REVIEW 3 major objections 4 minor 31 references
The failed failed-supernova scenario of M31-2014-DS1
T0 review · 3 major / 4 minor · reviewed 2026-08-03 · deepseek-v4-flash
Pith's one-line read The failed-supernova explanation for M31-2014-DS1 would make the star fade too slowly and shine too bright, so the paper says the fading is more likely a dusty binary interaction.
desk verdict Worth reading and worth refereeing, but the fine-tuning argument has a factor-of-η slip: Eq. (4) treats the full fallback mass as jet-launching mass, ignoring the ≳99% centrifugal-barrier loss the paper itself accepts. 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 central object is the parameter j_conv = v_conv r, the specific angular momentum of the convective cells in the envelope, taken from a stripped yellow-supergiant model and used to set the initial radius R_d,0 of a fallback disk around the black hole (equation 1). Around this disk the argument builds a short quantitative chain: the disk radius sets the escape and terminal velocity of a disk wind (equation 6), the assumed jet mass fraction f_j and jet velocity set whether jets unbind the remaining bound gas (equations 3–4), and the radiative cooling time of the outflow interaction zone (equation 5) converts the outflow power into a predicted luminosity (equation 7). The equations scale ste
What would settle it
Detect the predicted X-ray emission from M31-2014-DS1: the paper estimates that outflow interaction should radiate at least an order of magnitude above the observed luminosity (L_X ≳ 10^36 erg/s), so a detection near that level in the next few years would falsify the paper's conclusion, while continued upper limits would support it.
Extended reading notes
Core claim
On its own terms, the paper establishes that the decade-long fading of M31-2014-DS1 is hard to reproduce in the proposed failed-supernova picture. Taking the standard estimate that the pre-collapse envelope's convection gives infalling gas a specific angular momentum of about 7×10^18 cm^2 s^-1, the first fallback material forms an accretion disk near one solar radius around a five-solar-mass black hole. If that disk launches jets carrying even a tenth of a percent of the accreted mass, the jets' energy exceeds the binding energy of the remaining bound envelope, so the backflow should be cut off within the first year rather than feeding the black hole for years. Even in the inefficient case w
Load-bearing premise
The whole critique leans on assumptions about how much spin the star's churning outer layers give the infalling gas and how efficiently the resulting disk turns that gas into jets; if either value is far smaller than assumed, the predicted excess brightness and the fine-tuning problem disappear.
Editorial extensions
If this is right
- M31-2014-DS1 should no longer be cited as observational support for the failed-supernova scenario or for black-hole formation through low-energy explosions with long-term fallback.
- The observed upper limits on X-ray and sub-millimeter emission are consistent with a picture in which fallback accretion shuts off early, rather than powering a decade-long fade.
- The type II intermediate-luminosity optical transient scenario—where a violent binary interaction ejects dusty gas that obscures the central source—becomes the more likely explanation for the event.
- Within the neutrino-driven explosion framework, the event cannot be used as evidence that a non-negligible fraction of massive stars collapse quietly into black holes.
Reading between the lines
- The same over-luminosity test could be applied to other failed-supernova candidates: any candidate showing a decade-long fade without bright X-ray or radio emission would face the same tension between fallback models and observations.
- The argument turns a single-event debate into a general diagnostic: the ratio of expected fallback luminosity to observed luminosity may help separate genuine black-hole-forming collapses from dust-veiled binary eruptions.
- Because the conclusion depends steeply on the assumed convective angular momentum and jet-launching efficiency, a grid of stripped-star models with varied masses and metallicities would sharpen or soften the fine-tuning claim.
- If the binary-interaction scenario is right, the source may reappear or show an eccentric-orbit signature in future observations—a concrete test that the paper's author previously predicted for this object.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This paper critiques the failed-supernova interpretation of the fading yellow supergiant M31-2014-DS1 proposed by De et al. (2024, 2026). It argues that the convective pre-collapse envelope supplies stochastic angular momentum, causing fallback material to form an accretion disk at ~1 R_sun around the newly formed black hole. The paper claims that (i) the resulting jittering jets or disk winds would unbind most of the bound mass and shut down backflow within the first year, so De et al.'s requirement of continued inefficient accretion for >10 years is fine-tuned; and (ii) even if most bound mass is ejected by the centrifugal barrier, the implied outflow power of ~3.7e5 L_sun, radiated after rapid cooling in the interaction region, is an order of magnitude or more above the observed luminosity. The author concludes that M31-2014-DS1 is more likely a type II ILOT (binary interaction with dust ejection) and does not support the failed-supernova scenario of the neutrino-driven mechanism.
