REVIEW 3 major objections 4 minor 2 cited by
Red Supergiant problem viewed from the nebular phase spectroscopy of type II supernovae
T0 review · 3 major / 4 minor · reviewed 2026-08-16 · deepseek-v4-flash
Pith's one-line read The paper claims that nebular [O I] spectroscopy of 50 Type II supernovae yields a luminosity distribution for their red supergiant progenitors with an upper cutoff at log L/Lsun = 5.21, making the red supergiant problem statistically…
desk verdict A genuinely new nebular-spectroscopy cross-check on the RSG problem, with an honest but conditional 2–3 sigma claim that rests on faint-end completeness and a 12-SN calibration. 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 load-bearing object is the fractional [O I] flux f[O I] (and its H-alpha-regulated form f[O I]/(1 - f_Halpha)), measured from standardized nebular spectra and compared with single-red-supergiant spectral model tracks for 12, 15, and 19 solar-mass progenitors. Because f[O I] is a relative flux, it is insensitive to distance, flux calibration, and moderate extinction. The authors convert f[O I] into a nebular ZAMS mass, then use the overlap between nebular spectroscopy and pre-SN imaging to build an empirical mass–luminosity relation, deliberately avoiding code-dependent oxygen-mass-to-luminosity conversions that scatter by roughly 0.2 dex. They show the inferred luminosity distribution is invariant under affine reparameterizations of the nebular mass scale, provided the transformed masses stay within 9–25 solar masses, which is what makes the upper luminosity cutoff robust to spectral-model and initial-condition uncertainties.
What would settle it
A single Type II supernova with a securely measured progenitor luminosity above log L/Lsun = 5.5 (equivalent to a ZAMS mass above about 25 solar masses) whose nebular [O I] flux also places it above the 19-solar-mass track would contradict the claimed upper cutoff. A less demanding check is to recompute the 12-object calibration using multi-band pre-SN luminosities that correct the single-band underestimates discussed for some red supergiants; if the corrected relation pushes the fitted upper cutoff above 5.5, or moves the 99.8th percentile above 5.44, the reported deficit disappears.
Extended reading notes
Core claim
Using the fractional flux of the nebular [O I] doublet relative to the 5000–8500 Angstrom spectrum, the authors assign each of 50 Type II supernovae a zero-age main-sequence mass distribution, combining two limiting measurements: the raw fractional flux and the same quantity with the H-$\alpha$ line removed. They calibrate the transformation from this spectroscopically inferred mass to red supergiant luminosity on 12 supernovae with pre-SN images, obtaining a strong rank correlation after excluding one outlier, then apply it to the full sample. The resulting luminosity distribution, fit with a bounded power law dN/dlogL proportional to L^(1+Gamma_L), has an upper cutoff log Lup = 5.21 (+0.09, -0.07), implying that the lack of progenitors above log L = 5.5 is significant at 2–3 $\sigma$. No individual object has median log L above 5.5, and the brightest inferred progenitor is at 5.33 (+0.21, -0.18). Under the single-red-supergiant assumption and the KEPLER mass–luminosity relation, this cutoff corresponds to an upper ZAMS mass of 20.63 (+2.42, -1.64) solar masses, consistent with independent upper limits near 18–23 solar masses from pre-SN imaging and plateau light-curve modeling.
Load-bearing premise
The whole argument rests on the assumption that the fractional [O I] flux from the adopted single-red-supergiant nebular models tracks oxygen mass, and therefore ZAMS mass, monotonically, and that the mass–luminosity relation fitted with only twelve overlapping objects—whose pre-SN luminosities are taken at face value—represents the entire Type II supernova population.
Editorial extensions
If this is right
- A hard upper luminosity cutoff near log L = 5.2 implies that stars above roughly 20–25 solar masses rarely die as Type II supernovae with intact hydrogen envelopes.
- The consistency among nebular spectroscopy, pre-SN imaging, and plateau light-curve modeling narrows the allowed explanation to physics that removes or quenches the most massive red supergiants: failed explosions, eruptive mass loss, or binary stripping.
