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arxiv: 2605.10427 · v1 · submitted 2026-05-11 · 🌌 astro-ph.EP

Recognition: no theorem link

Comparing Results from Two Uniform Phase Curve Surveys

Emeline Decocq , Mark Swain , Lisa Dang , David R. Ciardi , Geoffrey Bryden
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Pith reviewed 2026-05-12 05:21 UTC · model grok-4.3

classification 🌌 astro-ph.EP
keywords exoplanet phase curvesSpitzer observationsdata analysis comparisonKepler's third lawsystem parametersNASA Exoplanet Archivehot Jupiters
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The pith

Two Spitzer phase curve studies produce similar population results but differ for individual planets and highlight parameter inconsistencies with Kepler's third law.

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

This paper compares the two most recent comprehensive Spitzer 4.5 micron phase curve surveys by Dang et al. and Swain et al. The studies use different methods to correct for instrument systematics and select system parameters. At the population level the results for radius ratio, eclipse depth, phase amplitude and offset are similar. For individual planets the phase curve offsets often differ, which may stem from either the reduction methods or the chosen parameters. The authors also check consistency with Kepler's third law and find at least one case of inconsistency from the same source, leading to the recommendation that such checks are worthwhile for archival parameters.

Core claim

The two studies produce similar results at the population level although results for individual planets can vary, especially for phase curve offset values. Examination of the differences suggests they could arise from data reduction methods or system parameter choices. One case was identified where stellar mass, planet semi-major axis, and orbital period from the same publication did not satisfy Kepler's third law. Detailed analysis of archival system parameters indicates that testing reported or selected parameters for consistency with Kepler's third law is worthwhile.

What carries the argument

Comparison of exoplanet parameters including planet-to-star radius ratio, eclipse depth, phase curve amplitude and offset, together with verification of input parameters against Kepler's third law.

If this is right

  • The two independent analyses agree on average properties across the sample of planets.
  • Phase curve offsets for specific planets are more sensitive to analysis choices than other measured quantities.
  • Some published system parameters may not be internally consistent with basic orbital mechanics.
  • Routine application of Kepler's third law checks can help catch errors in exoplanet databases.

Where Pith is reading between the lines

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

  • If parameter inconsistencies are common, they could introduce systematic biases in derived planetary properties across multiple studies.
  • Standardizing the system parameters used in phase curve modeling might reduce discrepancies between different analyses of the same data.
  • Meta-analyses of exoplanet atmospheres could benefit from filtering or correcting for such orbital parameter mismatches.

Load-bearing premise

That inconsistencies like the one found between stellar mass, semi-major axis and orbital period are common enough in the NASA Exoplanet Archive to make routine consistency testing worthwhile rather than being isolated cases.

What would settle it

Performing a systematic recalculation of orbital periods for all entries in the NASA Exoplanet Archive using Kepler's third law and determining the fraction that deviate from the reported periods by more than a small threshold.

Figures

Figures reproduced from arXiv: 2605.10427 by David R. Ciardi, Emeline Decocq, Geoffrey Bryden, Lisa Dang, Mark Swain.

Figure 1
Figure 1. Figure 1: A comparison of the most important phase curve parameters reported in the studies compared. Starting at the upper right and proceeding clockwise the panels compare the parameters: Rp/R⋆, Deptheclipse (in ppm), A (in ppm), and ϕ (in degree East). We have overlaid the unity line along with, two linear fits, Orthogonal Distance Regression (ODR) and Least Squares regression (Ordinary Least Square). could be du… view at source ↗
Figure 2
Figure 2. Figure 2: A comparison of the consistency score for Rp/R⋆, Deptheclipse, A, and ϕ using the equation 7 highlights that Rp/R⋆ and Deptheclipse are mostly consistent, whereas the phase curve offset shows the least consistency. The corre￾sponding results are reported in [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 4
Figure 4. Figure 4: A comparison is made between the equilibrium temperature calculated, using the equation 8 for both S25 and D25, and the equilibrium temperature given in the pa￾pers. In orange the data are from D25 and in black they are from S25. lar and orbital parameters, this demonstrates that the selection of system parameter is not the source of dis￾crepancy. So, to further investigate the likely origin of the differ￾… view at source ↗
Figure 5
Figure 5. Figure 5: Keplerian Consistency Score (equation 6) be￾tween the data from S25 and D25 with all the planets. We have overlaid unity as a dashed line. Looking at [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 7
Figure 7. Figure 7: Comparison between the period computed from the equation 3 and the period given in the Exoplanet Archive (for all data in grey and the default parameters in black). The five outliers highlighted with red circles are discussed in detail below. We can see that for the NEA “default parameters”, even if most of the points tend to align along the unity slope, for a period between 2 and 2.5 days, we have 5 out￾l… view at source ↗
Figure 6
Figure 6. Figure 6: WASP-33 b parameters from EXCALIBUR pipeline for the Run ID 698. We can see that all the system parameters are self￾consistent, as they all come from the same publication (A. Chakrabarty & S. Sengupta 2019). However, if we look at (A. Chakrabarty & S. Sengupta 2019) we can see that the physical parameters (such as planet ra￾dius, scale parameter and orbital separation) are ”ob￾tained and deduced from their… view at source ↗
read the original abstract

