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LOFAR non-detections of SN 2023ixf in its first year post-explosion

T0 review · 0 major / 5 minor · reviewed 2026-08-11 · deepseek-v4-flash

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Pith's one-line read The paper reports that a year of LOFAR monitoring at 144 MHz found no radio emission from SN 2023ixf, down to about 80 microjansky at 3σ, consistent with higher-frequency light curves.

desk verdict A clean, honest null result from 14 LOFAR epochs; non-detections match higher-frequency data, and the paper doesn't overclaim. read the letter →

arxiv 2412.14275 v1 pith:QNE6XWNV submitted 2024-12-18 astro-ph.HE

R. Timmerman , M. Arias , A. Botteon This is my paper · ORCID
classification astro-ph.HE
keywords supernovaecore-collapseSN2023ixfLOFARlow-frequencyradioemissionnon-detectioncircumstellarmediumfree-freeabsorption
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 2023ixf is the nearest core-collapse supernova since SN 2014J, and this paper reports the most sustained low-frequency radio watch of it yet: 14 LOFAR observations at 144 MHz spanning 8 to 368 days after explosion. None of them detected the supernova, with a 3σ sensitivity of about 80 μJy. The null result is consistent with published VLA, GMRT, and NOEMA detections at higher frequencies, where the supernova is bright and rising slowly. The authors are explicit that these data cannot yet constrain the free-free absorption from the dense circumstellar medium; they set a baseline that LOFAR 2.0, expected to start science operations in early 2026, should be able to break.

What carries the argument

The machinery is the time-resolved 3σ upper-limit comparison: each of the 14 LOFAR epochs is calibrated with the Prefactor pipeline, imaged with WSClean, and the noise at the supernova position is converted into a flux-density upper limit overlaid on the higher-frequency light curve. The physical mechanism the campaign was designed to probe is free-free absorption by the dense circumstellar medium of the progenitor, which suppresses low-frequency radio emission early in the explosion's evolution.

What would settle it

Re-reduce the 14 epochs with an independent calibration and imaging pipeline and inspect the supernova position in each epoch: a source appearing above the local 3σ noise in any epoch would falsify that epoch's non-detection, while a deep stack that still shows nothing at the position would confirm the result at better sensitivity.

Watch

Extended reading notes

Core claim

The paper establishes that SN 2023ixf was not detected in any of the 14 LOFAR epochs at 144 MHz, with a per-epoch 3σ sensitivity of approximately 80 μJy. These non-detections are consistent with the higher-frequency radio light curve, which rises slowly and is modulated by free-free absorption from a dense circumstellar medium. At the achieved sensitivity, the predicted 150 MHz synchrotron flux on day 400 is only about 14 μJy, well below the detection threshold, so the data cannot constrain the absorption parameters. The paper looks ahead to LOFAR 2.0, when the predicted flux at these frequencies should reach roughly 200 μJy and become detectable.

Load-bearing premise

The result rests on the LOFAR data being calibrated and imaged well enough that a genuine radio source at the supernova's position would have shown up above the quoted ~80 μJy 3σ noise level.

Editorial extensions

If this is right

  • SN 2023ixf remained undetected at 144 MHz in every LOFAR epoch between 8 and 368 days after explosion, with 3σ upper limits around 80 μJy.
  • The LOFAR non-detections are consistent with the VLA, GMRT, and NOEMA detections at higher frequencies, so no low-frequency excess is required by the data.
  • The observations cannot constrain the free-free absorption from the circumstellar medium, because the predicted 150 MHz flux on day 400 (~14 μJy) is below the detection threshold.
  • If the broken-power-law model is correct, LOFAR 2.0 should detect the supernova at roughly 200 μJy when science operations begin in early 2026.
  • For future nearby radio supernovae, a slower monitoring cadence with intervals of months would be a more effective strategy than dense early observations, given how slowly SN 2023ixf brightened.

Reading between the lines

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

  • The authors do not say this, but stacking the 14 epochs in the uv-plane would improve sensitivity by roughly a factor of four and could push the limit below 30 μJy, enough to test the day-400 model prediction before LOFAR 2.0 comes online.
  • A reader might take the non-detection as evidence for free-free absorption, but the paper's model comparison shows the synchrotron-only prediction is already below the LOFAR threshold; the non-detection therefore does not discriminate between absorbed and unabsorbed models.
  • The paper's final suggestion that future monitoring should use a slower initial cadence could be turned into a concrete rule: for Type IIP supernovae with slow radio rises, schedule the first low-frequency observation a few months after explosion rather than immediately.
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Editorial analysis

A structured set of objections, weighed in public.

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

Referee Report

0 major / 5 minor

Summary. The manuscript reports a LOFAR 144 MHz monitoring campaign of the Type IIP supernova SN 2023ixf in M101, consisting of 14 epochs between 26 May 2023 and late May 2024 (about 8–368 days after explosion). Using the international LOFAR array, calibrated with Prefactor and imaged with WSClean, the authors find no significant point-source emission at the supernova position in any epoch. They quote a sensitivity of roughly 80 μJy (3σ), plot the epoch-by-epoch upper limits against published higher-frequency detections from Nayana et al. (2024) and other works, and conclude that the non-detections are consistent with the slow, absorbed radio rise inferred at higher frequencies. The authors explicitly state that the data cannot currently constrain the circumstellar-medium free-free absorption, and they predict that LOFAR 2.0 will detect the source around 2026.

