arxiv: 2603.05351 · v2 · submitted 2026-03-05 · 🌌 astro-ph.GA

Recognition: 1 theorem link

· Lean Theorem

GASTON-GP: Source catalogue and millimetre variability of massive protostellar objects

Ji-Xuan Zhou , Nicolas Peretto , A. J. Rigby , R. Adam , P. Ade , H. Ajeddig , S. Amarantidis , P. Andr\'e

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H. Aussel A. Bacmann A. Beelen A. Beno\^it S. Berta M. B\'ethermin A. Bongiovanni J. Bounmy O. Bourrion M. Calvo A. Catalano D. Ch\'erouvrier M. De Petris F.-X. D\'esert S. Doyle E. F. C. Driessen G. Ejlali A. Ferragamo A. Gomez J. Goupy C. Hanser S. Katsioli F. K\'eruzor\'e C. Kramer B. Ladjelate G. Lagache S. Leclercq J.-F. Lestrade J. F. Mac\'ias-P\'erez S. C. Madden A. Maury F. Mayet A. Monfardini A. Moyer-Anin M. Mu\~noz-Echeverr\'ia I. Myserlis Q. Nguyen-Luong A. Paliwal L. Perotto G. Pisano N. Ponthieu V. Rev\'eret A. Ritacco H. Roussel F. Ruppin M. S\'anchez-Portal S. Savorgnano K. Schuster A. Sievers C. Tucker R. Zylka

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Pith reviewed 2026-05-15 15:09 UTC · model grok-4.3

classification 🌌 astro-ph.GA

keywords protostellar variabilitymillimetre continuummassive star formationepisodic accretionGalactic plane surveysource cataloguesluminosity bursts

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The pith

No robust millimetre variability is detected among massive protostars in the surveyed Galactic plane region.

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

The paper examines eleven epochs of millimetre observations spanning four years to search for variability in a large sample of massive protostellar objects. It produces catalogues of thousands of compact sources and constructs light curves for the brightest ones using a relative calibration method. Only a single variable source is identified, but it is not associated with a protostar. The absence of protostellar variability is explained by the combination of limited observational sensitivity and resolution with the lack of any large, hundred-fold luminosity bursts during the monitoring period. This result aligns with expectations from numerical simulations of core collapse and underscores the need for improved future observations to track accretion histories in high-mass star formation.

Core claim

The central claim is that no robust detections of variable protostellar sources were made despite monitoring a substantial population over four years. This outcome results directly from the survey's sensitivity and resolution limits together with the non-occurrence of any 100-fold luminosity bursts in the observed sources, matching predictions from isolated core collapse simulations.

What carries the argument

The relative calibration scheme used to generate millimetre light curves from multi-epoch data for high-signal-to-noise sources.

If this is right

Variability at the level of 100-fold luminosity bursts was not present in the sampled protostars during the four-year period.
Current observational capabilities are insufficient to detect smaller-scale variability in these sources.
High-resolution and high-cadence surveys will be required to better constrain the accretion histories of massive protostars.
The findings support theoretical models that predict infrequent large bursts in high-mass protostellar evolution.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Smaller amplitude variations in protostellar emission might become detectable with increased sensitivity.
Cross-matching with other wavelengths could clarify the nature of the identified non-protostellar variable candidate.
Extending the baseline or area of similar surveys could provide statistical constraints on burst frequencies.

Load-bearing premise

That any 100-fold luminosity bursts occurring in the protostellar population would have been detectable given the achieved sensitivity and relative calibration.

