REVIEW 3 major objections 6 minor 2 cited by
Three-dimensional simulations of accretion disks in pre-CE systems
T0 review · 3 major / 6 minor · reviewed 2026-08-09 · deepseek-v4-flash
Pith's one-line read A 3D simulation predicts that just before a red supergiant and neutron star enter a common envelope, the neutron star hosts an accretion disk of about 0.005 solar masses, about 40 solar radii across, accreting at about 0.004 solar masses…
desk verdict Solid 3D pre-CE disk simulation, but the factor-of-few mass claim is hostage to the fixed gamma=1.1 no-cooling thermodynamics; deserves review but needs that caveat front and center. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The machinery is a compact-object-centred, co-rotating 3D hydrodynamic simulation with an L1 mass-injection nozzle: gas enters through a small elliptical nozzle at a rate interpolated from a 1D stellar evolution calculation covering 30,000 years, while a low-density background surrounds a spherical inner boundary at $1.3\,R_\odot$. The equation of state is quasi-isothermal with $\gamma=1.1$, chosen because earlier work found that RLOF and CE disks form only for $\gamma\lesssim1.2$; no self-gravity, magnetic fields, or explicit cooling are included. Disk radius is defined operationally as the first inflection point of the cumulative enclosed-mass profile, vertical density profiles define the scale height, and a specific-energy versus specific-angular-momentum diagram is used to show that the dense disk gas is bound and moving on low-eccentricity orbits.
What would settle it
Run the same binary through a 3D simulation with explicit radiative cooling and a realistic depth-dependent adiabatic index out to the onset of the common envelope: if the disk mass falls outside roughly $1.5\times10^{-3}$ to $1.5\times10^{-2}\,M_\odot$ or the radius outside $34$ to $46\,R_\odot$, the paper's stated uncertainties are wrong. Alternatively, identify an observed X-ray binary with a supergiant donor overfilling its Roche lobe and measure its accretion rate from X-ray luminosity; a rate more than an order of magnitude away from $4\times10^{-3}\,M_\odot\,\mathrm{yr}^{-1}$ would challenge the prediction.
Extended reading notes
Core claim
The central claim is that a pre-common-envelope disk around a neutron star fed through the inner Lagrange point should have $M_{\rm disk}\sim 5\times10^{-3}\,M_\odot$, $R_{\rm disk}\sim 40\,R_\odot$, and $H\sim 5\,R_\odot$ at the moment the in-spiral begins, with an inner-boundary accretion rate of a few $\times10^{-3}\,M_\odot\,\mathrm{yr}^{-1}$. The disk rotates at nearly Keplerian speed near the inner boundary and at 80 to 90 percent of Keplerian at its outer edge, where pressure support matters. Its mid-plane temperature falls as $T\propto r^{-1.1}$, steeper than the $T\propto r^{-3/4}$ law of the standard Shakura-Sunyaev thin-disk model, and the authors attribute the difference to their quasi-isothermal equation of state without explicit cooling. Based on simulations that vary the mass-injection rate, the nozzle velocity, the background density and temperature, and the mesh resolution, they argue the disk mass is reliable to within a factor of a few and the radius to within about 15 percent.
Load-bearing premise
The load-bearing premise is that a 21-year, quasi-isothermal ($\gamma=1.1$) 3D run without explicit cooling or self-gravity, driven by a 1D model of the donor's mass loss, captures the disk's state at the moment the common envelope begins; if the real envelope cools or compresses differently, or the donor responds to mass loss differently, the disk's mass and radius could move outside the stated factor of a few.
Editorial extensions
If this is right
- The neutron star enters the common envelope carrying a disk of about $5\times10^{-3}\,M_\odot$, giving the in-spiral an immediate reservoir of mass and angular momentum that can feed jets or outflows.
- Because the inner accretion rate is roughly a hundred times smaller than the L1 injection rate, most of the transferred mass is stored in the disk or leaves the domain rather than being accreted promptly.
- A jet launched from the inner boundary of this disk could carry a mechanical luminosity near $3\times10^3\,L_\odot$, and a jet launched close to the neutron star surface could reach about $10^8\,L_\odot$, enough to affect envelope unbinding.
