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SN 2023gfo: A Peculiar Type IIP Supernova with High Luminosity and Normal Plateau Duration

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ReviewThe objections and verdict, as JSON Paper breakdownThe authors' claims, conditions and measurements, as JSON Signed receiptProof this review has not been altered
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Riko Namba, Masayuki Yamanaka, Keiichi Maeda, Avinash Singh, Kenta Taguchi, Takahiro Nagayama, Miho Kawabata, Koji S. Kawabata
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Tatsuya Nakaoka, Devendra Sahu, Anjasha Gangopadhyay, G. C. Anupama

High Energy Astrophysical Phenomena · Submitted 17 Aug 2026 · 73 references

Pith's verdict: Solid new data for a luminous Type IIP, but the inflated-progenitor radius depends on an extinction assumption that could easily halve the quoted value.

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arXiv ID2608.16006 (version 1)
Pith IDTDJA4YIX, Pith's permanent record of this paper and its review
CitationAnjasha Gangopadhyay, Avinash Singh, Devendra Sahu, G. C. Anupama, Keiichi Maeda, Kenta Taguchi, Koji S. Kawabata, Masayuki Yamanaka, Miho Kawabata, Riko Namba, Takahiro Nagayama, Tatsuya Nakaoka. "SN 2023gfo: A Peculiar Type IIP Supernova with High Luminosity and Normal Plateau Duration." arXiv:2608.16006 (2026). https://pith.science/paper/TDJA4YIX
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The paper

The paper claims

SN 2023gfo reached $M_V=-18.6$ mag with a normal 108-day plateau, and analytic scaling relations imply a pre-explosion progenitor radius near $3{,}300\,R_\odot$, pointing to substantial envelope inflation before collapse.

The reading

SN 2023gfo, a Type IIP supernova in NGC 4995 at 26.4 Mpc, reached a peak absolute magnitude of $M_V = -18.6$ mag and a quasi-bolometric luminosity of $(5.9 \pm 1.5)\times10^{42}$ erg s$^{-1}$, putting it at the very bright end of the Type IIP population. Its plateau, however, lasted a normal $108 \pm 8$ days, and its early H$\alpha$ absorption velocity of about 13,800 km s$^{-1}$ is among the highest seen in Type IIP SNe. The paper uses this combination to infer, via hydrogen-recombination plateau scaling relations, a pre-supernova radius of about $3{,}300 \pm 500\,R_\odot$---several times larger than ordinary red supergiants---with roughly normal explosion energy and ejecta mass. It argues that the most plausible origin is an inflated envelope produced by strong energy injection from the core shortly before collapse, and that circumstellar interaction is disfavored by the spectra and light curve.

What carries the argument

The load-bearing object is the analytic scaling relation for hydrogen-recombination plateau supernovae in the form used by Popov (1993) and Kasen & Woosley (2009): $L_{\rm SN} \propto E_k^{5/6} M_{\rm ej}^{-1/2} R_0^{2/3} \kappa^{-1/3} T_I^{4/3}$, $t_{\rm SN} \propto E_k^{-1/6} M_{\rm ej}^{1/2} R_0^{1/6} \kappa^{1/6} T_I^{-2/3}$, with $v_{\rm SN} \approx (2E_k/M_{\rm ej})^{1/2}$. These connect the three observed quantities---plateau luminosity, plateau duration, and ejecta velocity---to the three unknown explosion parameters. The paper assumes the opacity $\kappa$ and ionization temperature $T_I$ are universal among Type IIP SNe, then uses SN 2009kf, whose radiation-hydrodynamic model gives $E_k = 2.8$ foe (units of $10^{51}$ erg), $M_{\rm ej} = 11\,M_\odot$, and $R_0 \approx 6000\,R_\odot$, together with four other reference SNe, to solve for SN 2023gfo's parameters; the radius is the parameter that comes out anomalously large.