- The H-alpha-regulated form of the [O I] fractional flux provides a route to use nebular spectroscopy even for progenitors with partially stripped envelopes or circumstellar interaction, since it removes the most contaminated spectral line.
- Because the [O I] fractional flux is distance- and extinction-independent, the method can be extended to larger samples from current and future transient surveys without requiring deep pre-SN archival images for every event.
- If the cutoff is physical, searches for failed supernovae or disappearing massive stars should find them preferentially in the 20–30 solar-mass range, and the rate of such events should roughly match the missing fraction implied by the luminosity function.
Reading between the lines
- If the cutoff reflects explodability rather than mass loss, surveys for disappearing stars should recover a missing fraction of Type II progenitors concentrated just above about 20 solar masses; the paper does not predict this rate, but its luminosity function quantifies the gap.
- The invariance of log L under affine transformations of the nebular mass scale suggests that future improvements to nebular modeling will shift the inferred masses without moving the luminosity cutoff; reanalysis with new model grids would test this directly.
- Because the calibration rests on pre-SN luminosities for only 12 objects, a multi-band bolometric campaign for a handful of future nearby Type II supernovae would either harden or dissolve the reported 2–3 sigma significance.
- The same fractional-flux technique could be applied to stripped-envelope or superluminous supernovae that show oxygen nebular lines, but it would need an independent mass–luminosity calibration for those classes.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This paper re-assesses the red supergiant (RSG) problem using nebular-phase spectroscopy of 50 Type II supernovae. The authors measure the fractional flux of [O I] lambda lambda 6300,6363 relative to the integrated 5000-8500 A spectrum, compare it with the Jerkstrand et al. (2012, 2014) models to infer MZAMS,neb for each object, and then convert to progenitor luminosity using an empirically calibrated MZAMS,neb-logL relation based on 12 SNe with pre-SN imaging (after excluding SN 2013ej). The resulting luminosity distribution is fitted with a bounded power law via an emcee Monte Carlo procedure, yielding logLup = 5.21^{+0.09}_{-0.07} and a claimed 2-3 sigma significance for the RSG problem. The paper also compares this result with upper mass cutoffs from plateau light-curve modeling and pre-SN imaging, concluding that the consistency across methods suggests a real physical problem.
Significance. If the central claim is robust, this paper provides a valuable independent probe of the RSG problem with a sample roughly twice as large as previous direct-imaging studies, using a qualitatively different diagnostic (nebular [O I] emission) and a carefully propagated Monte Carlo uncertainty treatment. The affine-invariance robustness test in Section 4.3 is a genuine strength: it demonstrates that the inferred luminosities are insensitive to a large family of transformations of MZAMS,neb. The paper is also commendably transparent about its limitations, including the non-monotonic behavior of M9 models, the arbitrariness of the pseudo-SN completeness correction, and the fact that its own bright-only completeness test reduces the claimed significance below 1 sigma. Because the paper ships enough detail to reproduce the statistical machinery and explicitly compares with multiple independent methods, it is a useful contribution to the RSG problem literature, provided the significance claim is brought in line with the robustness tests.
major comments (3)
- [Section 5, 'Excluding Low-Luminosity Progenitors'] The paper's own robustness test excluding progenitors with logL < 4.6 (N = 33) yields logLup = 5.25^{+0.26}_{-0.12} and the text explicitly states that the significance of the RSG problem is reduced to below 1 sigma. This directly contradicts the abstract and Section 5 headline that the RSG problem is significant at the 2-3 sigma level, and it shows that the headline significance is carried by the assumed treatment of the faint end. Because the nebular spectroscopy sample has no quantified selection function (e.g., [O I] flux sensitivity versus distance and host extinction), the 2-3 sigma claim is not secured. Please either add a quantitative selection model or rephrase the central claim to reflect the sensitivity of the significance to the faint-end completeness assumption.
- [Section 4.2, Table 1; Section 4.3] The empirical MZAMS,neb-logL relation that sets the entire luminosity scale is calibrated on only 12 objects after excluding SN 2013ej. The exclusion is justified by an energy argument and by reference to a forthcoming work, rather than by a quantitative model of the systematic uncertainty; and the pre-SN luminosities are mostly from Davies & Beasor (2018), which is disputed by Healy et al. (2024) and Beasor et al. (2025) as potentially underestimating luminosities through single-band photometry. The affine-transform robustness test in Section 4.3 does not address this concern because it keeps the pre-SN luminosity measurements fixed while transforming MZAMS. Please show that logLup is stable under a plausible systematic shift of the calibration luminosities, or quantify and propagate the bolometric-correction systematics into the LDF fit.