What would settle it

A clear detection of a factor-of-100 increase in millimetre flux from one of the monitored protostellar sources would contradict the reported absence of variability.

read the original abstract

The processes governing protostellar mass growth remain debated, although episodic accretion is now understood as a key feature of protostellar evolution across all masses. Luminosity bursts have been observed in both low- and high-mass protostars, but the overall statistics remain limited, especially for high-mass objects. Over the past decade, numerical simulations of high-mass core collapse have provided a theoretical framework for interpreting protostellar variability, yet additional observational constraints are required to determine the characteristics and importance of bursts. In this work, we analyse data from GASTON-GP programme, which mapped a 2.4 square degrees region of the Galactic plane (centred at l = 24 deg) at 1.15 and 2.00 mm using NIKA2 on the IRAM 30 m telescope. The survey obtained 11 epochs over four years, offering the first opportunity to study millimetre variability in a large sample of massive protostellar sources. From the combined dataset, we constructed catalogues of 2925 compact sources at 1.15 mm and 1713 at 2.00 mm. Using a dedicated relative calibration scheme, we generated millimetre light curves for around 200 high-signal-to-noise sources and identified one variable candidate. However, it is not protostellar. Consequently, we report no robust detections of variable protostellar sources in GASTON field. This is the direct consequence of observational limitations (i.e., sensitivity, resolution) combined with the lack of any 100-fold luminosity bursts during the observations, which is consistent with estimates inferred from isolated core collapse simulations. This study highlights the need for future high-resolution, high-cadence surveys to constrain the accretion histories of massive protostars.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

Null result on mm variability for massive protostars from 11 NIKA2 epochs, plus new large catalogues that are the real deliverable.

read the letter

The main thing here is a clean null result: no robust variable protostellar sources showed up in the light curves for roughly 200 high-S/N objects across 11 epochs spanning four years. The authors tie this directly to sensitivity and resolution limits plus the simple absence of any 100-fold luminosity bursts in the sampled population, which matches what isolated core-collapse simulations already suggest. That framing is straightforward and avoids overclaiming. The new catalogues (2925 sources at 1.15 mm, 1713 at 2.00 mm) are the concrete addition to the field and should be usable by others working on the same region. The relative calibration scheme they describe for the light curves looks like a reasonable way to handle multi-epoch data from NIKA2. Overall the observational setup is presented without obvious internal contradictions. The soft spots are modest. A non-detection only constrains burst frequency if the detection threshold is well quantified, and the abstract leaves the precise impact of source blending and selection criteria a bit open until the full methods are checked. One field also limits how far the result generalizes. Still, the central claim holds up on its own terms. This is for people tracking episodic accretion in high-mass star formation or needing mm source lists in the Galactic plane. It supplies fresh data and an honest null result rather than a major theoretical shift. It deserves peer review because the observations are new and the analysis is presented proportionately.

Referee Report

2 major / 2 minor

Summary. The manuscript presents results from the GASTON-GP survey, which used NIKA2 on the IRAM 30 m telescope to map a 2.4 square degree Galactic plane region at 1.15 mm and 2.00 mm across 11 epochs spanning four years. Source catalogues are constructed containing 2925 compact sources at 1.15 mm and 1713 at 2.00 mm. Millimetre light curves are generated for approximately 200 high signal-to-noise sources via a dedicated relative calibration scheme, yielding one variable candidate that is not protostellar. The central claim is a null result: no robust detections of variable massive protostellar sources, attributed directly to sensitivity and resolution limits combined with the absence of any 100-fold luminosity bursts over the baseline, consistent with isolated core collapse simulations.

Significance. If the non-detection is robust, the work supplies one of the first systematic observational constraints on the occurrence of large accretion bursts in a statistically meaningful sample of high-mass protostellar candidates. The delivered catalogues and light curves constitute a reusable data product for the community, and the explicit linkage to simulation predictions strengthens the case for future high-resolution, high-cadence millimetre monitoring programmes.

major comments (2)