Extended reading notes

Core claim

On the paper's own terms, SN 2023gfo is a Type IIP supernova that is overluminous for its plateau duration: the light curve looks normal in shape and length, yet the corrected luminosity is exceptionally high. The paper derives extinction $A_V = 2.1$ mag from matching the observed $V-JHK_s$ color evolution to templates of normal Type IIP SNe, checks it against the Balmer decrement, and then measures a peak bolometric luminosity reached near day 24. Feeding the plateau luminosity, plateau duration, and expansion velocity into the analytic scaling relations of Popov and Kasen & Woosley---anchored by SN 2009kf and four well-studied Type IIP SNe---gives explosion energy $E_k \approx 1.9 \pm 0.9 \times 10^{51}$ erg, ejecta mass $M_{\rm ej} \approx 13 \pm 4.5\,M_\odot$, and progenitor radius $R_0 \approx 3{,}300 \pm 500\,R_\odot$. Because the inferred radius is consistently large regardless of which reference object is used, the paper treats the inflated progenitor as a robust inference and connects it to pre-explosion envelope inflation rather than to ejecta-CSM interaction, for which it finds no observational support.

Load-bearing premise

The load-bearing premise is that SN 2023gfo's intrinsic colors are exactly those of normal Type IIP supernovae, so the entire extinction correction is set by template matching; if the supernova is intrinsically redder because its photosphere is cooler and more extended, $A_V = 2.1$ mag is too high and the inferred luminosity and radius are overestimated.

Editorial extensions

If this is right

  • SN 2023gfo becomes a second independent example, after SN 2009kf, of a Type IIP supernova with high luminosity, high expansion velocity, and a normal plateau but an inferred pre-supernova radius near or above $3000\,R_\odot$.
  • If the radius inference holds, explosion energy and ejecta mass are close to normal, so the luminosity excess is an envelope-geometry effect rather than an energy-scale effect.
  • The absence of flash-ionized emission lines and of bumps or rapid rises in the early light curve indicates that a dense confined circumstellar shell is not powering the event; any final-stage mass loss must be weak or optically thin.
  • Pre-explosion energy injection large enough to expand the envelope by this factor becomes an observationally motivated channel, giving final-burning wave-transport models a concrete event to reproduce.
  • The same measurement strategy applied to future overluminous Type IIP events at earlier phases can separate inflation from interaction by looking for the shock-cooling signature and blue flash features.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the inflated-envelope picture is right, the photosphere should have been unusually large and cool in the first days after shock breakout; SN 2023gfo's earliest spectrum (day 4) and first regular photometry (day 6) may have only partly sampled that epoch, so very early observations of similar events could test this directly.
  • The template-matching extinction and the radius inference push in the same direction: intrinsic redness that mimics dust both lowers the corrected luminosity and shrinks $R_0$, so an independent host-galaxy reddening measurement would settle how extreme the event really is.
  • A population of such events would bias luminosity-based distance methods for Type IIP SNe at the bright end, because the scaling relations tie luminosity to radius; the bias could be calibrated by comparing radii inferred this way with radii from progenitor imaging.
  • Inverting the same scaling relations for a larger photometric sample would turn the single-object radius estimate into a distribution, testable against stellar-evolution models of late-stage envelope inflation.
Original abstract

We present near-infrared (NIR) and optical observations of the highly reddened Type IIP supernova (SN) 2023gfo in the nearby galaxy NGC 4995 ($d = 26.4 \pm 3.2$ Mpc), which reached a high peak luminosity of $M_V = -18.6$ mag. The SN was initially detected as a faint red event, with $B-V = 0.8$ mag at the beginning of the plateau phase. By comparison with template, we estimate a total extinction of $A_V = 2.1$ mag. After correcting for this extinction, we derive a peak quasi-bolometric luminosity of $(5.9 \pm 1.5)\times10^{42}$ erg s$^{-1}$, placing this event among the most luminous SNe IIP, while its plateau duration remains within the normal range. The early-phase optical spectrum exhibits a P-Cygni profile of H$\alpha$, with a broad absorption of $V$ = $13{,}800$ km s$^{-1}$, which is among the highest observed for SNe IIP at comparable epochs. The high luminosity and the normal plateau duration suggest that this event represents an outlier. Applying an analytical model, we infer an unusually large progenitor radius. This may indicate that the progenitor experienced an extreme energy injection from the core to the envelope shortly before explosion, resulting in a substantially inflated radius. While ejecta-circumstellar matter (CSM) interaction could in principle account for the high luminosity, we find no observational evidence supporting strong interaction.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 7,198 input tokens.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.56 · human participants 0.01 · controlled comparison 0.19 · randomized assignment 0.01 · states quantitative result 0.99 · compares with prior results 0.89 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