- [Section 3, mass assignment below M12; Section 5, pseudo SNe] Objects with f[O I] below the M12 track are assigned a uniform 10-12 M_sun distribution with a 1 M_sun Gaussian tail, and the pseudo-SN completeness correction in Section 5 is, in the authors' own words, 'somewhat arbitrary.' The M9-model comparison in Figure 4 shows that the f[O I]-MZAMS relation is non-monotonic in this regime, so the assigned distribution is not calibrated to the data. Since the fiducial 2-3 sigma significance is recovered only when pseudo SNe are added (Npseudo up to 30), the significance statement rests on an unmodelled completeness correction. Please replace the pseudo-SN prescription with a selection function derived from the [O I] flux sensitivity of the surveys used, or provide a sensitivity analysis over a plausible range of missing-object luminosity distributions.
minor comments (4)
- [Section 2] The text says 'Figure 1 illustrates this fitting procedure using SNe 2014G and 2023ixf as examples,' but the multi-Gaussian line fitting is shown in Figure 3, not Figure 1.
- [Figure 3 caption] The word 'psuedo-continuum' in the caption should be 'pseudo-continuum.'
- [Equation (6)] The notation dN/dlogL proportional to L^{1+Gamma_L} should clarify that L denotes the linear luminosity in solar units, since the fit parameters and the text are quoted in logL; as written, the functional form is ambiguous.
- [Section 3] The subscript in f[O I],reg is typeset inconsistently, with 'f[O,I],reg' appearing in at least one place; please standardize the notation.
Circularity Check
No significant circularity: the luminosity cutoff is derived from nebular [O I] masses and an observation-calibrated mass-luminosity relation, not fitted to the pre-SN luminosities that define the RSG problem.
full rationale
The derivation chain is self-contained and independent of the quantity it claims to predict. The paper measures fractional [O I] fluxes from nebular spectra, converts them to MZAMS,neb using external spectral models (Jerkstrand et al. 2012, 2014), and then calibrates an empirical MZAMS,neb-logL relation using a small overlapping sample with pre-SN imaging luminosities. This calibrated relation is applied to the full 50-SN sample to produce the luminosity distribution, whose upper cutoff is then fitted with a power law. The central claim, logLup = 5.21, is not an input to the calibration: the full-sample MZAMS,neb distribution is derived purely from [O I] spectroscopy, and the paper explicitly shows that no object sits above the M19 track, so the absence of luminous progenitors is not constructed by the luminosity calibration. The robustness tests with affine transformations of MZAMS,neb further show that the inferred logL values and the cutoff are stable, indicating that the result does not reduce to the choice of calibration. The self-citations (e.g., Fang et al. 2025a) are not load-bearing for the upper cutoff; the exclusion of SN 2013ej is justified by external energy arguments and by the correlation analysis, and removing it does not by construction force the final cutoff. The acknowledged completeness concerns and the reduced significance when low-luminosity progenitors are excluded are statistical robustness issues, not circularity. No step was found where a parameter fitted to the outcome is renamed as a prediction, or where a model assumption is imported solely from the authors' prior work. The analysis therefore contains no significant circular component.
Assumptions & free parameters
free parameters (5)
- power-law slope Gamma_L =
-0.89 (+0.36, -0.38)
- lower luminosity cutoff log Llow =
4.28 (+0.09, -0.11)
- upper luminosity cutoff log Lup =
5.21 (+0.09, -0.07)
- MZAMS distribution for objects below M12 track =
uniform 10-12 Msun plus Gaussian tail with sigma=1 Msun
- pseudo-continuum scatter allowance in Monte Carlo =
20% (0.08 dex)
assumptions (5)
- domain assumption The [O I] lambda 6300,6363 flux is a monotone tracer of oxygen mass and hence MZAMS for SNe II.