- The disk's steeper-than-standard temperature profile implies that radiative cooling must be included before the Shakura-Sunyaev $T\propto r^{-3/4}$ prescription is used for pre-CE disk temperatures.
- The convergence of disk mass, radius, scale height, and accretion rate across refinement levels indicates the predicted properties are numerical, not resolution artifacts.
Reading between the lines
- If the disk is destroyed upon entering the common envelope, its measured mass and angular momentum set the starting budget for any disk that reforms around the in-spiralling neutron star, so these numbers anchor CE-feedback models even if the disk itself does not survive.
- The simulations omit magnetic fields, and the paper notes that Gauss-level fields could be amplified by the magneto-rotational instability within a few orbits; if that happens, magnetic stress may raise the accretion rate above the measured value.
- A comparison run at $\gamma=4/3$ already produces a five-times-smaller and hundred-times-less-massive structure, so if the real envelope contains zones of reduced compressibility, disk formation in this pre-CE phase could be marginal rather than assured.
- Observing a candidate pre-CE system in unstable mass transfer and comparing its inferred accretion rate and disk signatures with these predictions would test whether the simulated 21-year window is representative of the full 30,000-year RLOF phase.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper presents 3D hydrodynamic simulations of Roche-lobe overflow mass transfer from a 7 M_sun red supergiant onto a 1.4 M_sun neutron star, targeting the phase immediately before common-envelope (CE) entry. A 1D MESA simulation supplies a 30,000-year mass-transfer history, while the 3D MEZCAL simulations follow only the last 21 years around the accretor, using a fixed quasi-isothermal equation of state with gamma=1.1 and no explicit cooling. The central claims are that the pre-CE disk has mass ~5e-3 M_sun, radius ~40 R_sun, scale height ~5 R_sun, and accretion rate ~4e-3 M_sun/yr, and that these values are robust to a factor of a few in mass and 15% in radius. The paper includes resolution, injection-rate, nozzle-velocity, background, and adiabatic-index sensitivity tests, as well as a comparison of the measured accretion rate and temperature profile with Shakura-Sunyaev theory.
Significance. If the central numbers hold, this would be a valuable quantitative constraint on accretion feedback in the poorly understood pre-CE phase, with direct consequences for studies of jet feedback and CE outcomes. The paper's strengths are its explicit stress testing: the resolution study (Section 4.4) shows convergence with only 12% mass variation across levels, and the parameter scans in Sections 4.1-4.3 cover several numerical and physical choices. The authors also openly state many limitations, including the absence of cooling and the short simulation window. However, the stated uncertainty budget does not include the dominant thermodynamic sensitivity, and the Shakura-Sunyaev comparison is circular; these issues bound the significance of the claimed numbers unless the claims are narrowed or the physics is extended.
major comments (3)
- [Section 4.5 and Figure 19] The claimed robustness expressed in the abstract and Section 5 ("reasonable within a factor of a few for the mass and 15% for the radius") is not supported for the dominant physical uncertainty. The paper's own 3D run with gamma=4/3 gives Mdisk=5.37e-5 M_sun and Rdisk=15.2 R_sun, versus Mdisk=5.5e-3 M_sun and Rdisk=39 R_sun for sim-0 -- a factor of ~100 in mass and ~2.6 in radius -- and the gamma=5/3 run yields no measurable disk. All variations in Sections 4.1-4.4 keep gamma=1.1 and no explicit cooling, so they cannot bound the sensitivity to the effective thermodynamics. The paper should either add simulations that vary the equation of state/cooling in a physically motivated range, or explicitly restate the central claim as conditional on a near-isothermal, no-cooling model, removing the factor-of-few and 15% statements as global robustness claims.
- [Section 3.1, Eq. (11)] The agreement between the simulated accretion rate and the Shakura-Sunyaev prediction is not an independent validation: Eq. (11) uses the simulation's own Mdisk, cs, and H, assumes Sigma = Mdisk/Rdisk^2, and adopts alpha=0.1 arbitrarily. The predicted rates are therefore partly determined by construction, making the comparison circular. The text should either derive alpha from the measured turbulent stress or shock dissipation in the simulation, or clearly label this as a consistency check rather than a prediction.