We present near-infrared (NIR) and optical observations of the highly reddened Type IIP supernova (SN) 2023gfo in the nearby galaxy NGC 4995 ($d = 26.4 \pm 3.2$ Mpc), which reached a high peak luminosity of $M_V = -18.6$ mag. The SN was initially detected as a faint red event, with $B-V = 0.8$ mag at the beginning of the plateau phase. By comparison with template, we estimate a total extinction of $A_V = 2.1$ mag. After correcting for this extinction, we derive a peak quasi-bolometric luminosity of $(5.9 \pm 1.5)\times10^{42}$ erg s$^{-1}$, placing this event among the most luminous SNe IIP, while its plateau duration remains within the normal range. The early-phase optical spectrum exhibits a P-Cygni profile of H$\alpha$, with a broad absorption of $V$ = $13{,}800$ km s$^{-1}$, which is among the highest observed for SNe IIP at comparable epochs. The high luminosity and the normal plateau duration suggest that this event represents an outlier. Applying an analytical model, we infer an unusually large progenitor radius. This may indicate that the progenitor experienced an extreme energy injection from the core to the envelope shortly before explosion, resulting in a substantially inflated radius. While ejecta-circumstellar matter (CSM) interaction could in principle account for the high luminosity, we find no observational evidence supporting strong interaction.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We present near-infrared (NIR) and optical observations of the highly reddened Type IIP supernova (SN) 2023gfo in the nearby galaxy NGC 4995 ($d = 26.4 \pm 3.2$ Mpc), which reached a high peak luminosity of $M_V = -18.6$ mag. contribution 0.96 0.96 0.09 asserted 1.00
s1 The SN was initially detected as a faint red event, with $B-V = 0.8$ mag at the beginning of the plateau phase. result 1.00 0.84 0.02 asserted 1.00
s2 By comparison with template, we estimate a total extinction of $A_V = 2.1$ mag. result 0.71 0.89 0.03 asserted 0.95
s3 After correcting for this extinction, we derive a peak quasi-bolometric luminosity of $(5.9 \pm 1.5)\times10^{42}$ erg s$^{-1}$, placing this event among the most luminous SNe IIP, while its plateau duration remains within the normal range. result 0.99 0.96 0.41 asserted 1.00
s4 The early-phase optical spectrum exhibits a P-Cygni profile of H$\alpha$, with a broad absorption of $V$ = $13{,}800$ km s$^{-1}$, which is among the highest observed for SNe IIP at comparable epochs. result 1.00 0.92 0.05 asserted 1.00
s5 The high luminosity and the normal plateau duration suggest that this event represents an outlier. interpretation 0.98 0.62 0.50 hedged possibility 0.92
s6 Applying an analytical model, we infer an unusually large progenitor radius. result 0.76 0.95 0.21 asserted 0.92
s7 This may indicate that the progenitor experienced an extreme energy injection from the core to the envelope shortly before explosion, resulting in a substantially inflated radius. interpretation 1.00 0.32 0.28 hedged possibility 0.99
s8 While ejecta-circumstellar matter (CSM) interaction could in principle account for the high luminosity, we find no observational evidence supporting strong interaction. result 0.67 0.92 0.08 asserted 0.69