- domain assumption The Jerkstrand et al. (2012, 2014) nebular models represent the observed SNe II sample.
- domain assumption The MHe core - logL relation is universal across stellar evolution codes (Eq. 2).
- domain assumption The empirical MLR derived from 12 overlapping SNe is representative of all 50 SNe.
- domain assumption The nebular spectroscopy sample is representative of the SNe II population, with completeness that can be approximated by adding pseudo SNe.
invented entities (1)
-
Pseudo SNe
Cite this review
Pith. "Pith review of Red Supergiant problem viewed from the nebular phase spectroscopy of type II supernovae." pith.science (2026). https://pith.science/paper/IGBHLT7Q
@misc{pith2026250414502,
author = {Pith},
title = {Pith review of: Red Supergiant problem viewed from the nebular phase spectroscopy of type II supernovae},
year = {2026},
howpublished = {\url{https://pith.science/paper/IGBHLT7Q}},
note = {Machine review of arXiv:2504.14502}
}
abstract
The red supergiant (RSG) problem refers to the observed dearth of luminous RSGs identified as progenitors of Type II supernovae (SNe II) in pre-SN imaging. Understanding this phenomenon is essential for studying pre-SN mass loss and the explodability of core-collapse SNe. In this work, we re-assess the RSG problem using late-phase spectroscopy of a sample of 50 SNe II. The [O I] $\lambda\lambda$6300,6363 emission in the spectra is employed to infer the zero-age main sequence (ZAMS) mass distribution of the progenitors, which is then transformed into a luminosity distribution via an observation-calibrated mass-luminosity relation. The resulting luminosity distribution reveals an upper cutoff at log $L/L_{\odot} = 5.21^{+0.09}_{-0.07}$ dex, and the RSG problem is statistically significant at the 2$\sigma$ to 3$\sigma$ level. Assuming single RSG progenitors that follow the mass-luminosity relation of KEPLER models, this luminosity cutoff corresponds to an upper ZAMS mass limit of $20.63^{+2.42}_{-1.64}$ $M_{\odot}$. Comparisons with independent measurements, including pre-SN imaging and plateau-phase light curve modeling, consistently yield an upper ZAMS mass limit below about 25 $M_{\odot}$, with a significance level of 1-3$\sigma$. While each individual method provides only marginal significance, the consistency across multiple methodologies suggests that the lack of luminous RSG progenitors may reflect a genuine physical problem. Finally, we discuss several scenarios to account for this issue should it be confirmed as a true manifestation of stellar physics.
Figures
Figures from the paper (10 more)
Forward citations
Cited by 2 Pith papers
-
SN 2022acko and the Properties of its Red Supergiant Progenitor: Direct Detection, Light Curves, and Nebular Spectroscopy
The progenitor mass of SN 2022acko inferred from pre-explosion images (7.5 Msun) disagrees with masses from light-curve and spectral modeling (9-15 Msun), with the tension likely caused by model and calibration systematics.
-
SN 2022xus: bridging the gap between Type IIP and IIL supernovae
SN 2022xus is a transitional Type II supernova with a 94.8-day plateau, a decline rate of 1.23 mag per 100 days, mixed IIP/IIL spectral features, and a likely 12-15 solar-mass progenitor.
Reference graph
Works this paper leans on
-
[1]
doi:10.3847/1538-4357/aae7c9 Eldridge, J. J. & Vink, J. S. 2006, A&A, 452, 295. doi:10.1051/0004-6361:20065001 Eldridge, J. J., Izzard, R. G., & Tout, C. A. 2008, MNRAS, 384, 1109. doi:10.1111/j.1365-2966.2007.12738.x Eldridge, J. J., Fraser, M., Smartt, S. J., et al. 2013, MNRAS, 436, 774. doi:10.1093/mnras/stt1612 Eldridge, J. J., Xiao, L., Stanway, E. ...
