrt(|∇P · ∇ρ|). Please correct the rendering.","section":"Eq. (2)"},{"comment":"The notation for the stability frequency is inconsistent: the text uses f_st, Eq. (3) uses f_st, Figure 9's caption uses fST, and the color bar label is '1/yr'. Please unify the notation.","section":"§3 and Fig. 9"},{"comment":"The caption states that the higher-resolution run uses a grid that is 'smaller due to the small cell size'; it would help to give the actual grid size in physical units for each resolution, as is done for the regular and high resolutions in Section 3.","section":"Fig. 8"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The paper is a solid extension of the authors' earlier CEJSN impostor work. It adds pre-set envelope rotation and a Rayleigh-Taylor instability diagnostic. The new result that faster rotation makes the spiral ejecta more prominent is real and worth noting. The RTI maps show growth times around 0.16 years, far shorter than the simulation time, which supports the idea that the instability is active. The authors are also honest about their simplifications: no NS gravity, a prescribed orbit, and an inert inner 20% of the star.\n\nThe main soft spot is the resolution of the jet-injection region. The cylinder where jet energy is deposited has a base radius of 4e12 cm and height 14e12 cm. At the regular cell size of 3.90625e12 cm, that is only about two cells across. The higher-resolution jet run in Figure 8 improves this by only a factor of 1.25, still leaving the injection geometry under-resolved. Since the RTI maps are computed from the same under-resolved fields, the pressure gradients driving the instability could be numerical artifacts of the injection stencil rather than a physical flow. The causal link between RTI and filaments is inferred from correlation, not demonstrated by a direct perturbation analysis or a convergence check on the injection region.\n\nA related issue: the paper claims there is no need to relax 1D stellar models before 3D simulation, but their oscillations decay after two periods and are not driven by the same physics as real RSG pulsations. They acknowledge this, but the claim still feels overreached without a more quantitative comparison to observed RSG variability.\n\nThe paper ships no code or data, which is normal for this kind of study but does limit reproducibility. The reference list is appropriate, and the reliance on their own prior work is reasonable since this is a direct continuation.\n\nOverall, the rotation-spiral effect is a genuine new finding, and the RTI diagnostic is a useful way to look at the ejecta. But the central claim that RTI forms the filamentary ejecta needs a resolution/injection-geometry check before it can be taken as established. This is addressable, not fatal.\n\nI would send this to peer review with a request for major revision. A referee should ask for a jet run with the injection region resolved by several cells, or at least a test with a different injection geometry. The paper belongs in the CEE and jet-driven transient literature, and the rotation result is worth citing once the RTI claim is firmed up.","headline":"A credible extension of the authors' CEJSN impostor simulations, but the Rayleigh-Taylor filament claim is undercut by a jet-injection region that is only about two cells wide at the resolution used.","tokens_in":14681,"tokens_out":3111,"would_cite":false,"duration_ms":31995,"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":"Filamentary stellar ejecta traced to Rayleigh-Taylor instability","keywords":["common envelope evolution","neutron star jets","Rayleigh-Taylor instability","three-dimensional hydrodynamics","red supergiant envelope","CEJSN impostor","envelope rotation","filamentary ejecta"],"falsifier":"Run the fastest-rotating case again with the same total jet energy but deposited spherically instead of as two opposed cylindrical jets; if filaments of similar size still emerge, the Rayleigh-Taylor interpretation is supported, whereas if they disappear, the jet collimation is doing the shaping. A complementary check is to compare the widths of the dense filaments in the density maps with the fastest-growing Rayleigh-Taylor wavelength estimated from the $f_{\\rm st}$ maps; a clear mismatch in scaling would count against the conclusion.","tokens_in":13689,"feed_emoji":"🌀","tokens_out":14593,"duration_ms":120774,"temperature":0.7,"pith_summary":"The