Exploring the effect of mixing in Low-Luminosity Type IIp Supernovae by modeling SN 2024abfl

Abigail Polin; Akshith Karri; Paul Duffell

REVIEW 2 major objections 5 minor 13 references

Exploring the effect of mixing in Low-Luminosity Type IIp Supernovae by modeling SN 2024abfl

T0 review · 2 major / 5 minor · reviewed 2026-07-10 · grok-4.5

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Pith's one-line read Turning off ejecta mixing in models of SN 2024abfl reproduces its flat plateau and steep drop to the nickel tail.

desk verdict Clean MESA+STELLA proof-of-concept that zero artificial mixing reproduces SN 2024abfl's steep drop with the published parameters; the leap from that extreme to 'limited mixing' is the soft spot. read the letter →

arxiv 2607.08424 v1 pith:SVK2IYSL submitted 2026-07-09 astro-ph.HE astro-ph.SR

Akshith Karri , Abigail Polin , Paul Duffell This is my paper · ORCID

classification astro-ph.HEastro-ph.SR

keywords low-luminosityTypeIIpsupernovaeSN2024abflejectamixingRayleigh-TaylorinstabilityMESASTELLAcore-collapseplateaulightcurves

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

SN 2024abfl is a low-luminosity Type IIp supernova whose light curve stays unusually flat for about 126 days and then falls by roughly 2.4 magnitudes in only a few days onto a faint radioactive tail. That sharp edge is harder to produce than the smoother transitions seen in other low-luminosity Type II events. Using a one-dimensional MESA–STELLA pipeline, the authors show that simply disabling artificial boxcar and Rayleigh–Taylor mixing during shock breakout yields a light curve with the observed flat plateau and abrupt drop, while still employing the previously suggested progenitor mass, radius, and explosion energy. The result is offered as a proof-of-concept that limited mixing, rather than exotic progenitor parameters alone, can shape the distinctive morphology of some low-luminosity Type IIp supernovae and may help explain how they differ from ordinary Type IIp events.

What carries the argument

The MESA–STELLA pipeline with mixing toggles: by turning off both artificial boxcar smoothing and Rayleigh–Taylor instability mixing during shock breakout, the one-dimensional calculation isolates the effect of suppressed ejecta mixing on the plateau-to-tail transition.

What would settle it

A multi-dimensional radiation-hydrodynamics calculation of the same progenitor and explosion energy that includes realistic Rayleigh–Taylor and convective mixing but still fails to produce a steep plateau-to-tail drop would rule out the limited-mixing explanation.

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Extended reading notes

Core claim

Disabling boxcar smoothing and Rayleigh–Taylor instability mixing during the shock-breakout phase of a MESA–STELLA calculation produces a bolometric light curve whose flat plateau and steep post-plateau decline match the distinctive morphology of SN 2024abfl, using a 10-solar-mass solar-metallicity progenitor, pre-collapse radius ~355 solar radii, explosion energy 1.4 imes10^50 erg, and 0.01 solar masses of nickel-56.

Load-bearing premise

That completely switching off the artificial mixing switches in a one-dimensional code is a fair stand-in for the limited mixing that might actually occur in three-dimensional ejecta.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

The one thing worth knowing is that they take the published 10 M☉ / ~355 R☉ / 1.4e50 erg / 0.01 M☉ Ni setup for SN 2024abfl and show that simply turning off boxcar and RTI mixing in their MESA+STELLA pipeline produces a flat plateau and a sharp drop that looks like the observed ~2.4 mag in ~5.5 days, while the mixed run does not. That is a transparent numerical experiment and a useful application of a known effect (Utrobin et al. 2017 already said efficient mixing smooths the transition) to a new, extreme light curve.

What they do well: the pipeline is described clearly, the energy and radius trends in Fig. 1b,c match the expected Kasen/Woosley and Hamuy scalings, and they are honest that distance is poorly constrained and that early CSM is ignored. The mixing-on vs mixing-off comparison in Fig. 1a is the actual result; everything else is supporting context. Citations look appropriate and not padded.

Soft spots, in proportion. The stress-test is right: they only ever compute the two extremes and then talk about 'limited mixing' in the Discussion. Zero artificial mixing in 1-D is not a physical proxy for modest 3-D redistribution; without an intermediate grid (partial RTI efficiency, reduced boxcar, modest Ni mixing) the claim that suppressed-but-not-zero mixing is sufficient remains unshown. There are also no χ^{2} or residual metrics, no public code/data, and the distance degeneracy is acknowledged but not quantified. Those are real limitations for a short proof-of-concept, not fatal ones.

