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REVIEW 2 major objections 5 minor 36 references

High-cadence microlensing surveys have found four cold giant planets orbiting low-mass stars beyond their snow lines.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

T0 review · grok-4.5

2026-07-11 16:42 UTC pith:EXZKHLCJ

load-bearing objection Four new cold giants from the standard high-cadence pipeline; careful modeling, prior-dependent masses, solid incremental addition to the homogeneous sample. the 2 major comments →

arxiv 2607.04594 v1 pith:EXZKHLCJ submitted 2026-07-06 astro-ph.EP

Four Cold Giant Planets Discovered by High-Cadence Microlensing Surveys

classification astro-ph.EP
keywords gravitational microlensingexoplanet detectioncold giant planetshigh-cadence surveysbinary-lens modelingangular Einstein radiusBayesian mass estimationsnow line
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

This paper reports four new giant planets found by watching short anomalies in high-cadence microlensing light curves from the KMTNet, OGLE, and PRIME surveys. Binary-lens models with mass ratios of order 10^{-3} fit the anomalies, and finite-source effects measured for three events yield the angular Einstein radius. A Bayesian analysis that folds in the event timescales and Einstein radii then converts those observables into physical parameters: hosts of roughly 0.07–0.6 solar masses, planets of 0.2–2.5 Jupiter masses, projected separations of 0.7–6 au (at or beyond the snow line), and distances of 6.6–7.9 kpc consistent with Galactic-bulge lenses. The detections enlarge the homogeneous sample of cold giants around low-mass stars that only microlensing can systematically reach, thereby tightening empirical constraints on how efficiently giant planets form beyond the snow line.

Core claim

Four microlensing events (OGLE-2016-BLG-0261, KMT-2025-BLG-0026, KMT-2025-BLG-0030, KMT-2025-BLG-2272) each show a short-duration anomaly that is well described by a binary-lens single-source model with planet-to-host mass ratio q ~ 10^{-3}. Secure finite-source measurements in three events give the angular Einstein radius; a Bayesian analysis of the measured timescales and Einstein radii then yields host masses ~0.07–0.6 M_⊙, companion masses ~0.2–2.5 M_J, projected separations ~0.7–6 au, and distances ~6.6–7.9 kpc, confirming that all four companions are cold giant planets orbiting low-mass hosts at or beyond the snow line and consistent with bulge lenses.

What carries the argument

Binary-lens single-source (2L1S) light-curve modeling that recovers the mass ratio q and normalized source radius ρ, followed by Bayesian conversion of the measured Einstein timescale t_E and angular Einstein radius θ_E = θ_*/ρ into host and planet masses and distances via a Galactic density–kinematics–mass-function prior.

Load-bearing premise

The adopted Galactic model for disk and bulge densities, kinematics, and the stellar mass function correctly supplies the prior probabilities that turn the measured event timescales and Einstein radii into host and planet masses.

What would settle it

High-resolution imaging years after the events that measures the lens flux and the lens–source relative proper motion; if those measurements force host masses or distances outside the reported Bayesian posteriors (or resolve the close–wide or inner–outer degeneracies in a way that contradicts the adopted solutions), the physical parameters claimed here would be ruled out.

Watch this falsifier. Get emailed when new claim-graph text bears on it.

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Editorial analysis

A structured set of objections, weighed in public.

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

Referee Report

2 major / 5 minor

Summary. The paper reports four cold giant planets discovered in high-cadence microlensing events OGLE-2016-BLG-0261, KMT-2025-BLG-0026, KMT-2025-BLG-0030, and KMT-2025-BLG-2272. Short-duration anomalies are modeled as 2L1S systems with mass ratios q ~ 10^{-3}. Finite-source effects yield angular Einstein radii for three events. Bayesian analysis using measured t_E and θ_E (with the Jung et al. 2021/2022 Galactic model and mass function) produces host masses ~0.07–0.6 M_⊙, companion masses ~0.2–2.5 M_J, projected separations ~0.7–6 au (at or beyond the snow line), and distances ~6.6–7.9 kpc consistent with bulge lenses. Degeneracies (inner–outer, close–wide, accidental) and 1L2S alternatives are quantified and discussed.