- [Section 2.2.2, Table 5, Figure 6] The extrapolation that the 21-year disk mass is "likely only a factor of a few smaller than if the entire phase were modelled" is not directly supported. The cumulative mass of sim-0 is still increasing at t=21 yr (Figure 6, bottom-right panel), and the sim-mdot-2 and sim-mdot-3 runs start at different times and run for different durations without reaching a secular plateau. The paper should quantify the disk growth rate at the end of the simulation and either show evidence of approach to saturation or reframe the CE-entry mass as an upper limit.
minor comments (6)
- [Section 2.2] There is a duplicated word in "We then use use the 3D hydrodynamic numerical code"; please correct.
- [Figure 15 caption] The caption states "Tbg = 105 cm s–1" for what should be a temperature; the units should be K, and the same typo appears in the legend context.
- [References] The Shakura & Sunyaev (1973) reference is listed twice with identical bibliographic data; please consolidate.
- [Section 4.5] The phrase "only slightly higher" for gamma=4/3 compared to gamma=1.1 is imprecise; a change from 1.1 to 1.333 is substantial in compressibility, so the sentence should be rephrased.
- [Section 3.1, Figure 9] The text uses alpha both for the Shakura-Sunyaev viscosity parameter and for the temperature power-law exponent; this is confusing and should be disambiguated with different symbols.
- [Appendix 1.1] The conservation test modifies the boundary conditions and removes the inner inflow boundary, so it does not verify conservation in the production setup; the discussion should acknowledge that this is a simplified check.
Circularity Check
Minor circularity: the Shakura-Sunyaev accretion-rate 'prediction' (Eq. 11) is assembled from the simulation's own disk outputs with an arbitrary α=0.1, so the agreement with the measured rate is a self-referential consistency test, not an independent check; the central disk mass/radius result remains a non-circular forward calculation.
-
fitted input called prediction
[Section 3.1, Eq. (11) and Table 4; restated in Section 5]
"We can therefore compare the numerically-derived accretion rates to those theoretically predicted by Shakura & Sunyaev (1973): Mdot = 3πΣαcsHdisk, ... where we assume Σ = Mdisk/R2 disk). For thin disks, we arbitrarily assume α = 0.1. Using the aforementioned results at the 10.5 and 21 years, we predict accretion rates of 5.0 × 10–4 M⊙ yr–1and 3.7 × 10–3 M⊙ yr–1, respectively, consistent with the accretion rate measured at the same two points in the simulation (Table 4)."
The 'predicted' Shakura-Sunyaev rate is assembled from the same simulation's measured Mdisk, cs, and Hdisk (Eq. 11), closed by an assumed Σ = Mdisk/Rdisk^2 and an arbitrary α = 0.1. The comparison target — 'the accretion rate measured at the same two points in the simulation' (Table 4) — is another output of that same run (Eq. 10). Neither side is independent: the prediction carries no information beyond the run's own disk properties, and the agreement only restates that the run's implied effective α is ≈0.1 under the assumed closure. Because every input to Eq. 11 is an output of the very simulation the check claims to validate, the 'prediction' is a self-referential consistency test, not a confirmation; with α free, the formula could absorb any discrepancy.