paper aims to show that the filamentary, bubble-filled ejecta produced when a neutron star launches jets while spiraling inside a red supergiant envelope are shaped by Rayleigh-Taylor instability, not by the jet geometry alone. It runs three-dimensional hydrodynamical simulations with three initial envelope rotation rates, up to a case where the equatorial centrifugal force is one quarter of gravity, and maps the envelope zones where the Rayleigh-Taylor growth time is about 0.16 to 0.8 years. The instability appears with and without rotation; rotation only makes the spiral pattern of the ejecta more prominent. The result gives observers a concrete reason to expect clumpy, filamentary ejecta in common-envelope-jets-supernova impostors, transients that mimic peculiar supernovae.","feed_headline":"Filamentary stellar ejecta traced to Rayleigh-Taylor instability","feed_subtitle":"Clumpy ejecta trace unstable pressure bubbles in a giant star's envelope; rotation only sharpens the spiral.","key_machinery":"The load-bearing object is the Rayleigh-Taylor stability frequency $f_{\\rm st} = (1/\\rho)\\sqrt{| -\\vec{\\nabla}P\\cdot\\vec{\\nabla}\\rho |}\\,\\mathrm{sgn}(-\\vec{\\nabla}P\\cdot\\vec{\\nabla}\\rho)$, evaluated on the simulation grid. Negative values mark zones where pressure and density gradients oppose one another, making $-1/f_{\\rm st}$ approximately the instability growth time; positive values approximate the Brunt–Väisälä frequency of stable stratification. The instability is seeded by the jet-inflated high-pressure cavity around the neutron star, so the shape and location of that cavity, set by the prescribed cylindrical jet-deposition region and fixed spiral orbit, control where $f_{\\rm st}$ becomes negative.","core_discovery":"Using the same numerical framework as their earlier non-rotating study, the authors place a 12.5 solar-mass red supergiant envelope on a three-dimensional grid, add solid-body rotation at three strengths, and then inject bipolar jets from a neutron star following a fixed three-year spiral-in orbit. The jets inflate high-pressure, low-density cavities around the neutron star; as these cavities accelerate the denser envelope, the pressure and density gradients oppose each other, the defining condition for Rayleigh-Taylor instability. Maps of the stability frequency $f_{\\rm st}$ identify unstable zones with growth times of about 0.16 and 0.8 years, well within the 2.3- to 3.8-year evolution shown in the density maps, and the authors interpret the dense filaments and low-density bubbles as the nonlinear outcome of these modes. Faster initial envelope rotation leaves the instability mechanism unchanged but makes the spiral structure of the ejecta more pronounced. Before the jets are switched on, the rotating envelope expands at the equator, contracts at the poles, oscillates non-radially for about two periods, and becomes convective, which the authors read as support for starting 3D common envelope simulations from unrelaxed one-dimensional stellar models.","pith_inferences":["Editorial inference: the characteristic size of the filaments should be set by the density scale height near the jet-inflated cavity, so varying the radius of the cylindrical injection region in controlled runs would test whether the filament spacing follows the cavity size or the intrinsic Rayleigh-Taylor wavelength.","Editorial inference: because the simulations omit the neutron star's gravity and accretion flow, the pressure distribution that seeds the instability is imposed; a simulation with an accreting point mass would show whether the same unstable zones survive when the gravitational well reshapes the cavity.","Editorial inference: if this mechanism operates, the clumpiness of a real common-envelope-jets-supernova impostor could be used as a probe of the red supergiant's density and pressure gradients at plunge-in, making high-cadence photometric and spectropolarimetric monitoring a test of the model."],"forward_implications":["Filaments and bubbles should be generic in jet-driven common envelope events: any jet-inflated cavity that accelerates denser envelope gas will seed Rayleigh-Taylor modes.","Envelope rotation is a secondary effect for mass ejection; simulations that ignore rotation should still capture the instability and the basic clumpy morphology, while studies of spiral structure must