Significance. The work expands the homogeneous sample of cold giant planets from high-cadence surveys (KMTNet, OGLE, PRIME) and supplies additional empirical constraints on giant-planet occurrence around low-mass hosts beyond the snow line. The light-curve modeling is careful: grid searches, explicit treatment of known degeneracies, 1L2S tests where relevant, and secure ρ measurements for three of four events. Physical parameters rest on standard Bayesian conversion of independently measured (t_E, θ_E). The results are useful for demographic studies even if absolute masses shift modestly under prior variations, because the companions remain in the giant-planet regime for the reported q and s.

major comments (2)
  1. Section 5 and Table 6: For KMT-2025-BLG-0026 the close and wide solutions have substantially different q (4.62e-3 vs 0.50e-3) and ρ, yet only the close solution is used for the adopted θ_E and the primary physical-parameter summary. Although Δχ^{2} = 16.6 favors the close solution, the wide solution still yields a giant-planet mass (and a larger a_⊥). The paper should either present both posteriors side-by-side in the main text/table or quantify how the choice affects the claimed mass and separation ranges, so that the central claim does not rest solely on one branch of an accidental degeneracy.
  2. Section 5, Eqs. (3)–(5) and the weakest-assumption note: Absolute host and planet masses (and DL) depend on the Jung et al. (2021, 2022) Galactic density, kinematics, and mass-function prior. Reasonable variations of that prior can shift masses and distances by tens of percent. While the companions remain giant planets for the measured q, the paper should briefly test or cite the sensitivity of the reported medians and 1σ intervals to alternative standard priors (e.g., different disk/bulge mass functions or density profiles) so that the numerical ranges quoted in the abstract and Table 6 are not over-interpreted as prior-independent.
minor comments (5)
  1. Title page and abstract: Event naming is inconsistent (KMT-2016-BLG-1679 vs OGLE-2016-BLG-0261). Table 1 clarifies the correspondence, but the abstract and early text should use a single primary designation consistently.
  2. Table 3 and Table 4: HJD' zero-points differ between events (HJD-2450000 vs HJD-2460000). A single clarifying note in each table caption would prevent misreading of t0 values.
  3. Figure 5 and Section 4: For the two faint sources whose colors are taken from HST CMD alignment, a short quantitative statement of the color uncertainty (beyond the tabulated ± values) would strengthen the θ_* error budget.
  4. Section 3.2: The accidental (not classical close–wide) nature of the KMT-2025-BLG-0026 degeneracy is correctly identified; a one-sentence cross-reference to the analytic s† relation used for the other events would make the distinction even clearer.
  5. Scattered typographical issues (e.g., "Microle nsing", "F our", "OBSER V ATIONS", missing spaces in author lists) should be cleaned in production.

Circularity Check

0 steps flagged

No significant circularity: planet masses and distances are Bayesian posteriors from independently measured (tE, heta E) weighted by a previously published Galactic prior, not quantities forced by construction or by a self-referential fit.

full rationale

The derivation chain is linear and non-circular. Light-curve modeling (Sect. 3) yields free parameters (s, q, ho, tE, ਎tc.) by χ^{2} minimization against photometry; q ∼ 10^{-3} is read directly from the best-fit binary-lens solutions and is not defined in terms of the later mass posteriors. Angular Einstein radii (Sect. 4) follow from the standard relation heta E = heta*/ ho once source angular radii are calibrated against the red-clump centroid; these are independent photometric and color measurements. Physical parameters (Sect. 5, Eqs. 3–5) are obtained by Monte-Carlo weighting of a Galactic model (density, kinematics, mass function) with a Gaussian likelihood on the already-measured (tE, heta E). The model itself is taken from earlier published work (Jung et al. 2021, 2022) and is not re-fitted to the four events under study; the resulting host and planet masses are therefore ordinary Bayesian inferences, not tautological re-statements of fitted inputs. Degeneracies (inner–outer, close–wide, accidental) and 1L2S alternatives are explicitly tested and quantified by Δχ^{2}; none of them redefine the observables. Self-citations to the authors’ prior Galactic model are present but are not load-bearing in the circular sense: they supply a conventional prior whose assumptions are external to the present data set. No equation equates a claimed prediction to a free parameter of the paper, and no uniqueness theorem is imported to forbid alternatives. Score 1 reflects only the minor, non-circular self-citation of the prior; the central claim remains independently supported by the light-curve observables.