Significance. If the arguments hold, the paper would remove a recently claimed observational support for the neutrino-driven failed-supernova mechanism and strengthen the alternative type II ILOT interpretation. It is a timely contribution to an active debate, and its strength lies in translating the scenario into simple order-of-magnitude estimates that can be checked with multi-wavelength observations. The paper is transparent about its limitations ('I cannot completely rule out the failed-supernova scenario') and does not overclaim its certainty. However, the central estimates depend on parameters imported from the author's own jittering-jets framework and a single stellar model co-authored by the author. The paper does not provide simulations or new observations, and its conclusions are only as robust as these parameter choices. The over-luminosity argument, in particular, is a falsifiable prediction that could be decisive, but it requires a sensitivity analysis to be fully convincing.
major comments (3)
- [§2, Eqs. (3)–(4)] The derivation sets the mass that launches jets equal to the entire still-bound mass M_b accreted between 0.5 and 1 yr. But the manuscript itself states (Sec. 2, just after Eq. 1) that De et al. (2026) find that ≳99% of the initially bound material is expelled by the random angular momentum barrier, and calls this 'unavoidable.' Therefore the mass that actually reaches the inner disk and can power jets is M_acc = η M_b with η ≲ 0.01, not M_b. Inserting η into Eq. (4) gives v_b ≈ η f_j v_jet. For η=0.01 and f_j=10^-3, v_b≈1 km/s, far below the ≈50 km/s escape speed; even f_j=0.01 gives only ≈10 km/s. The claim that 'for typical f_j=0.01–0.1 the initial accretion will completely shut down backflow' thus implicitly assumes η=1, which is inconsistent with the paper's own premise. The fine-tuning argument should be restated with η explicit, and the region in (η, f_j) that actually unbinds the
- [§3, Eq. (7) and Fig. 1] The over-luminosity constraint relies on j_conv ≈ 7×10^18 cm^2 s^-1 from one stellar model (Cohen et al. 2025) with M_* = 9.5 M_sun, whereas the De et al. (2026) failed-supernova model has a progenitor of M ≈ 6.7 M_sun at explosion. The wind power scales as v_d,wind^2 ∝ j_conv^-2. A factor 2 increase in j_conv (to 1.4×10^19) lowers \bar E_d,wind from 3.7×10^5 L_sun to ≈9×10^4 L_sun, and a factor 3 lowers it to ≈4×10^4 L_sun, no longer 'an order of magnitude or more' above the observed ≈10^4 L_sun. Since convective velocities in stripped stars can plausibly vary by factors of a few, the author should either compute j_conv for the actual De et al. progenitor or demonstrate that the result is insensitive to the mass and stripping history. Without this, the luminosity argument is not robust.
- [§3, Eq. (7)] The calculation implicitly assumes that essentially all of the kinetic power of the centrifugal-barrier wind is radiated after interaction with the bound/ejected gas. However, the wind from a rotating accretion disk is likely anisotropic, and Beasor et al. (2026) find the obscuring dust distribution is non-spherical. The paper does not estimate the covering factor or the fraction of the wind that actually shocks against dense bound gas. If a substantial fraction of the outflow escapes through low-density polar regions, the radiated luminosity could be well below the value in Eq. (7). A quantitative geometric estimate (or an argument that jittering changes the wind direction on a timescale short compared to the 10-yr evolution) is needed before the luminosity constraint can be considered decisive.
minor comments (4)
- [Fig. 1 caption] The axes lack units; please specify radius in R_sun, velocity in km/s, and mass in M_sun. Also, 'striped' should be 'stripped.'
- [§2, paragraph before Eq. (2)] The statement that the mass accreted between 0.5 and 1 yr equals the mass still bound after 1 yr follows from a ∝t^-2 fallback rate, but this should be stated explicitly to make the derivation transparent.
- [§3, Eq. (5)] The cooling function Λ depends on metallicity and ionization state; please state the assumed abundance (e.g., solar) and the temperature range. Also define n_H explicitly and whether it is the pre-shock or post-shock density.
- [§2, Eq. (3)] The inequality sign in Eq. (3) is not explained; if v_jet=10^5 km/s and f_j=10^-3, the ratio is 4000, not larger. Please clarify whether '>' accounts for possible relativistic jets.