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from observation or experiment 0.99.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. The optical and NIR light curve of SN 2023gfo. Photometric data are color-coded and plotted with various symbols: ATLAS c and o bands (squares), GIT g, r, i, and z bands (triangles), HOWPol B, V, R, and I bands (diamonds), and kSIRIUS J, H, and Ks bands (circles). The B, V , R, I, J, H, and Ks-band magnitudes are in the Vega system, and c, o, g, r, i, and z-band ones in the AB system. Each magnitude is artificially shifted to distinguish the light curves. Recently, highly-ionized emission lines with a blue continuum were detected for some Type IIP SNe during their early phases…
Figure 2. The ATLAS c-band and HOWPol V -band light curve of SN 2023gfo compared with the V -band ones of Type IIP SNe in the CSP sample (Anderson et al. 2014), normalized to the peak magnitude (set to zero). 2. OBSERVATIONS AND DATA REDUCTION SN 2023gfo was discovered at 16.2 magnitude by the Asteroid Terrestrial Impact Last Alert System (ATLAS; Tonry et al. 2018; Smith et al. 2020) on 20 April 2023 (UT) (MJD 60054.2) (Tonry et al. 2023). Prior to discovery, this object was detected at 19.2 mag on MJD 60051.2, while the last non-detection was reported at MJD 60050.0 with a limiting magnitude…
Figure 3. The V -JHKs color evolution of SN 2023gfo compared with those of other SNe 2003hn (Krisciunas et al. 2009), 2008in (Roy et al. 2011), 2012A (Tomasella et al. 2013), 2012ec (Barbarino et al. 2015), and 2013ej (Huang et al. 2015). Blue points represent SN 2023gfo before the extinction correction, while red points show the extinction-corrected SN 2023gfo with AV = 2.1 mag. The green-color solid line is represents a linear function fitting to combined data of comparative SNe. standard IRAF tasks such as DAOPHOT (Stetson 1987). For the optical observations, the photometric calibration…
Figure 4. The J (left top), H (right top), Ks (left bottom), and V band (right bottom) absolute magnitude light curves of SN 2023gfo. The J and Ks band light curves are compared with those of SNe 1999em (Elmhamdi et al. 2003), 2003hn (Krisciunas et al. 2009), 2004et (Maguire et al. 2010), 2005cs (Pastorello et al. 2009), 2008in (Roy et al. 2011), 2012A (Tomasella et al. 2013), 2012ec (Barbarino et al. 2015), 2013ej (Huang et al. 2015), and 2023ixf (Yamanaka et al. 2023; Singh et al. 2024). For the V and H-band, the samples from (Martinez et al. 2022) are shown for comparison. The red points…
Figure 5. Top: Distribution of the plateau length, as defined by Anderson et al. (2014), for the CSP Type II SN sample. The positions of SN 2023gfo and SN 2009kf are indicated in red and blue, respectively. Bot￾tom: Distribution of the peak absolute magnitudes in the V band for the same sample, with SN 2023gfo and SN 2009kf highlighted. 40.5 41 41.5 42 42.5 43 0 50 100 150 logLbol (erg s-1 ) Days from the explosion 23gfo 99em 03hn 05cs 08in 12A 13ej
Figure 6. The bolometric light curve of SN 2023gfo compared with those of SNe 1999em (Elmhamdi et al. 2003), 2003hn (Krisciunas et al. 2009), 2005cs (Pastorello et al. 2009), 2008in (Roy et al. 2011), 2012A (Tomasella et al. 2013), and 2013ej (Huang et al. 2015). The red point represents SN 2023gfo. The horizontal axis shows days since explosion, and the vertical axis shows the logarithm of the bolometric luminosity
Figure 7. (Left) Optical spectra of SN 2023gfo obtained at t = 4 d, 5 d, and 11 d, displayed from top to bottom, respectively. The flux has been corrected for the total line-of-sight extinction, dominated by the host-galaxy component, using AV = 2.1 mag. The spectra are shown in the rest frame of the host galaxy, determined from the narrow host-galaxy emission lines. (Right) Optical spectrum of SN 2023gfo at t = 11 d, compared with spectra of Type IIP SNe 2007od (Inserra et al. 2011), 2004et (Sahu et al. 2006), and 2013ej (Valenti et al. 2014) as similar phases. absorption features of a…

Figures reproduced from arXiv:2608.16006 by the authors.

References
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Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

What it cites · 15 sentences without a confident label

Uses the method or tool of 3 papers
Uses data or values from 4 papers
Compares with 2 papers
Cites as background 1 paper
  • Massive stars [ref] reach the end of their evolutionary stage and subsequently undergo core-collapse supernovae (CCSNe), i.e., terminal explosions of massive stars.

    How Massive Single Stars End their Life · Introduction · 1.00

Discussion

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