full rationale
The central claim (Mdisk ≈ 5×10^−3 M_sun, Rdisk ≈ 40 R_sun, H ≈ 5 R_sun just before CE) is the measured output of a forward 3D Euler-equation integration with a specified mass-injection history from MESA, γ = 1.1, and no explicit cooling (Sec. 2.2.2). No equation defines these outputs in terms of the inputs; they are obtained from cumulative-mass and vertical-density profiles (Sec. 3.1). That core derivation is not circular. The one self-referential step is the Shakura-Sunyaev 'prediction' (Sec. 3.1, Eq. 11): predicted Mdot = 3πα(Mdisk/Rdisk^2)csH is built from the same run's measured Mdisk, cs, H with an arbitrary α = 0.1 and compared to the same run's measured accretion rate (Eq. 10, Table 4). The agreement is a consistency test with a free efficiency parameter — it states that the run's implied effective α ≈ 0.1 — not an independent validation; but it is non-load-bearing for the headline disk parameters. The γ = 4/3 run (Sec. 4.5) lowering Mdisk by ≈100× and γ = 5/3 erasing the measurable disk is a real limitation of the quoted 'factor of a few' mass accuracy, and the paper itself concedes 'more reasonable cooling physics would need to be included'; this is a physical-robustness concern (correctness risk), not circularity, and it is disclosed rather than hidden. Self-citations (López-Cámara et al. 2019/2020/2022; Moreno Méndez et al. 2017/2022; De Colle et al. 2012) are contextual and non-load-bearing; the γ = 1.1 choice rests on external prior work (Makita et al. 2000; MacLeod & Ramirez-Ruiz 2015; Murguia-Berthier et al. 2017) and is explicitly stress-tested in Sec. 4.5. No uniqueness theorem is imported. Score 3: minor, non-load-bearing circularity in the SS cross-check; the central simulation stands on its own.
Assumptions & free parameters
free parameters (4)
- Adiabatic index gamma =
1.1
- Shakura-Sunyaev alpha =
0.1
- Nozzle injection velocity vL1 =
7.7e4 cm/s (sim-0)
- Background density and temperature =
rho_bg = 2.6e-22 g/cm3, T_bg = 1e5 K
assumptions (5)
- domain assumption Ideal gas quasi-isothermal equation of state, P = (gamma - 1) rho e, with gamma = 1.1.
- domain assumption No self-gravity of the disk; only point-mass potentials of the donor and accretor in a rotating frame.
- domain assumption The MESA 1D mass-transfer rate and binary parameters are accurate.
- domain assumption The Lubow-Shu and Jackson nozzle prescription describes the mass stream through L1.
- domain assumption Inviscid Euler equations with numerical viscosity and turbulent shocks providing angular momentum transport.
Cite this review
Pith. "Pith review of Three-dimensional simulations of accretion disks in pre-CE systems." pith.science (2026). https://pith.science/paper/PP6CS7VV
@misc{pith2026250202933,
author = {Pith},
title = {Pith review of: Three-dimensional simulations of accretion disks in pre-CE systems},
year = {2026},
howpublished = {\url{https://pith.science/paper/PP6CS7VV}},
note = {Machine review of arXiv:2502.02933}
}
abstract
Before a binary system enters into a common envelope (CE) phase, accretion from the primary star onto the companion star through Roche Lobe overflow (RLOF) will lead to the formation of an accretion disk, which may generate jets. Accretion before and during the CE may alter the outcome of the interaction. Previous studies have considered different aspects of this physical mechanism. Here we study the properties of an accretion disk formed via 3D hydrodynamic simulations of the RLOF mass transfer between a 7 M$_\odot$, red supergiant star and a 1.4 M$_\odot$, neutron star companion. We simulate only the volume around the companion for improved resolution. We use a 1D implicit MESA simulation of the evolution of the system during 30,000 years between the on-set of the RLOF and the CE to guide the binary parameters and the mass-transfer rate, while we simulate only 21 years of the last part of the RLOF in 3D using an ideal gas isothermal equation of state. We expect that a pre-CE disk under these parameters will have a mass of $\sim 5\times 10^{-3}$ M$_\odot$ and a radius of $\sim$40 R$_\odot$ with a scale height of $\sim$5 R$_\odot$. The temperature profile of the disk is shallower than that predicted by the formalism of Shakura and Sunyaev, but more reasonable cooling physics would need to be included. We stress test these results with respect to a number of physical and numerical parameters, as well as simulation choices, and we expect them to be reasonable within a factor of a few for the mass and 15% for the radius. We also contextualize our results within those presented in the literature, in particular with respect to the dimensionality of simulations and the adiabatic index. We discuss the measured accretion rate in the context of the Shakura and Sunyaev formalism and debate the viscous mechanisms at play, finishing with a list of prospects for future work.
