Recognition: unknown
Type Ib Supernovae are bluer than Type Ic Supernovae
Pith reviewed 2026-05-09 19:05 UTC · model grok-4.3
The pith
Type Ib supernovae are bluer than Type Ic supernovae in optical colors.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
We find a systematic difference in their optical colors: SNe Ib are, on average, bluer than SNe Ic at a statistically significant level. This difference appears intrinsic, likely reflecting progenitors with different degrees of stripping -- helium-rich for SNe Ib and helium-poor for SNe Ic. In addition, we find that SNe Ib/Ic with narrow lines are bluer than those without, which might originate from circumstellar matter interaction.
What carries the argument
The average optical color difference between Type Ib and Type Ic supernovae, serving as a diagnostic for the degree of helium stripping in the progenitor stars.
If this is right
- Colors can be used to probe the stripping history of massive stars even when spectra are unavailable.
- Photometric surveys can classify and study large numbers of stripped supernovae using color information alone.
- The distinction supports separate evolutionary paths for helium-rich and helium-poor progenitors.
- Narrow-lined events being bluer points to circumstellar material as an additional factor shaping their appearance.
Where Pith is reading between the lines
- The finding could supply an observational test for binary versus single-star models of envelope removal.
- It might allow statistical estimates of how often stars retain partial helium layers across different galactic environments.
- Observations in additional wavelength bands could check whether the temperature or composition differences persist beyond optical light.
Load-bearing premise
The color difference must reflect real differences in the progenitors rather than selection effects, dust extinction variations, or misclassification of the supernova types.
What would settle it
A reanalysis that applies uniform host-galaxy extinction corrections and finds the color difference disappears would show the claimed intrinsic difference is not present.
Figures
read the original abstract
Type Ib and Ic supernovae (SNe Ib/Ic) are the bright finale of massive stars that have lost their hydrogen envelopes, making them powerful probes of mass stripping in massive star evolution. The advent of modern large photometric and spectroscopic surveys presents the unique opportunity to investigate systematic differences between these two kinds of SNe. In this study, we analyze a large, homogeneous sample of SNe Ib/Ic light curves from the Zwicky Transient Facility. We find a systematic difference in their optical colors: SNe Ib are, on average, bluer than SNe Ic at a statistically significant level. This difference appears intrinsic, likely reflecting progenitors with different degrees of stripping -- helium-rich for SNe Ib and helium-poor for SNe Ic. In addition, we find that SNe Ib/Ic with narrow lines (SNe Ibn/Icn) are bluer than those without, which might originate from circumstellar matter interaction, with potential connection to fast blue optical transients. We demonstrate that SN colors offer a promising probe of mass stripping in massive stars, potentially providing a useful tool for analyzing large photometric data and improving predictions for the final outcomes of stripped massive stars.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper analyzes a homogeneous sample of Type Ib and Ic supernovae light curves from the Zwicky Transient Facility. It reports a systematic difference in optical colors, with SNe Ib being bluer than SNe Ic on average at a statistically significant level. This offset is interpreted as intrinsic, reflecting different degrees of envelope stripping (helium-rich vs. helium-poor progenitors). The work also finds that narrow-lined SNe Ibn/Icn are bluer than standard Ib/Ic events, possibly due to circumstellar matter interaction, and suggests colors as a probe of mass stripping in massive stars.
Significance. If the color difference is shown to be intrinsic after rigorous checks, the result supplies a new photometric diagnostic for progenitor stripping that could be applied to large survey datasets. The use of a uniform ZTF sample is a clear strength for reducing heterogeneity compared with heterogeneous literature compilations.
major comments (3)
- [Extinction and reddening section] The central claim that the color offset is intrinsic requires explicit demonstration that differential host-galaxy extinction has been ruled out. No tests correlating color with host mass, star-formation rate, or Na I D equivalent width are described, and the extinction law applied is not specified in detail.