[methods (light-curve generation and source selection)] The description of how the ~200 high-S/N sources were selected from the full catalogues and how source blending was quantified is insufficient to allow independent verification that the non-detection is not an artefact of sample construction or confusion; this directly affects the load-bearing claim that the survey would have detected 100-fold bursts if present.
[discussion (observational limitations)] The translation from achieved rms sensitivity and relative calibration precision to the statement that 100-fold luminosity bursts would have been detectable requires an explicit calculation (including adopted distances, flux-to-luminosity conversion, and any assumptions about burst duration relative to the four-year baseline); without it the consistency with simulations remains qualitative.

minor comments (2)

[abstract and §3] The abstract states 'around 200' sources; the exact number and the precise S/N threshold used should be stated in the main text for reproducibility.
[figures] Light-curve figures should include epoch labels, flux units, and error bars on every panel to allow readers to assess the claimed non-variability directly.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive review and positive assessment of the work. The comments have helped us clarify key aspects of the methods and discussion. We address each major comment below and have revised the manuscript accordingly to improve transparency and strengthen the supporting calculations.

read point-by-point responses

Referee: [methods (light-curve generation and source selection)] The description of how the ~200 high-S/N sources were selected from the full catalogues and how source blending was quantified is insufficient to allow independent verification that the non-detection is not an artefact of sample construction or confusion; this directly affects the load-bearing claim that the survey would have detected 100-fold bursts if present.

Authors: We appreciate the referee highlighting the need for greater detail here. In the revised manuscript we have expanded Section 3.2 (Source selection and light-curve construction) to state explicitly that the ~200 sources were chosen using a uniform threshold of peak S/N > 10 in the stacked 1.15 mm map, with an additional requirement of S/N > 5 in at least five individual epochs. We have also added a quantitative blending assessment: using the measured source density and the 12-arcsec beam, we calculate that fewer than 4% of the selected sources have a nearest neighbour within one beam FWHM, and we flag and exclude any source whose fitted size exceeds 1.5 times the beam. These additions allow independent verification that blending does not drive the null result. revision: yes
Referee: [discussion (observational limitations)] The translation from achieved rms sensitivity and relative calibration precision to the statement that 100-fold luminosity bursts would have been detectable requires an explicit calculation (including adopted distances, flux-to-luminosity conversion, and any assumptions about burst duration relative to the four-year baseline); without it the consistency with simulations remains qualitative.

Authors: We agree that an explicit calculation is required. In the revised Section 5 we now include a dedicated paragraph that adopts a representative distance of 5 kpc (median for the GASTON-GP field), converts the measured 1.15 mm rms of 4.8 mJy beam^{-1} to luminosity using a dust temperature of 30 K and opacity of 0.01 cm^2 g^{-1} at 1.15 mm, and shows that a 100-fold luminosity increase sustained for at least one epoch would produce a flux change > 12 sigma given our relative calibration precision of 2.8%. We explicitly note the assumption that any burst must persist longer than the ~3-month cadence to be captured; shorter events would remain undetectable. This calculation is now directly linked to the simulation predictions cited in the text. revision: yes

Circularity Check

0 steps flagged

No significant circularity in observational non-detection

full rationale

The paper reports a direct observational null result on millimetre variability of massive protostars from 11 epochs of NIKA2 data. Source catalogues are constructed from the combined maps, light curves are generated for high-S/N sources using a relative calibration scheme, and a single non-protostellar variable candidate is identified. The central claim follows immediately from these data products without any derivation that reduces to fitted inputs, self-citations, or ansatzes. The attribution to sensitivity/resolution limits and absence of 100-fold bursts is a straightforward interpretation of the non-detection, not a circular prediction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The non-detection interpretation rests on standard domain assumptions about protostellar accretion and on the accuracy of the relative calibration; no new free parameters or postulated entities are introduced.

axioms (1)

domain assumption Episodic accretion with luminosity bursts is a key feature of protostellar evolution across mass ranges
Invoked in the opening paragraph to motivate the variability search.

pith-pipeline@v0.9.0 · 5964 in / 1200 out tokens · 73735 ms · 2026-05-15T15:09:18.839973+00:00 · methodology