include rotation.","Synthetic light curves and spectra of common-envelope-jets-supernova impostors should be built from clumpy, filamentary ejecta rather than smooth spherical shells, since the density maps show structure on scales a few times smaller than the stellar radius.","Starting 3D common envelope simulations from unrelaxed one-dimensional giant-star models remains defensible, because the resulting oscillations and convection mimic real red supergiant behavior and decay within about two periods."],"supporting_citations":[{"why":"Supplies the non-rotating baseline, the numerical setup, the fixed spiral orbit, and the jet-deposition scheme that this paper extends to rotating envelopes.","marker":"Hillel, Schreier, & Soker (2023)"},{"why":"Provides the standard Rayleigh-Taylor growth-rate expression used to define the stability frequency and identify unstable envelope zones.","marker":"Priest (1982)"},{"why":"Provides the negative jet-feedback correction factor that sets the jet power from the Bondi-Hoyle-Lyttleton accretion rate.","marker":"Grichener, Cohen, & Soker (2021)"},{"why":"Reports the one-dimensional simulations of the negative feedback mechanism that motivate the small jet-power factor used here.","marker":"Hillel, Schreier, & Soker (2022)"},{"why":"Defines the common-envelope-jets-supernova scenario that the neutron-star-in-red-supergiant simulation is built to model.","marker":"Soker & Gilkis (2018)"},{"why":"Defines the common-envelope-jets-supernova impostor event class whose filamentary ejecta morphology this paper interprets.","marker":"Gilkis, Soker, & Kashi (2019)"},{"why":"Supplies the one-dimensional stellar evolution model used to construct the 12.5 solar-mass red supergiant envelope initial condition.","marker":"Paxton et al. (2011)"},{"why":"Supplies the three-dimensional hydrodynamics code used for all simulations.","marker":"Fryxell et al. (2000)"}],"fun_headline_variants":["Jets inflate bubbles that shred a giant's envelope into filaments","Rayleigh-Taylor instability sculpts clumpy ejecta in common envelope","Rotating envelopes sharpen spiral ejecta but not the instability","Neutron star jets trigger filaments via Rayleigh-Taylor in 3D","Filamentary ejecta from Rayleigh-Taylor during common envelope"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The jets are inserted through a fixed cylindrical injection region with the neutron star's gravity omitted and its spiral-in orbit prescribed in advance, so the high-pressure bubble that seeds the instability is set by the injection geometry rather than by self-consistent accretion physics.","fun_headline_variants_meta":{"raw":{"variants":["Jets inflate bubbles that shred a giant's envelope into filaments","Rayleigh-Taylor instability sculpts clumpy ejecta in common envelope","Rotating envelopes sharpen spiral ejecta but not the instability","Neutron star jets trigger filaments via Rayleigh-Taylor in 3D","Filamentary ejecta from Rayleigh-Taylor during common envelope"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000567,"raw_usage":{"total_tokens":2732,"prompt_tokens":1039,"completion_tokens":1693,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":655,"completion_tokens_details":{"reasoning_tokens":1602}},"tokens_in":655,"tokens_out":1693,"duration_ms":11408,"temperature":1.0,"reasoning_tokens":1602,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-10T19:47:35.664585+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the fastest-rotating case again with the same total jet energy but deposited spherically instead of as two opposed cylindrical jets; if filaments of similar size still emerge, the Rayleigh-Taylor interpretation is supported, whereas if they disappear, the jet collimation is doing the shaping. A complementary check is to compare the widths of the dense filaments in the density maps with the fastest-growing Rayleigh-Taylor wavelength estimated from the $f_{\\rm st}$ maps; a clear mismatch in scaling would count against the conclusion.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the non-rotating baseline, the numerical setup, the fixed spiral orbit, and the jet-deposition scheme that this paper extends to rotating envelopes."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the negative jet-feedback correction factor that sets the jet power from the Bondi-Hoyle-Lyttleton accretion rate."}],"review_version":1}