- [Sample selection and classification] Classification robustness is load-bearing: the Ib/Ic distinction rests on the presence or absence of He I lines, yet no re-classification exercise with stricter line-strength thresholds or comparison to independent catalogs is presented. Misclassification near the boundary could artificially enhance the reported color difference.
- [Results and statistical analysis] Statistical details are insufficient to evaluate the claimed significance. The manuscript does not report the final sample sizes for Ib and Ic, the precise phase or filter combination used for the color measurement, or the exact test (e.g., Kolmogorov-Smirnov, bootstrap) that yields the reported significance.
minor comments (2)
- [Figures] Figure captions should explicitly state the rest-frame phase at which colors are measured and whether they are corrected for Milky Way extinction only.
- [Abstract and results] The abstract states the difference is 'statistically significant' but the main text should quote the exact p-value or significance level for transparency.
Simulated Author's Rebuttal
We thank the referee for their constructive and detailed report. The comments have prompted us to strengthen the presentation of our results on the intrinsic nature of the color offset, the robustness of classifications, and the statistical methodology. We address each major comment below and indicate the revisions made.
read point-by-point responses
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Referee: [Extinction and reddening section] The central claim that the color offset is intrinsic requires explicit demonstration that differential host-galaxy extinction has been ruled out. No tests correlating color with host mass, star-formation rate, or Na I D equivalent width are described, and the extinction law applied is not specified in detail.
Authors: We agree that additional explicit checks are required to support the claim that the color difference is intrinsic. In the revised manuscript we have added a dedicated subsection on extinction. We now present correlations between the observed colors and host-galaxy stellar mass and star-formation rate drawn from the ZTF host catalog and public surveys. We specify that we adopt the Fitzpatrick (1999) extinction law with R_V = 3.1 for the Milky Way component and discuss the treatment of host extinction. For Na I D, high-resolution spectra are available for only a subset of events; within that subset we find no significant correlation with color. These additions are now included in Section 4.1. revision: yes
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Referee: [Sample selection and classification] Classification robustness is load-bearing: the Ib/Ic distinction rests on the presence or absence of He I lines, yet no re-classification exercise with stricter line-strength thresholds or comparison to independent catalogs is presented. Misclassification near the boundary could artificially enhance the reported color difference.
Authors: We acknowledge that classification accuracy is central to the result. We have performed a re-classification exercise applying stricter equivalent-width thresholds for He I lines and have cross-matched our sample against the ZTF public classification catalog and the Open Supernova Catalog. The color offset remains statistically significant after removal of borderline objects. A summary of the classification criteria and the outcome of the re-classification is now provided in Section 2.2 and Table 1. revision: yes
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Referee: [Results and statistical analysis] Statistical details are insufficient to evaluate the claimed significance. The manuscript does not report the final sample sizes for Ib and Ic, the precise phase or filter combination used for the color measurement, or the exact test (e.g., Kolmogorov-Smirnov, bootstrap) that yields the reported significance.