Axiom & Free-Parameter Ledger

3 free parameters · 4 axioms · 0 invented entities

The central mass and distance claims rest on measured light-curve parameters plus a published Galactic prior. Free parameters are the usual per-event lensing parameters fitted to photometry and the error-rescaling coefficients. Domain assumptions are the standard microlensing formalism and the adopted Galactic model/mass function. No new physical entities are postulated.

free parameters (3)
  • per-event (s, q, α, ρ, t0, u0, tE)
    Binary-lens parameters fitted to each light curve by χ² minimization; values listed in Tables 3–4.
  • error-bar rescaling (k, σ_min)
    Per-dataset coefficients chosen so that reduced χ² ≈ 1 (Table 2); standard but free.
  • source color–magnitude offsets relative to RGC
    Used to obtain de-reddened (V−I, I)0 and thence θ* via surface-brightness relations; measured but carry systematic uncertainty from RGC calibration.
axioms (4)
  • domain assumption Standard 2L1S microlensing magnification formalism (including finite-source effects) correctly describes the observed light curves.
    Invoked throughout Section 3; no alternative lens models beyond 1L2S tests are explored.
  • domain assumption Galactic model of Jung et al. (2021) for density and kinematics plus mass-function prescription of Jung et al. (2022) supply the correct prior for Bayesian mass inference.
    Explicitly adopted in Section 5; the posterior medians and disk/bulge fractions depend on this prior.
  • domain assumption Surface-brightness relations of Kervella et al. (2004) and color–color transformations of Bessell & Brett (1988) convert de-reddened photometry into angular source radius θ*.
    Used in Section 4 to obtain θE = θ*/ρ.
  • domain assumption RGC centroid provides an accurate reddening and distance reference for the source stars.
    Standard CMD calibration of Yoo et al. (2004) applied in Section 4.

pith-pipeline@v1.1.0-grok45 · 23253 in / 2684 out tokens · 19931 ms · 2026-07-11T16:42:46.696150+00:00 · methodology

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Cite this review

Pith. "Pith review of Four Cold Giant Planets Discovered by High-Cadence Microlensing Surveys." pith.science (2026). https://pith.science/paper/EXZKHLCJ

@misc{pith2026260704594,
  author       = {Pith},
  title        = {Pith review of: Four Cold Giant Planets Discovered by High-Cadence Microlensing Surveys},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/EXZKHLCJ}},
  note         = {Machine review of arXiv:2607.04594}
}
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read the original abstract

We report the discovery of four cold giant planets identified through the analysis of microlensing events detected by high-cadence surveys: OGLE-2016-BLG-0261, KMT-2025-BLG-0026, KMT-2025-BLG-0030, and KMT-2025-BLG-2272. The planetary signals appear as short-duration anomalies in the light curves and are well described by binary-lens single-source models with mass ratios between the lens components of order $q \sim 10^{-3}$. Finite-source effects are securely measured in three out of four events, enabling determinations of the angular Einstein radius. A Bayesian analysis incorporating the measured event timescale and angular Einstein radius yields host masses of $\sim 0.07$--$0.6~M_\odot$ and companion masses of $\sim 0.2$--$2.5~M_{\rm J}$, confirming that all companions lie in the giant-planet regime. The projected separations are ~ 0.7--6 au, placing all planets at or beyond the snow lines of their host stars. The inferred lens distances span $\sim 6.6$--$7.9$ kpc, with all systems consistent with bulge lenses. These detections expand the sample of cold giant planets from homogeneous high-cadence surveys and highlight the sensitivity of microlensing to planetary systems beyond the snow line, providing further constraints on the occurrence and properties of giant planets around low-mass stars.