We present a comparison of the two most recent and comprehensive Spitzer phase curve studies - Dang et al. (2025) and Swain et al. (2025) - which report analyses of the Spitzer 4.5 $\mu$m phase curves. The studies employ different approaches for correcting instrument systematics and they also use different approaches for selecting the optimal exoplanet system parameters. To evaluate the level of consistency between the two studies, we compared the constraints on the ratio of planet-to-star radii ($R_P/R_\star$), eclipse depth ($F_P/F_\star$), phase curve amplitude ($A$), and phase curve offset ($\phi$). We find that the two studies produce similar results at the population level although results for individual planets can vary, especially for phase curve offset values. We examined the difference of planet system parameters to see if inconsistencies in individual planet results were due to data reduction methods or system parameter choices. We also examined whether the system parameters used by both studies were consistent with Kepler's third law. During this comparison, we identified one case where stellar mass, planet semi-major axis, and orbital period did not follow Kepler's law even though the values were all compiled from the same publication. To assess whether this kind of discrepancy was recurrent, we recalculated the orbital periods using Kepler's third law and compared them with the values listed in the NASA Exoplanet Archive. Our detailed analysis of archival system parameters strongly suggests that testing reported/selected parameters for consistency with Kepler's third law is worthwhile.

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.

Referee Report

2 major / 1 minor

Summary. The manuscript compares results from two independent Spitzer 4.5 μm phase curve surveys (Dang et al. 2025 and Swain et al. 2025) that differ in systematics correction and system parameter selection. It reports that the studies yield similar population-level constraints on Rp/R*, eclipse depth, phase curve amplitude, and offset, while individual planets (especially offsets) show more variation. The authors examine whether differences arise from data reduction or parameter choices and audit archival parameters for consistency with Kepler's third law, identifying one case of inconsistency among stellar mass, semi-major axis, and period from the same source. After recalculating periods via Kepler's law and comparing to the NASA Exoplanet Archive, they conclude that such consistency testing is worthwhile.

Significance. If the comparison and audit hold, the work provides a transparent, direct numerical assessment showing that population inferences from phase curves are robust to methodological differences, while flagging a concrete archival inconsistency that could motivate routine Kepler-law checks. The explicit recalculation step and focus on published values offer a reproducible example of how parameter vetting can be performed.

major comments (2)
  1. [Archival parameter consistency analysis] Abstract and the section on archival parameter consistency: The claim that the analysis 'strongly suggests that testing reported/selected parameters for consistency with Kepler's third law is worthwhile' rests on one identified inconsistency (stellar mass, semi-major axis, and orbital period from the same publication) plus an unspecified recalculation of periods compared to the NASA Exoplanet Archive. The manuscript provides no sample size for the archive check, no count or fraction of inconsistencies found, and no quantitative summary of differences, making it impossible to judge whether the single case is representative or to evaluate the strength of the suggestion.
  2. [Results on population and individual comparisons] The section describing the population-level comparison: The manuscript states that the two studies produce 'similar results at the population level' but does not report the number of planets in the comparison sample, the quantitative measures of agreement (e.g., mean differences, rms scatter, or correlation coefficients) for each of the four quantities, or the criteria used to define 'similar.' This information is required to substantiate the distinction drawn between population-level agreement and individual-planet variations, particularly for phase curve offsets.
minor comments (1)
  1. [Abstract and references] The abstract and main text refer to Dang et al. (2025) and Swain et al. (2025) without full bibliographic details; ensure the reference list contains complete citations including titles, journal, volume, and page information.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and detailed comments on our manuscript comparing the two Spitzer phase curve surveys. We address each major comment below and have revised the manuscript to provide the requested quantitative details and clarifications.