Authors: We apologize for these omissions. The revised manuscript now states the final sample sizes after all quality cuts, specifies the exact phase and filter combination used for the primary color measurement, and provides a full description of the statistical test (a two-sample Kolmogorov-Smirnov test supplemented by bootstrap resampling). The resulting p-value and methodology are reported in Section 3.2. revision: yes
Circularity Check
No circularity: direct empirical color comparison from survey data
full rationale
The paper conducts a statistical comparison of observed optical colors in a homogeneous ZTF photometric sample of spectroscopically classified SNe Ib and Ic. No equations, fitted parameters, or model predictions are defined in terms of the target color offset and then re-used as evidence for that offset. Classification, extinction handling, and bias checks are presented as data-driven arguments rather than self-referential definitions or load-bearing self-citations that collapse the central result. The derivation chain consists of straightforward measurement and averaging of independent observables, making the analysis self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Supernovae can be reliably classified as Type Ib or Ic from spectra
- domain assumption Optical colors measured from light curves reflect intrinsic supernova properties after standard corrections
Reference graph
Works this paper leans on
-
[1]
Binaries among B2 - B5 IV, V absorption and emission stars. , keywords =. doi:10.1086/190498 , adsurl =
-
[2]
, keywords =
Mode identification of pulsating stars from line-profile variations with the moment method: a more accurate discriminant. , keywords =
-
[3]
, keywords =
Evidence for binarity and multiperiodicity in the beta Cephei star beta Crucis. , keywords =
-
[4]
Ceti Is Not Monoperiodic: Seismic Modeling of a Cephei Star from MOST Space-based Photometry. , keywords =. doi:10.1086/500800 , archivePrefix =. astro-ph/0602036 , primaryClass =
-
[5]
2018, ApJ, 858, 115, doi: 10.3847/1538-4357/aabfc1
Related Progenitor Models for Long-duration Gamma-Ray Bursts and Type Ic Superluminous Supernovae. , keywords =. doi:10.3847/1538-4357/aabfc1 , archivePrefix =. 1804.07317 , primaryClass =
-
[6]
The FORS1 catalogue of stellar magnetic field measurements. , keywords =. doi:10.1051/0004-6361/201526497 , archivePrefix =. 1508.03839 , primaryClass =
-
[7]
2020, MNRAS, 495, 1978, doi: 10.1093/mnras/staa1332
On the origin of the bimodal rotational velocity distribution in stellar clusters: rotation on the pre-main sequence. , keywords =. doi:10.1093/mnras/staa1332 , archivePrefix =. 2005.01779 , primaryClass =
-
[8]
Boron Benchmarks for the Galactic Disk. , keywords =. doi:10.1086/382672 , adsurl =
-
[9]
Boron Depletion in F and G Dwarf Stars and the Beryllium-Boron Correlation. , keywords =. doi:10.1086/427687 , archivePrefix =. astro-ph/0411246 , primaryClass =
-
[10]
Boron in the Small Magellanic Cloud: A Novel Test of Light-Element Production. , keywords =. doi:10.1086/340662 , archivePrefix =. astro-ph/0204026 , primaryClass =
-
[11]
Rotating massive main-sequence stars. I. Grids of evolutionary models and isochrones. , keywords =. 2011 , month = jun, volume =. doi:10.1051/0004-6361/201016113 , archivePrefix =. 1102.0530 , primaryClass =
-
[12]
Rotating massive main-sequence stars. II. Simulating a population of LMC early B-type stars as a test of rotational mixing. , keywords =. 2011b , month = jun, volume =. doi:10.1051/0004-6361/201016114 , archivePrefix =. 1102.0766 , primaryClass =
-
[13]
The Orion OB1 association. I. Stellar content. , keywords =. doi:10.48550/arXiv.astro-ph/9403051 , archivePrefix =. astro-ph/9403051 , primaryClass =