This is for people who model Type II light curves or who are following the new LLSN sample. It is not a theory paper and does not reorganize anything, but it is a clean enough demonstration that a referee should see it. I would accept it for peer review, expect the intermediate-mixing and quantitative-fit requests, and cite the figure if I am writing about plateau-to-tail morphology.

Referee Report

2 major / 5 minor

Summary. The manuscript models the bolometric light curve of the low-luminosity Type IIP supernova SN 2024abfl with a MESA+STELLA pipeline. Using a 10 M☉ solar-metallicity progenitor, pre-collapse radius ≈355 R☉, explosion energy 1.4 imes10^50 erg and 0.01 M☉ of 56Ni (parameters taken from Gerard et al. 2026), the authors show that completely disabling artificial boxcar smoothing and Rayleigh–Taylor instability (RTI) mixing during shock breakout produces a flat plateau and a steep drop into the radioactive tail that qualitatively matches the observed morphology, whereas models with mixing yield a more gradual transition. Parameter variations of explosion energy and progenitor radius (with mixing off) recover the expected trends of plateau luminosity and duration. The work is presented as a proof-of-concept that limited ejecta mixing may distinguish this event from typical Type IIP supernovae.

Significance. If the morphological effect of reduced mixing survives more realistic intermediate-mixing calculations and multi-dimensional checks, the paper would supply a concrete, observationally motivated diagnostic for ejecta mixing in low-luminosity Type IIP events and would help explain why SN 2024abfl’s plateau-to-tail transition is steeper than those of SN 2003Z or SN 2005cs. The use of a publicly documented MESA/STELLA pipeline and the explicit comparison of mixed versus unmixed light curves are strengths that make the result falsifiable and reproducible. The contribution remains modest because the demonstration is confined to the extreme zero-mixing numerical limit and because distance uncertainties and early CSM interaction are left unquantified.

major comments (2)

Section 3.1 and Figure 1(a) compare only the two extremes: full RTI+boxcar mixing versus both mechanisms completely disabled. The Discussion then equates the zero-mixing case with “limited mixing.” The central claim is that suppressed (not necessarily zero) mixing can reproduce the steep drop while retaining the proposed progenitor parameters. Without an intermediate grid (partial RTI efficiency, reduced boxcar width, or modest 56Ni redistribution), it remains unshown whether any physically plausible intermediate mixing level still yields a comparably steep transition. An intermediate-mixing suite is required to convert the numerical limit into a proof-of-concept for limited mixing.
The abstract and Section 3 state that the unmixed model “mimics” and “reproduces the overall morphology” of SN 2024abfl, yet no quantitative goodness-of-fit metric, residual, or uncertainty band is reported for the bolometric light curve. Given the acknowledged distance degeneracies (Introduction) and the free parameters held fixed from Gerard et al. (2026), a quantitative comparison (e.g., χ^{2} or magnitude residuals over the plateau and drop) is needed to substantiate that the zero-mixing model is preferred over the mixed model at a statistically meaningful level.

minor comments (5)

Abstract: the inequality for peak magnitudes is written “> -15.5” while the body text uses “≥ -15.5”; the two statements should be made consistent.
Keywords: “Core-colllapse” contains a triple-l typo.
Figure 1 caption and panels (b,c) should state explicitly that the energy and radius sequences are computed with mixing disabled, so that readers do not misattribute the morphology solely to those parameters.
Section 2: the custom pipeline is referenced as “A. Karri et al. 2026” (an AAS abstract); a brief description of the modifications to the ccsn_II and STELLA interfaces would improve reproducibility.
Discussion: early CSM interaction is noted as omitted; a short statement of how its inclusion would (or would not) affect the plateau-to-tail morphology would strengthen the interpretation.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: toggling artificial mixing is an independent numerical experiment against external light-curve data and externally proposed parameters.

full rationale

The paper’s central claim is that disabling boxcar and RTI mixing in the MESA/STELLA pipeline produces a flat plateau and steep drop that better matches the observed bolometric light curve of SN 2024abfl while retaining the progenitor mass, radius, explosion energy and nickel mass previously proposed by Gerard et al. (2026). Those parameters are taken as fixed external inputs; the morphological change is a direct numerical output of the hydro/radiative-transfer calculation, not a quantity that is fitted and then re-labeled as a prediction, nor a quantity defined in terms of the mixing switch itself. The comparison is made to an independent observational data set. Self-citations (the authors’ own pipeline description) are methodological only and do not underwrite the scientific result. No uniqueness theorem, ansatz smuggled via self-citation, or renaming of a known empirical pattern appears. The derivation chain is therefore self-contained against external benchmarks and exhibits none of the six enumerated circularity patterns.

