Modeling of CoRoT and Spitzer lightcurves in NGC 2264 caused by an optically thick warp

Erick Nagel; Jerome Bouvier

arxiv: 1906.10110 · v1 · pith:EPPS4ST3new · submitted 2019-06-24 · 🌌 astro-ph.SR

Modeling of CoRoT and Spitzer lightcurves in NGC 2264 caused by an optically thick warp

Erick Nagel , Jerome Bouvier This is my paper

Pith reviewed 2026-05-25 16:44 UTC · model grok-4.3

classification 🌌 astro-ph.SR

keywords lightcurvesdisk warpstellar occultationNGC 2264CoRoTSpitzeryoung starsinfrared emission

0 comments

The pith

CoRoT and Spitzer lightcurves of four stars in NGC 2264 are reproduced by an optically thick warp causing stellar occultation plus asymmetric disk emission.

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

The paper analyzes simultaneously observed optical and infrared lightcurves for four young stars in the NGC 2264 region. These lightcurves show strong resemblance between the two wavelengths, indicating a shared physical cause. The authors model the infrared flux as arising from a warp that includes an optically thick wall and an asymmetric disk beyond it. Optical variations are produced mainly by partial occultation of the star by this same warp. The model accounts for the observed amplitudes in all four systems by varying only the relative disk-to-wall flux and the azimuthal structure of the disk.

Core claim

The magnitude amplitude of the CoRoT and Spitzer observations for Mon-660, Mon-811, Mon-1140 and Mon-1308 can be described with the emission coming from the system components. The difference between them is the value of the disk flux compared with the wall flux and the azimuthal variations of the former. This result points out the importance of the hydrodynamical interaction between the stellar magnetic field and the disk.

What carries the argument

Optically thick warp consisting of a wall that produces stellar occultation in optical light and an asymmetric disk that produces infrared emission, allowing one structure to fit both wavelength regimes simultaneously.

If this is right

Hydrodynamical interaction between the stellar magnetic field and the disk is required to sustain the warp geometry that fits the data.
The same warp configuration can be used for other young stars whose optical and infrared lightcurves closely resemble each other.
No extra variability sources are needed to match the observed amplitudes once the wall and disk fluxes are adjusted.

Where Pith is reading between the lines

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

Similar warp structures may dominate photometric behavior in other pre-main-sequence stars with comparable multi-band lightcurves.
Repeated observations could test whether the azimuthal disk variations remain stable over multiple rotation periods.
The model predicts that the infrared lightcurve shape should track the optical one with a fixed lag set by the wall and disk geometry.

Load-bearing premise

A single warp structure with an optically thick wall and asymmetric disk is sufficient to reproduce both lightcurves without additional components such as stellar spots, accretion hotspots, or multiple warps.

What would settle it

New simultaneous optical and infrared observations that show phase or amplitude relations between the two bands that cannot be matched by varying only the disk-to-wall flux ratio and the azimuthal disk variations.

Figures

Figures reproduced from arXiv: 1906.10110 by Erick Nagel, Jerome Bouvier.

**Figure 1.** Figure 1: Sketch of the system modeled. The inclined straight lines represent two lines of sight with the same inclination crossing different sections of the system. The left line contributes to emission of the wall and the right line contributes to emission of the disk. In this case, all the stellar surface is occulted. The aim of this work is to consistently reproduce the observed amplitude of the CoRoT magnitude… view at source ↗

**Figure 2.** Figure 2: The wall temperature (Twall in Kelvin) at the vertical wall as a function of height (z in stellar radius) for Mon-660, Mon-811 and Mon-1308 grain sizes. These values are required to get the wall temperature (Twall) but it mainly depends on the distance to the star, thus, the values taken do not significantly change the modeled wall emission. In [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗

**Figure 3.** Figure 3: Modeled optical and 4.5µm lightcurves for Mon-660 at i = 77◦ . The modeled CoRoT lightcurve is represented by filled circles, and the modeled Spitzer photometric magnitudes at 4.5µm is plotted as solid squares. For comparison the observed +1σ CoRoT (points) and the +1σ Spitzer 4.5µm (asterixs) lightcurves are presented. We use all the cycles presented in McGinnis et al. (2015) to calculate the observed cur… view at source ↗

**Figure 4.** Figure 4: Flux contributions in the optical and the IR for Mon-660 at i = 77◦ . The modeled CoRoT and 4.5µm fluxes coming from the star are represented as filled squares and filled circles, respectively. The 4.5µm fluxes coming from the wall and the disk are plotted with solid triangles and asterixs, respectively. The light asterixs represent the total modeled flux. For this object, the bending wave and/or material … view at source ↗