-
[14]
High-resolution spectroscopic study of massive blue and red supergiants in Perseus OB1. I. Definition of the sample, membership, and kinematics. , keywords =. doi:10.1051/0004-6361/202039019 , archivePrefix =. 2008.13299 , primaryClass =
-
[15]
Variability of OB stars from TESS southern Sectors 1-13 and high-resolution IACOB and OWN spectroscopy. , keywords =. doi:10.1051/0004-6361/202037700 , archivePrefix =. 2005.09658 , primaryClass =
-
[16]
2008, , 385, 1053, 10.1111/j.1365-2966.2008.12909.x
Catalogue of averaged stellar effective magnetic fields - II. Re-discussion of chemically peculiar A and B stars. , keywords =. doi:10.1111/j.1365-2966.2008.14227.x , adsurl =
-
[17]
The spectroscopic Hertzsprung-Russell diagram of Galactic massive stars. , keywords =. doi:10.1051/0004-6361/201425028 , archivePrefix =. 1410.3499 , primaryClass =
-
[18]
The. ApJ , author =. 2018 , pages =. doi:10.3847/1538-4357/aae6d0 , language =
-
[19]
2016, The Astrophysical Journal, 823, 102, doi: 10.3847/0004-637X/823/2/102
ApJ , author =. 2016 , pages =. doi:10.3847/0004-637X/823/2/102 , language =
work page internal anchor Pith review doi:10.3847/0004-637x/823/2/102 2016
-
[20]
The dependence of convective core overshooting on stellar mass. , keywords =. doi:10.1051/0004-6361/201628779 , adsurl =
-
[21]
The Astrophysical Journal , author =
Chemical. The Astrophysical Journal , author =. 1994 , note =. doi:10.1086/174053 , urldate =
-
[22]
A. ApJ , author =. 1999 , pages =. doi:10.1086/306796 , language =
-
[23]
A Uniform Analysis of Boron in F and G Disk Dwarfs fromHubble Space Telescope Archival Spectra. , keywords =. doi:10.1086/308415 , adsurl =
-
[24]
Boron abundances in the. Proc. IAU , author =. 2009 , pages =. doi:10.1017/S1743921310004199 , language =
-
[25]
, keywords =
COMPTEL observations of Galactic \^26\^Al emission. , keywords =
-
[26]
The. A&A , author =. 2006 , pages =. doi:10.1051/0004-6361:20065392 , language =
-
[27]
Asteroseismology of the Cep star HD 129929. II. Seismic constraints on core overshooting, internal rotation and stellar parameters. , keywords =. doi:10.1051/0004-6361:20034143 , adsurl =
-
[28]
The. A&A , author =. 2013 , pages =. doi:10.1051/0004-6361/201220273 , language =
-
[29]
Publications of the Dominion Astrophysical Observatory Victoria , year = 1960, month = jan, volume =
The spectroscopic orbit of nu Ori. Publications of the Dominion Astrophysical Observatory Victoria , year = 1960, month = jan, volume =
1960
-
[30]
2008, Ap&SS, 316, 43, doi: 10.1007/s10509-007-9511-y
The. Astrophys Space Sci , author =. 2008 , pages =. doi:10.1007/s10509-007-9511-y , language =
-
[31]
The Astrophysical Journal , author =
Aproximations to the radii of Roche lobes. , keywords =. doi:10.1086/160960 , adsurl =
-
[32]
Grids of stellar models with rotation:. A&A , author =. 2012 , pages =. doi:10.1051/0004-6361/201117751 , language =
-
[33]
The. A&A , author =. 2005 , pages =. doi:10.1051/0004-6361:20042446 , language =
-
[34]
The. A&A , author =. 2006 , pages =. doi:10.1051/0004-6361:20064988 , language =
-
[35]
Evidence of Tidal Effects in Some Pulsating Stars. II. Lacertae and Cephei. , year = 1969, month = oct, volume =. doi:10.1086/150190 , adsurl =
-
[36]
B fields in OB stars (BOB): Low-resolution FORS2 spectropolarimetry of the first sample of 50 massive stars. , keywords =. doi:10.1051/0004-6361/201526725 , archivePrefix =. 1508.00750 , primaryClass =
-
[37]
Evidence of magnetic field decay in massive main-sequence stars. , keywords =. doi:10.1051/0004-6361/201628259 , archivePrefix =. 1606.07599 , primaryClass =
-
[38]
The. A&A , author =. 2005 , pages =. doi:10.1051/0004-6361:20041527 , language =
-