Figures
Figures from the paper (16 more)
Forward citations
Cited by 2 Pith papers
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Mass-feeding of jet-launching white dwarfs in grazing and common envelope evolution
White dwarfs entering a giant's envelope may grow a one-solar-radius accretion disk that launches jets powered by gravitational energy, explaining jet-shaped planetary nebulae and luminous red novae.
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Jet-shaped filamentary ejecta in common envelope evolution
New 3D simulations show Rayleigh-Taylor instabilities turn jet-driven common-envelope ejecta into filaments, with faster envelope rotation making spiral arms more prominent.
Reference graph
Works this paper leans on
-
[1]
P., Abbott, R., Abbott, T., et al
Abbott, B. P., Abbott, R., Abbott, T., et al. 2016, Physical review letters, 116, 241103
work page 2016
- [2]
-
[3]
A., & Hawley, J
Balbus, S. A., & Hawley, J. F. 1991, ApJ, 376, 214
1991
-
[4]
E., Lee, C.-H., & Moreno Méndez, E
Brown, G. E., Lee, C.-H., & Moreno Méndez, E. 2007, ApJ, 671, L41
work page 2007
-
[5]
2023, Monthly Notices of the Royal Astronomical Society, 524, 471
Cehula, J., & Pejcha, O. 2023, Monthly Notices of the Royal Astronomical Society, 524, 471
work page 2023
- [6]
-
[7]
Chevalier, R. A. 2012, The Astrophysical Journal Letters, 752, L2 De Colle, F., Granot, J., López-Cámara, D., & Ramirez-Ruiz, E. 2012, The Astrophysical Journal, 746, 122
work page 2012
- [8]
Show all 41 references
-
[9]
Eggleton, P. P. 1983, ApJ, 268, 368
1983
-
[10]
1998, The Astrophysical Journal, 502, L9
Fryer, C., & W oosley, S. 1998, The Astrophysical Journal, 502, L9
1998
-
[11]
2021, Phys
Hayashi, K., Kawaguchi, K., Kiuchi, K., Kyutoku, K., & Shibata, M. 2021, Phys. Rev. D, 103, 043007
2021
-
[12]
2022, MNRAS, 514, 3212
Hillel, S., Schreier, R., & Soker, N. 2022, MNRAS, 514, 3212
2022
-
[13]
Iben, I., J., & Tutukov, A. V. 1984, ApJS, 54, 335
1984
-
[14]
2013, The Astronomy and Astro- physics Review, 21, 1
Ivanova, N., Justham, S., Chen, X., et al. 2013, The Astronomy and Astro- physics Review, 21, 1
2013
-
[15]
2017, The Astrophysical Journal, 835, 145
Jackson, B., Arras, P., Penev, K., Peacock, S., & Marchant, P. 2017, The Astrophysical Journal, 835, 145
2017
-
[16]
Lau, M. Y. M., Hirai, R., González-Bolívar, M., et al. 2022, MNRAS, 512, 5462 López-Cámara, D., De Colle, F., & Moreno Méndez, E. 2019, MNRAS, 482, 3646 López-Cámara, D., De Colle, F., Moreno Méndez, E., Shiber, S., & Iaconi, R. 2022, MNRAS, 513, 3634 López-Cámara, D., Moreno ...