Significance. This is a useful and well-scoped null result: systematic low-frequency (<200 MHz) monitoring of a nearby core-collapse supernova in its first year is rare, and the 14-epoch LOFAR upper limits provide an observational constraint that future modeling of SN 2023ixf and similar events can use. The paper's strengths are its conservative language, the explicit acknowledgment that the LOFAR data do not constrain the absorbing CSM, and the reliance on external published light-curve fits for the comparison, which keeps the argument free of circularity. The analysis is not fully reproducible from the manuscript alone, because per-epoch noise levels and imaging parameters are not tabulated.

minor comments (5)
  1. [Observations & Calibration; Figure 1] The quantitative claim of '~80 μJy sensitivity' at 144 MHz is not supported by a reproducible measurement in the text: no per-epoch image rms, synthesized beam size, or 3σ upper limit at the SN position is reported, and Figure 1 only shows the limits graphically. Please add a table listing epoch date, days post-explosion, on-source time, synthesized beam, local rms, and the corresponding 3σ point-source upper limit; this is the core data product of a non-detection paper.
  2. [Abstract; Results & Discussion] Please define whether '~80 μJy' refers to the median, best, or typical 3σ limit across the 14 epochs, since the per-epoch limits appear to vary in Figure 1 and the abstract's summary statistic is otherwise ambiguous.
  3. [Observations & Calibration] Please state explicitly how the 3σ sensitivity at the supernova position was measured (e.g., local image rms converted to a point-source limit using the synthesized beam) and whether the SN is unresolved in these images, since the entire non-detection argument assumes a point source.
  4. [Results & Discussion] The final statement that LOFAR 2.0 will detect the source at 'approximately ~200 μJy' should specify the assumed epoch (e.g., early 2026, roughly 950 days post-explosion) and quote the extrapolated flux from the cited Nayana et al. fitted power laws, rather than presenting the number without a derivation.
  5. [Throughout; References] Please correct minor typographical issues: 'Giant Meterwave Radio Telescope' should be 'Giant Metrewave Radio Telescope', the telescope name should be consistently written as 'LOFAR' rather than alternating with 'LOF AR', and the abstract's phrase 'At the time, we are not able to constrain...' is awkward and should be rephrased.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the non-detection claim is a direct observational result with no fitted input or self-citation chain load-bearing on the conclusion.

full rationale

The paper's central claim is a direct observational measurement: 14 LOFAR epochs between 8 and 368 days post-explosion show no point-source emission at the position of SN 2023ixf above the local 3σ noise level (~80 μJy at 144 MHz). This claim does not depend on any parameter fitted within the paper. The calibration uses Prefactor and WSClean, and the phrase 'we adopted the same calibration strategy for the International LOFAR Telescope as used in Timmerman et al. (2022)' is a data-processing recipe, not a load-bearing scientific premise that imports the non-detection result. The comparison data at higher frequencies come from external publications (Nayana et al. 2024; Iwata et al. 2024; Matthews et al. 2023), and the day-400 150 MHz flux of ~14 μJy is explicitly taken from Nayana et al.'s published fitted functions, so no fitted input is renamed as a prediction here. The paper also explicitly refrains from overinterpreting the null result, stating it cannot constrain CSM properties. The weakest assumption—that the local rms and flux scale accurately represent a point-source upper limit—is a standard observational assumption, not a circular one. No equation or definition reduces the conclusion to an input, and no self-citation is invoked to forbid alternatives or force the interpretation. The absence of a per-epoch rms table is a presentation limitation, not circularity. Therefore the derivation is self-contained for the claim it actually makes.

Assumptions & free parameters 0 free parameters · 2 assumptions · 0 invented entities

No free parameters are introduced by this paper; the only model parameters referenced (Nayana et al. 2024) are external published fits used for comparison, not for the central non-detection claim. The paper relies on standard reduction assumptions and on the source being a point source at the known location.

assumptions (2)
  • domain assumption Standard LOFAR calibration and imaging (Prefactor, WSClean) produce accurate flux densities and noise statistics.
    Used to convert visibility data into the images from which the non-detections are measured; located in Observations & Calibration.
  • domain assumption Radio emission from SN 2023ixf would appear as a point source at the LOFAR resolution and at the cataloged position.
    The upper limit is derived by searching for emission at the known SN position; if the source were extended or positionally offset, the limit could be misleading.

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Cite this review

Pith. "Pith review of LOFAR non-detections of SN 2023ixf in its first year post-explosion." pith.science (2026). https://pith.science/paper/QNE6XWNV

@misc{pith2026241214275,
  author       = {Pith},
  title        = {Pith review of: LOFAR non-detections of SN 2023ixf in its first year post-explosion},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/QNE6XWNV}},
  note         = {Machine review of arXiv:2412.14275}
}
read the original abstract

We used the LOFAR telescope to monitor SN 2023ixf, a core-collapse supernova in M101, between 8 and 368 days post-explosion. We report non-detections down to ~80 {\mu}Jy sensitivity at 144 MHz. Our non-detections are consistent with published radio observations at higher frequencies. At the time, we are not able to constrain the properties of low-frequency absorption due to the progenitor star's circumstellar medium via these LOFAR observations.

Figures

Figures reproduced from arXiv: 2412.14275 by the authors.

Figure 1
Figure 1. Radio continuum detections of SN 2023ixf obtained at higher frequencies combined with the non-detections obtained from LOFAR observations indicated at the 3σ noise level. RESULTS & DISCUSSION We searched the final images for radio emission in the direction of SN 2023ixf but were unable to detect significant emission in any of our epochs. Our non-detections are plotted in [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. SN 2023ixf: The Closest Supernova of the Decade

    astro-ph.HE 2025-07 unverdicted novelty 1.0 of 10

    SN 2023ixf is a type II supernova that exploded inside dense, confined circumstellar material lost by its red supergiant progenitor in the final years before explosion, as established by synthesizing over 80 published...

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