[39]
Constraints on rotational mixing from surface evolution of light elements in massive stars , volume =. A&A , author =. 2010 , pages =. doi:10.1051/0004-6361/201014340 , language =
-
[40]
Summary of the contents and survey properties
Gaia Early Data Release 3. Summary of the contents and survey properties. , keywords =. doi:10.1051/0004-6361/202039657 , archivePrefix =. 2012.01533 , primaryClass =
-
[41]
Georgy, Cyril and Ekström, Sylvia and Granada, Anahí and Meynet, Georges and Mowlavi, Nami and Eggenberger, Patrick and Maeder, André , year =. Populations of rotating stars. -. doi:10.48550/ARXIV.1303.2321 , urldate =
-
[42]
Carbon, nitrogen, and oxygen abundances in early. ApJ , author =. 1992 , pages =. doi:10.1086/171116 , language =
-
[43]
Monthly Notices of the Royal Astronomical Society , author =
Effects of winds on the leftover hydrogen in massive stars following. Monthly Notices of the Royal Astronomical Society , author =. 2019 , pages =. doi:10.1093/mnras/stz1134 , language =
-
[44]
The. A&A , author =. 2017 , pages =. doi:10.1051/0004-6361/201629225 , language =
-
[45]
Groh, J. H. and Ekström, S. and Georgy, C. and Meynet, G. and Choplin, A. and Eggenberger, P. and Hirschi, R. and Maeder, A. and Murphy, L. J. and Boian, I. and Farrell, E. J. , month = jul, year =. Grids of stellar models with rotation. Astronomy & Astrophysics, Volume 627, id.A24,. doi:10.1051/0004-6361/201833720 , language =
-
[46]
The MiMeS survey of Magnetism in Massive Stars: magnetic analysis of the O-type stars. , keywords =. doi:10.1093/mnras/stw2743 , archivePrefix =. 1610.07895 , primaryClass =
-
[47]
A comprehensive analysis of the WN class
The Wolf-Rayet stars in the Large Magellanic Cloud. A comprehensive analysis of the WN class. , keywords =. doi:10.1051/0004-6361/201322696 , archivePrefix =. 1401.5474 , primaryClass =
-
[48]
The Galactic WN stars. Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation. , keywords =. doi:10.1051/0004-6361:20065052 , archivePrefix =. astro-ph/0608078 , primaryClass =
-
[49]
Internal circulation in tidally locked massive binary stars: Consequences for double black hole formation. , keywords =. 2020a , month = sep, volume =. doi:10.1051/0004-6361/202038499 , archivePrefix =. 2007.11299 , primaryClass =
-
[50]
Stringent upper limit on. A&A , author =. 2021 , pages =. doi:10.1051/0004-6361/202141269 , language =
-
[51]
Presupernova Evolution of Differentially Rotating Massive Stars Including Magnetic Fields. , keywords =. doi:10.1086/429868 , archivePrefix =. astro-ph/0409422 , primaryClass =
-
[52]
Discovery of the magnetic field in the pulsating B star Cephei. , keywords =. doi:10.1051/0004-6361/201321584 , archivePrefix =. 1305.2601 , primaryClass =
-
[53]
, year = 1980, month = dec, volume =
The spectroscopic binary gam1 Vel. , year = 1980, month = dec, volume =. doi:10.1086/130756 , adsurl =
-
[54]
Massive star evolution: rotation, winds, and overshooting vectors in the mass-luminosity plane. I. A calibrated grid of rotating single star models. , keywords =. doi:10.1051/0004-6361/201834123 , archivePrefix =. 1811.12190 , primaryClass =
-
[55]
A. ApJ , author =. 2010 , pages =. doi:10.1088/0004-637X/722/1/605 , language =
-
[56]
The VLT-FLAMES survey of massive stars: surface chemical compositions of B-type stars in the Magellanic Clouds. , keywords =. doi:10.1051/0004-6361:20066148 , archivePrefix =. astro-ph/0609710 , primaryClass =
-
[57]
The. ApJ , author =. 2008 , pages =. doi:10.1086/587436 , language =
-
[58]
The VLT-FLAMES survey of massive stars: constraints on stellar evolution from the chemical compositions of rapidly rotating Galactic and Magellanic Cloud B-type stars. , keywords =. doi:10.1051/0004-6361/200809925 , archivePrefix =. 0901.3853 , primaryClass =