read point-by-point responses

  1. Referee: [Archival parameter consistency analysis] Abstract and the section on archival parameter consistency: The claim that the analysis 'strongly suggests that testing reported/selected parameters for consistency with Kepler's third law is worthwhile' rests on one identified inconsistency (stellar mass, semi-major axis, and orbital period from the same publication) plus an unspecified recalculation of periods compared to the NASA Exoplanet Archive. The manuscript provides no sample size for the archive check, no count or fraction of inconsistencies found, and no quantitative summary of differences, making it impossible to judge whether the single case is representative or to evaluate the strength of the suggestion.

    Authors: We appreciate the referee's observation that additional quantitative context would allow readers to better evaluate the archival consistency analysis. The Kepler's law check was performed on the system parameters for the planets analyzed in the two surveys, with periods recalculated and compared to the NASA Exoplanet Archive values. We acknowledge that the current manuscript does not report the sample size, the number of inconsistencies identified, or a summary of differences. In the revised version, we will explicitly state the number of planets checked, report the count and fraction of inconsistencies found (with the highlighted case being the clearest example from a single source), and include a quantitative summary of period differences (e.g., mean and maximum fractional discrepancies). These additions will support our suggestion that routine consistency testing is worthwhile while allowing readers to assess representativeness. We have updated the abstract and the relevant section accordingly. revision: yes

  2. Referee: [Results on population and individual comparisons] The section describing the population-level comparison: The manuscript states that the two studies produce 'similar results at the population level' but does not report the number of planets in the comparison sample, the quantitative measures of agreement (e.g., mean differences, rms scatter, or correlation coefficients) for each of the four quantities, or the criteria used to define 'similar.' This information is required to substantiate the distinction drawn between population-level agreement and individual-planet variations, particularly for phase curve offsets.

    Authors: We agree that quantitative metrics are necessary to rigorously support the distinction between population-level agreement and individual-planet variations. The comparison was performed on the planets common to both surveys. In the revised manuscript, we will report the exact number of planets in the comparison sample, provide quantitative measures of agreement including mean differences, RMS scatter, and correlation coefficients for Rp/R*, eclipse depth, phase curve amplitude, and offset, and clarify the criteria for 'similar' (ensemble-level consistency within reported uncertainties). These details will particularly highlight the greater scatter in offsets. We have revised the results section to include these statistics and supporting figures or tables. revision: yes

Circularity Check

0 steps flagged

No circularity in direct comparison and parameter audit

full rationale

The paper performs a descriptive population-level comparison of four reported quantities (Rp/R*, eclipse depth, amplitude, offset) between two published studies via direct numerical matching of their values, plus an explicit recalculation of orbital periods from Kepler's third law to audit one identified inconsistency in the NASA Exoplanet Archive. No mathematical derivations, fitted parameters, predictions, or ansatzes are introduced that could reduce to the paper's own inputs by construction. The central claims follow immediately from the described matching and standard-law recalculation steps without any self-referential closure.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The analysis rests on the assumption that published stellar and orbital parameters should satisfy Kepler's third law when drawn from the same source, plus the completeness and accuracy of the NASA Exoplanet Archive entries used for the broader check.

axioms (1)
  • standard math Kepler's third law (P² ∝ a³ / M_star) must hold for the compiled stellar mass, semi-major axis, and orbital period values.
    Invoked when the authors recalculated orbital periods and compared them to archive values to detect inconsistencies.

pith-pipeline@v0.9.0 · 5579 in / 1386 out tokens · 51701 ms · 2026-05-12T05:21:57.969456+00:00 · methodology

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Reference graph

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