2022
-
[17]
H., & Shu, F
Lubow, S. H., & Shu, F. H. 1975, The Astrophysical Journal, 198, 383
1975
-
[18]
2017, The Astrophysical Journal, 838, 56
MacLeod, M., Antoni, A., Murguia-Berthier, A., Macias, P., & Ramirez-Ruiz, E. 2017, The Astrophysical Journal, 838, 56
2017
-
[19]
2015, The Astrophysical Journal, 803, 41
MacLeod, M., & Ramirez-Ruiz, E. 2015, The Astrophysical Journal, 803, 41
2015
-
[20]
2000, Monthly Notices of the Royal Astronomical Society, 316, 906
Makita, M., Miyawaki, K., & Matsuda, T. 2000, Monthly Notices of the Royal Astronomical Society, 316, 906
2000
-
[21]
1994, in Theory of Accretion Disks — 2, ed
Mineshige, S., Honma, F., Hirano, A., et al. 1994, in Theory of Accretion Disks — 2, ed. W. J. Duschl, J. Frank, F. Meyer, E. Meyer-Hofmeister, & W. M. Tscharnuter (Dordrecht: Springer Netherlands), 187–193
1994
-
[22]
2017, ApJS, 230, 15 Moreno Méndez, E
Moe, M., & Di Stefano, R. 2017, ApJS, 230, 15 Moreno Méndez, E. 2022, arXiv e-prints, arXiv:2207.14765 Moreno Méndez, E., López-Cámara, D., & De Colle, F. 2017, MNRAS, 470, 2929
2017 arXiv
-
[23]
2017, The Astrophysical Journal, 845, 173
Murguia-Berthier, A., MacLeod, M., Ramirez-Ruiz, E., Antoni, A., & Macias, P. 2017, The Astrophysical Journal, 845, 173
2017
-
[24]
2011, ApJS, 192, 3
Paxton, B., Bildsten, L., Dotter, A., et al. 2011, ApJS, 192, 3
2011
-
[25]
2013, ApJS, 208, 4
Paxton, B., Cantiello, M., Arras, P., et al. 2013, ApJS, 208, 4
2013
-
[26]
2015, ApJS, 220, 15
Paxton, B., Marchant, P., Schwab, J., et al. 2015, ApJS, 220, 15
2015
-
[27]
B., et al
Paxton, B., Schwab, J., Bauer, E. B., et al. 2018, ApJS, 234, 34
2018
-
[28]
2019, ApJS, 243, 10
Paxton, B., Smolec, R., Schwab, J., et al. 2019, ApJS, 243, 10
2019
-
[29]
Pjanka, P., & Stone, J. M. 2020, ApJ, 904, 90
2020
-
[30]
E., & King, A
Pringle, J. E., & King, A. 2014, Astrophysical Flows (Cambridge University Press)
2014
-
[31]
M., Hamann, W
Ramachandran, V., Oskinova, L. M., Hamann, W. R., et al. 2022, A&A, 667, A77
2022
-
[32]
2009, Nature, 460, 1091
Ramirez-Ruiz, E., & Lee, W. 2009, Nature, 460, 1091
2009
-
[33]
2025, arXiv e-prints, arXiv:2503.04442
Rea, N., & De Grandis, D. 2025, arXiv e-prints, arXiv:2503.04442
2025 arXiv
-
[34]
1977, Astronomy and Astrophysics, 62, 317
Savonije, G. 1977, Astronomy and Astrophysics, 62, 317
1977
-
[35]
I., & Sunyaev, R
Shakura, N. I., & Sunyaev, R. A. 1973, A&A, 24, 337
1973
-
[36]
I., & Sunyaev, R
Shakura, N. I., & Sunyaev, R. A. 1973, Astronomy and Astrophysics, 24, 337
1973
-
[37]
2024, MNRAS, 532, 692
Shiber, S., & Iaconi, R. 2024, MNRAS, 532, 692
2024
-
[38]
2019, MNRAS, 488, 5615
Shiber, S., Iaconi, R., De Marco, O., & Soker, N. 2019, MNRAS, 488, 5615
2019
-
[39]
M., Kramer, M., Freire, P
Tauris, T. M., Kramer, M., Freire, P. C. C., et al. 2017, ApJ, 846, 170
2017
-
[40]
2007, Ap&SS, 311, 35
Wardle, M. 2007, Ap&SS, 311, 35
2007
-
[41]
1995, Cataclysmic Variable Stars, Cambridge Astrophysics (Cam- bridge University Press), doi:10.1017/CBO9780511586491 18 Ana L
Warner, B. 1995, Cataclysmic Variable Stars, Cambridge Astrophysics (Cam- bridge University Press), doi:10.1017/CBO9780511586491 18 Ana L. Juarez-Garcia et al. Appendix 1. Numerical considerations Appendix 1.1 Conservation of mass, energy and angular momentum As we explain in ...
1995 doi
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