Circularity Check
No significant circularity: the critique tests the failed-supernova model against its own parameters and external observations; self-citations are prominent but not used to define the target result.
full rationale
The paper's central claims are (i) fallback accretion with stochastic angular momentum would launch jets/winds that shut down backflow, and (ii) the resulting outflow would radiate roughly an order of magnitude above the observed luminosity. Both are forward-model arguments: the bound mass, shell density, black-hole mass, and fallback rate are taken from De et al. (2024, 2026), and the observed luminosities are taken from Beasor et al. (2026) and De et al. (2026). The only self-cited inputs are the convective angular-momentum scale j_conv from Cohen, Bear & Soker (2025) and the 'typical' jet efficiency f_j from the author's jittering-jets framework. These are assumptions imported into the test, not quantities fitted to M31-2014-DS1; the predicted luminosity scales with them but is not identical to them by construction. A possible inconsistency noted by a reader—that Eqs. (3)-(4) use the full fallback mass as accreted mass while the same scenario invokes a >99% centrifugal-barrier loss—is a quantitative consistency concern about the argument, not a case of the paper deriving its conclusion from its own premises in a definitionally forced way. The self-citations to Soker (2024) and related JJEM papers support the alternative ILOT scenario, but the paper does not claim to prove that scenario from M31-2014-DS1; its main finding is that the failed-supernova scenario is not forced by the data. No circular reduction is exhibited.
Assumptions & free parameters
free parameters (4)
- jet mass-loading fraction f_j =
assumed 1e-3–1e-1
- post-shock temperature T =
1e8 K
- bound mass M_b =
0.05 M_sun
- convective specific angular momentum j_conv =
7e18 cm^2 s^-1
assumptions (5)
- domain assumption The stripped post-red-supergiant model of Cohen et al. (2025) represents the M31-2014-DS1 progenitor and gives j_conv ≈ 7e18 cm^2 s^-1.
- domain assumption Fallback gas with stochastic angular momentum forms intermittent accretion disks that launch jets carrying f_j of the accreted mass at ~1e5 km/s.
- domain assumption The outflow terminal velocity equals the Keplerian velocity at the initial disk radius (Eq. 6).
- domain assumption The radiative cooling time at constant pressure with Lambda ≥ 3e-23 erg cm^3 s^-1 applies, so most interaction energy is radiated.
- domain assumption The De et al. (2026) scenario parameters—ejected mass 0.1 M_sun, bound mass 0.05 M_sun, shell 40–80 AU, n_H ≈ 1e10 cm^-3, M_BH = 5 M_sun, fallback rate ∝ t^-2—are correct.
Cite this review
Pith. "Pith review of The failed failed-supernova scenario of M31-2014-DS1." pith.science (2026). https://pith.science/paper/O4A42QDC
@misc{pith2026260114497,
author = {Pith},
title = {Pith review of: The failed failed-supernova scenario of M31-2014-DS1},
year = {2026},
howpublished = {\url{https://pith.science/paper/O4A42QDC}},
note = {Machine review of arXiv:2601.14497}
}
read the original abstract
I examine a recently proposed failed-supernova scenario for the fading of the yellow supergiant event M31-2014-DS1, and find that it requires unlikely fine-tuned parameters to work, if at all. In the failed-supernova scenario, most of the yellow supergiant collapsed to form a black hole. Due to the energy carried by neutrinos from the cooling, collapsing core, gravity decreases, leading to the ejection of a small fraction of the outer envelope, some of which remains bound. The fallback accreted gas possesses large angular-momentum fluctuations due to the pre-collapse envelope convection. The fallback material forms intermittent accretion disks around the black hole that launch jets (or disk wind), which unbind most of the bound material. The failed-supernova scenario for M31-2014-DS1 requires that only <1% of the bound material be accreted by the black hole, but the jets do not shut down the backflow for over 10 years. I find this fine-tuned requirement unlikely. I also find that, due to the rapid radiative cooling of the outflow interaction zone with the outer gas, the expected radiation is about an order of magnitude or more above the observed value. These, as well as earlier challenges raised against the failed-supernova scenario, make the alternative type II intermediate-luminosity optical transient scenario, in which fading is due to dust ejection in a violent binary interaction, more likely. The fading event M31-2014-DS1 does not support the failed-supernova scenario predicted by the neutrino-driven explosion mechanism of core-collapse supernovae.
Figures
Reference graph
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Reviewed August 3, 2026 · model on record in the stance chip above.
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