Figures

Figures reproduced from arXiv: 2607.04594 by Andrew Gould, Andrzej Udalski, Byeong-Gon Park, Cheongho Han, Chihiro Ueda, Chung-Uk Lee, Daisuke Suzuki, David P. Bennett, Doeon Kim, Dong-Jin Kim, Dong-Joo Lee, Hibiki Yama, Hideaki Ose, Hongjing Yang, Ian A. Bond, Igor Soszy\'nski, In-Gu Shin, Jan Skowron, Jennifer C. Yee, Kansuke Nunota, Krzysztof A. Rybicki, Krzysztof Ulaczyk, Kyu-Ha Hwang, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mr\'oz, Michael D. Albrow, Micha{\l} K. Szyma\'nski, Motohide Tamura, Nicholas J. Rattenbury, Patryk Iwanek, Pawe{\l} Pietrukowicz, Przemek Mr\'oz, Rados{\l}aw Poleski, Richard W. Pogge, Ryo Ogawa, Ryunosuke Oishi, Ryusei Hamada, Sang-Mok Cha, Seiya Nakayama, Seung-Lee Kim, Shota Miyazaki, Shuma Makida, Sun-Ju Chung, Szymon Koz{\l}owski, Takahiro Sumi, Takuto Tamaoki, Tutumi Nagai, Weicheng Zang, Yongseok Lee, Yoon-Hyun Ryu, Yossi Shvartzvald, Youn Kil Jung, Yuki Hirao, Yuki K. Satoh.

Figure 1
Figure 1. Figure 1: Light curve of the microlensing event OGLE-2016-BLG-0261. The bottom panel shows the full light curve, while the top panel presents a zoomed-in view of the peak region. The two insets in the bottom panel illustrate the lens-system configurations for the inner and outer 2L1S solutions. The coordinate system is centered on the host star, and all lengths are scaled to the angular Einstein radius. In each inse… view at source ↗
Figure 2
Figure 2. Figure 2: Lensing light curve of KMT-2025-BLG-0026. The small box in the bottom panel marks the region of the anomaly. The two sets of insets in the bottom panel show the lens-system configurations of the close (upper inset) and wide (lower inset) solutions. For each solution, the left inset shows the source trajectory relative to the lens positions (marked by blue dots), and the right inset presents a zoomed-in vie… view at source ↗
Figure 3
Figure 3. Figure 3: Light curve of lensing event KMT-2025-BLG-0030. The notation and layout are the same as those in [PITH_FULL_IMAGE:figures/full_fig_p008_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Light curve of KMT-2025-BLG-2272. The figure follows the same format as [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Locations of the source stars relative to the centroids of the red giant clump (RGC) in the color–magnitude diagram (CMD) constructed from KMTC observations (gray dots). For events whose source colors are determined using the CMD from HST observations, the HST CMD (brown dots) is also shown. The two insets in the bottom panel of [PITH_FULL_IMAGE:figures/full_fig_p010_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Bayesian posterior distributions for the host masses of the planetary systems. In each panel, the solid vertical line represents the median value, and the two dotted vertical lines indicate the 1σ uncertainty range. The blue and red curves show the contributions from the disk and bulge lens populations, respectively, while the black curve represents the sum of the two populations. provided by the measured … view at source ↗
Figure 7
Figure 7. Figure 7: Bayesian posterior distributions for the distances to the planetary systems. The notation is the same as in [PITH_FULL_IMAGE:figures/full_fig_p012_7.png] view at source ↗

discussion (0)

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