Assumptions & free parameters 5 free parameters · 3 assumptions · 0 invented entities

The central claim rests on standard stellar-evolution and radiation-hydrodynamics tools plus a small set of free parameters taken from the observational literature and two numerical switches (RTI and boxcar mixing). No new physical entities are introduced; the main modeling assumptions are the validity of 1-D MESA/STELLA and the physical meaningfulness of completely disabling artificial mixing.

free parameters (5)

progenitor zero-age main-sequence mass = 10 M⊙
Fixed at 10 M⊙ following Gerard et al. 2026; not re-derived from the light curve in this work.
explosion energy = 1.4e50 erg
Set to 1.4×10^50 erg to match the observed luminosity scale; varied in a sensitivity suite but the fiducial value is chosen to fit.
synthesized 56Ni mass = 0.01 M⊙
Fixed at 0.01 M⊙ to set the radioactive-tail luminosity.
pre-collapse stellar radius = 1.65 AU
Set to 1.65 AU (~355 R⊙); varied in a sensitivity suite but the fiducial value is chosen for the final model.
RTI and boxcar mixing switches = off (for the preferred model)
Binary on/off toggles that constitute the main experimental variable; the “off” state is the load-bearing choice for the steep-drop claim.

assumptions (3)

domain assumption One-dimensional MESA stellar evolution plus STELLA radiation-hydrodynamics adequately capture the plateau and transition morphology of Type IIP light curves.
Invoked throughout Methods and Results; the entire model grid is generated inside this pipeline.
ad hoc to paper Completely disabling artificial boxcar smoothing and Rayleigh–Taylor instability mixing is a physically informative proxy for “limited mixing” in real ejecta.
Stated in Section 3.1 and Discussion; the paper itself notes that real ejecta are unlikely to be completely unmixed.
domain assumption Nearby circumstellar interaction can be neglected for the plateau and transition phases modeled here.
Explicitly stated in Discussion; early-time CSM is omitted by construction.

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Cite this review

Pith. "Pith review of Exploring the effect of mixing in Low-Luminosity Type IIp Supernovae by modeling SN 2024abfl." pith.science (2026). https://pith.science/paper/SVK2IYSL

@misc{pith2026260708424,
  author       = {Pith},
  title        = {Pith review of: Exploring the effect of mixing in Low-Luminosity Type IIp Supernovae by modeling SN 2024abfl},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/SVK2IYSL}},
  note         = {Machine review of arXiv:2607.08424}
}

read the original abstract

Low-luminosity Type IIp supernovae (LLSNe) are SN IIps with peak magnitudes > -15.5 and plateau magnitudes between -13.5 and -15.5 in the V band. SN 2024abfl is an LLSN with a unique light curve, particularly the steep drop in luminosity observed after the plateau phase makes it an interesting candidate for modeling core-collapse supernova mechanisms. Using a custom pipeline involving MESA and STELLA, we investigate the possibility of suppressed ejecta mixing as a cause of the steep drop-off from the plateau phase. We find that turning off mixing mechanisms during shock breakout can mimic the distinct flat plateau and steep luminosity drop into the radioactive tail of the light curve while using previously proposed progenitor mass, radius and explosion energy parameters. Using these results as a proof-of-concept, exploring the effects of limited mixing in LLSNe candidates could give us better insight into how they differ from Typical Type IIp SNe.

Figures

Figures reproduced from arXiv: 2607.08424 by the authors.

**Figure 1.** (a) Bolometric light-curve fit to SN 2024abfl (white points), showing models computed with (dashed line) and without (solid line) RTI-induced mixing. (b) Effects of varying explosion energy while holding other model parameters fixed, demonstrating how luminosity drops while extending the plateau phase duration as explosion energy decreases. (c) Effects of varying progenitor radius showing how a decrease in radius sh… view at source ↗

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Works this paper leans on

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Reviewed July 10, 2026 · model on record in the stance chip above.

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work page doi:10.1134/1.1958107 2005

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work page doi:10.1051/0004-6361:20054594 2006

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E., Clayton, G

Gerard, M., Andrews, J. E., Clayton, G. C., et al. 2026, SN 2024abfl: A Flat-Plateau, Low-Luminosity Type IIP Supernova with Early CSM Interaction, https://arxiv.org/abs/2601.02638

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2024, Light Curve Fitting v0.10.0, v0.10.0 Zenodo, doi: 10.5281/zenodo.11405219

Gomez, S. 2024, Light Curve Fitting v0.10.0, v0.10.0 Zenodo, doi: 10.5281/zenodo.11405219

work page doi:10.5281/zenodo.11405219 2024