arXiv 2006
-
[3]
doi:10.3847/1538-4357/ab22b6 Goldberg, J. A., Bildsten, L., & Paxton, B. 2020, ApJ, 891,
-
[5]
doi:10.1088/0004-637X/797/1/5 Zhao, Z., Zhang, J., Li, L., et al. 2024, ApJ, 973, 155. doi:10.3847/1538-4357/ad5fe8
-
[10]
doi:10.3847/1538-4357/aa6afe Yuan, F., Jerkstrand, A., Valenti, S., et al. 2016, MNRAS, 461, 2003. doi:10.1093/mnras/stw1419 Zapartas, E., de Mink, S. E., Justham, S., et al. 2019, A&A, 631, A5. doi:10.1051/0004-6361/201935854 Zapartas, E., de Mink, S. E., Justham, S., et al. 2021, A&A, 645, A6. doi:10.1051/0004-6361/202037744 Zapartas, E., de Wit, S., An...
-
[15]
doi:10.3847/1538-4357/ab7205 Guillochon, J., Parrent, J., Kelley, L. Z., et al. 2017, ApJ, 835, 64. doi:10.3847/1538-4357/835/1/64 Gurugubelli, U. K., Sahu, D. K., Anupama, G. C., et al. 2008, Bulletin of the Astronomical Society of India, 36, 79 Guti´ errez, C. P., Anderson, J. P., Hamuy, M., et al. 2017, ApJ, 850, 89. doi:10.3847/1538-4357/aa8f52 Guti´ ...
-
[19]
doi:10.3847/1538-4357/acb8b3 Tak´ ats, K., Pumo, M. L., Elias-Rosa, N., et al. 2014, MNRAS, 438, 368. doi:10.1093/mnras/stt2203 Tak´ ats, K., Pignata, G., Pumo, M. L., et al. 2015, MNRAS, 450, 3137. doi:10.1093/mnras/stv857 Teja, R. S., Singh, A., Sahu, D. K., et al. 2022, ApJ, 930,
-
[34]
doi:10.3847/1538-4357/ac610b Teja, R. S., Singh, A., Sahu, D. K., et al. 2023, ApJ, 954,
-
[36]
doi:10.3847/1538-4357/ad8d5a Faran, T., Poznanski, D., Filippenko, A. V., et al. 2014, MNRAS, 442, 844. doi:10.1093/mnras/stu955 Ferrari, L., Folatelli, G., Ertini, K., et al. 2024, A&A, 687, L20. doi:10.1051/0004-6361/202450440 Filippenko, A. V. 1997, ARA&A, 35, 309. doi:10.1146/annurev.astro.35.1.309 22 Folatelli, G., Gonzalez, S., & Morrell, N. 2007, C...
Show all 20 references
-
[61]
J., Subrayan, B
doi:10.3847/1538-4357/ab0d88 Moriya, T. J., Subrayan, B. M., Milisavljevic, D., et al. 2023, PASJ, 75, 634. doi:10.1093/pasj/psad024 Morozova, V., Piro, A. L., & Valenti, S. 2018, ApJ, 858, 15. doi:10.3847/1538-4357/aab9a6 M¨ uller, B., Heger, A., Liptai, D., et al. 2016, MNRAS, 460,
2023 doi
-
[93]
& Adams, S
doi:10.3847/1538-4357/aac2da Sukhbold, T. & Adams, S. 2020, MNRAS, 492, 2578. doi:10.1093/mnras/staa059 Sun, N.-C., Maund, J. R., & Crowther, P. A. 2023, MNRAS. doi:10.1093/mnras/stad690 Takahashi, K. 2018, ApJ, 863, 153. doi:10.3847/1538-4357/aad2d2 Takahashi, K. & Langer, N....
2020 doi
-
[94]
A., et al
doi:10.3847/1538-4357/ac6ac9 Gal-Yam, A., Bufano, F., Barlow, T. A., et al. 2008, ApJL, 685, L117. doi:10.1086/592744 Gal-Yam, A. 2017, Handbook of Supernovae, 195. doi:10.1007/978-3-319-21846-5 35 G´ omez, G. & L´ opez, R. 2000, AJ, 120, 367. doi:10.1086/301419 Goldberg, J. A...