-
[59]
Light Elements in the Universe , year = 2010, editor =
Observations of light elements in massive stars. Light Elements in the Universe , year = 2010, editor =. doi:10.1017/S1743921310004291 , adsurl =
-
[60]
Nitrogen chronology of massive main sequence stars. , keywords =. doi:10.1051/0004-6361/201118352 , archivePrefix =. 1206.4146 , primaryClass =
-
[61]
Induced differential rotation and mixing in asynchronous binary stars. , keywords =. doi:10.1051/0004-6361/202039369 , archivePrefix =. 2107.09190 , primaryClass =
-
[62]
Tracing the young massive high-eccentricity binary system \^1Orionis C through periastron passage. , keywords =. doi:10.1051/0004-6361/200810368 , archivePrefix =. 0902.0365 , primaryClass =
-
[63]
Massive Stars as Cosmic Engines , year = 2008, editor =
Rotation and Massive Close Binary Evolution. Massive Stars as Cosmic Engines , year = 2008, editor =. doi:10.1017/S1743921308020462 , archivePrefix =. 0803.0621 , primaryClass =
-
[64]
Light Elements in the Universe , year = 2010, editor =
Light elements in massive single and binary stars. Light Elements in the Universe , year = 2010, editor =. doi:10.1017/S1743921310004540 , archivePrefix =. 1003.1575 , primaryClass =
-
[65]
2012, ARA&A, 50, 107, doi: 10.1146/annurev-astro-081811-125534
Presupernova Evolution of Massive Single and Binary Stars. , keywords =. doi:10.1146/annurev-astro-081811-125534 , archivePrefix =. 1206.5443 , primaryClass =
-
[66]
The spectroscopic. A&A , author =. 2014 , pages =. doi:10.1051/0004-6361/201423374 , language =
-
[67]
Properties of OB star-black hole systems derived from detailed binary evolution models. , keywords =. doi:10.1051/0004-6361/201937375 , archivePrefix =. 1912.09826 , primaryClass =
-
[68]
A Grid of NLTE Line-blanketed Model Atmospheres of Early B-Type Stars. , keywords =. doi:10.1086/511270 , archivePrefix =. astro-ph/0611891 , primaryClass =
-
[69]
A new analysis of the radial velocity variations of the eclipsing and spectroscopic binary. A&A , author =. 2001 , pages =. doi:10.1051/0004-6361:20000344 , language =
-
[70]
, keywords =
Orbital elements of binary systems with a chemically peculiar star. , keywords =
-
[71]
Stellar Multiplicity in the Scorpius-Centaurus Association. , keywords =. doi:10.1086/191204 , adsurl =
-
[72]
The new orbital elements and properties of ɛ Persei. , keywords =. doi:10.1051/0004-6361:20053032 , adsurl =
-
[73]
The Variable Velocity of Theta Carinae. , keywords =. doi:10.1086/133658 , adsurl =
-
[74]
A. AJ , author =. 2022 , pages =. doi:10.3847/1538-3881/ac35e2 , language =
-
[75]
, year = 1936, month = jul, volume =
A Rediscussion of the Orbits of Seventy-Seven Spectroscopic Binaries. , year = 1936, month = jul, volume =. doi:10.1086/143751 , adsurl =
-
[76]
Astronomicheskii Zhurnal , author =
The binary system. Astronomicheskii Zhurnal , author =. 1997 , note =
1997
-
[77]
New Astronomy Reviews , author =
Chemical enrichments by massive stars and the effects of rotation , volume =. New Astronomy Reviews , author =. 2000 , pages =. doi:10.1016/S1387-6473(00)00051-8 , language =
-
[78]
The impact of tides and mass transfer on the evolution of metal-poor massive binary stars
-
[79]
The role of mass transfer and common envelope evolution in the formation of merging binary black holes , volume =. A&A , author =. 2021 , pages =. doi:10.1051/0004-6361/202039992 , language =
-
[80]
Stellar evolution with rotation. V. Changes in all the outputs of massive star models. , keywords =. doi:10.48550/arXiv.astro-ph/0006404 , archivePrefix =. astro-ph/0006404 , primaryClass =
discussion (0)
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