2008 doi
-
[117]
S., Milisavljevic, D., Margutti, R., et al
doi:10.3847/1538-4357/ad8f3f Black, C. S., Milisavljevic, D., Margutti, R., et al. 2017, ApJ, 848, 5. doi:10.3847/1538-4357/aa8999 Blanton, E. L., Schmidt, B. P., Kirshner, R. P., et al. 1995, AJ, 110, 2868. doi:10.1086/117735 Bose, S., Kumar, B., Sutaria, F., et al. 2013, MNRAS, 433,
2017 doi
-
[124]
E., Sukhbold, T., et al
doi:10.3847/0004-637X/818/2/124 Ertl, T., Woosley, S. E., Sukhbold, T., et al. 2020, ApJ, 890, 51. doi:10.3847/1538-4357/ab6458 Ercolino, A., Jin, H., Langer, N., et al. 2023, arXiv:2308.01819. doi:10.48550/arXiv.2308.01819 Fang, Q., Maeda, K., Kuncarayakti, H., et al. 2019, N...
-
[139]
2018, MNRAS, 475, 3959
doi:10.3847/0004-637X/832/2/139 Huang, F., Wang, X.-F., Hosseinzadeh, G., et al. 2018, MNRAS, 475, 3959. doi:10.1093/mnras/sty066 Inserra, C., Pastorello, A., Turatto, M., et al. 2013, A&A, 555, A142. doi:10.1051/0004-6361/201220496 Itagaki, K., Noguchi, T., Nakano, S., et al....
2018
-
[155]
S., Goldberg, J
doi:10.3847/1538-4357/acdf5e Teja, R. S., Goldberg, J. A., Sahu, D. K., et al. 2024, ApJ, 974, 44. doi:10.3847/1538-4357/ad67d9 24 Temaj, D., Schneider, F. R. N., Laplace, E., et al. 2024, A&A, 682, A123. doi:10.1051/0004-6361/202347434 Terreran, G., Jerkstrand, A., Benetti, S...
2024 doi
-
[615]
2024, arXiv:2412.04386
doi:10.1086/322450 Healy, S., Horiuchi, S., & Ashall, C. 2024, arXiv:2412.04386. doi:10.48550/arXiv.2412.04386 Heger, A., Fryer, C. L., Woosley, S. E., et al. 2003, ApJ, 591, 288. doi:10.1086/375341 Hendry, M. A., Smartt, S. J., Maund, J. R., et al. 2005, MNRAS, 359, 906. doi:...
-
[742]
E., Guti´ errez, C
doi:10.1093/mnras/stw1083 M¨ uller-Bravo, T. E., Guti´ errez, C. P., Sullivan, M., et al. 2020, MNRAS, 497, 361. doi:10.1093/mnras/staa1932 Murai, Y., Tanaka, M., Kawabata, M., et al. 2024, MNRAS, 528, 4209. doi:10.1093/mnras/stae170 Nagao, T., Maeda, K., Mattila, S., et al. 2...
2020
-
[940]
2015, PASA, 32, e015
doi:10.1088/0004-637X/725/1/940 Yoon, S.-C. 2015, PASA, 32, e015. doi:10.1017/pasa.2015.16 Yoon, S.-C., Dessart, L., & Clocchiatti, A. 2017, ApJ, 840,
2015 doi
-
[1871]
2019, ApJL, 873, L3
doi:10.1093/mnras/stt864 Bose, S., Dong, S., Elias-Rosa, N., et al. 2019, ApJL, 873, L3. doi:10.3847/2041-8213/ab0558 Bostroem, K. A., Valenti, S., Horesh, A., et al. 2019, MNRAS, 485, 5120. doi:10.1093/mnras/stz570 Burrows, A. & Vartanyan, D. 2021, Nature, 589, 29. doi:10.103...
-
[2054]
2021, ApJ, 912, 112
doi:10.1111/j.1365-2966.2011.19860.x Wang, T., Jiang, B., Ren, Y., et al. 2021, ApJ, 912, 112. doi:10.3847/1538-4357/abed4b Yang, M., Bonanos, A. Z., Jiang, B., et al. 2023, A&A, 676, A84. doi:10.1051/0004-6361/202244770 Yaron, O. & Gal-Yam, A. 2012, PASP, 124, 668. doi:10.108...
2011
Reviewed August 16, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.