**Figure 5.** Figure 5: Modeled optical and IR lightcurves for Mon-811 at i = 77◦ . The symbols definitions are the same as in [PITH_FULL_IMAGE:figures/full_fig_p011_5.png] view at source ↗

**Figure 6.** Figure 6: Flux contributions in the optical and the IR for Mon-811 at i = 77◦ . The symbols definitions are the same as in [PITH_FULL_IMAGE:figures/full_fig_p011_6.png] view at source ↗

**Figure 7.** Figure 7: Modeled optical and IR lightcurves for Mon-1140. The symbols definitions are the same as in [PITH_FULL_IMAGE:figures/full_fig_p013_7.png] view at source ↗

**Figure 8.** Figure 8: Flux contributions in the optical and the IR for Mon-1140. The symbols definitions are the same as in [PITH_FULL_IMAGE:figures/full_fig_p013_8.png] view at source ↗

**Figure 9.** Figure 9: Modeled optical and IR lightcurves for Mon-1308 at i = 77◦ . The symbols definitions are the same as in [PITH_FULL_IMAGE:figures/full_fig_p014_9.png] view at source ↗

**Figure 10.** Figure 10: Flux contributions in the optical and the IR for Mon-1308 at i = 77◦ . The symbols definitions are the same as in [PITH_FULL_IMAGE:figures/full_fig_p014_10.png] view at source ↗

read the original abstract

Aims: We present an analysis of simultaneously observed CoRoT and Spitzer lightcurves for $4$ systems in the stellar forming region NGC 2264: Mon-660, Mon-811, Mon-1140 and Mon-1308. These objects share in common a high resemblance between the optical and infrared lightcurves, such that the mechanism responsible to produce them is the same. The aim of this paper is to explain both lightcurves simultaneously with only one mechanism. Methods: We have modeled the infrared emission as coming from a warp composed of an optically thick wall and an optically thick asymmetric disk beyond this location. We have modeled the optical emission mainly by partial stellar occultation by the warp. Results: The magnitude amplitude of the CoRoT and Spitzer observations for all the objects can be described with the emission coming from the system components. The difference between them is the value of the disk flux compared with the wall flux and the azimuthal variations of the former. This result points out the importance of the hydrodynamical interaction between the stellar magnetic field and the disk. Conclusions: CoRoT and Spitzer lightcurves for the stellar systems Mon-660, Mon-811, Mon-1140 and Mon-1308 can be simultaneously explained using the emission coming from an asymmetric disk and emission with stellar occultation by an optically thick wall.

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

This applies an existing warp model to four NGC 2264 stars with paired CoRoT/Spitzer data, but does not clearly demonstrate that one shared geometry reproduces both bands.

read the letter

The paper takes simultaneous optical and infrared lightcurves for Mon-660, Mon-811, Mon-1140 and Mon-1308 and shows that an optically thick warp (wall plus asymmetric disk) can be adjusted to match the amplitudes in both. The resemblance between the bands is the starting point, and the modeling treats optical variability as partial occultation while IR comes from thermal emission off the same components. That is a direct, reasonable step for these objects and ties into the usual picture of magnetic truncation and disk warping in young stars. The differences they report between the four targets are mainly in the disk-to-wall flux ratio and the strength of azimuthal asymmetry, which is consistent with object-to-object variation in disk structure. The work is an application rather than a new derivation, and the abstract does not claim otherwise. The data are simultaneous, which is a plus for ruling out time-variable effects. The main gap is whether the geometry itself is held fixed across wavelengths. The description emphasizes post-fit adjustments to flux ratios without stating that warp height, radial location, and azimuthal extent were required to be identical in a joint optimization; only radiative properties were allowed to differ. No fit statistics, residuals, or exclusion of alternatives appear in the summary, so it is hard to judge how unique the solution is. If the full text shows explicit shared-parameter fits with quantitative measures, that would tighten the result. This is for people already working on YSO variability and disk-star coupling. A specialist would get concrete examples of how the warp parameters shift from object to object, but the paper does not reorganize the topic. It is worth sending to peer review so the joint-fitting details and any alternative explanations can be checked directly.

Referee Report

3 major / 1 minor

Summary. The paper presents modeling of simultaneous CoRoT optical and Spitzer infrared lightcurves for four pre-main sequence stars in NGC 2264 (Mon-660, Mon-811, Mon-1140, Mon-1308). It claims that both lightcurves can be explained by a single mechanism: an optically thick warp consisting of a wall that occults the star in optical wavelengths and an asymmetric disk that emits in the infrared, with differences in disk-to-wall flux ratio and azimuthal variations accounting for object-to-object differences.

Significance. If the central claim holds with a shared geometric warp structure across wavelengths, the work would provide evidence that magnetic field-disk interactions can produce warps responsible for observed multi-band photometric variability in young stellar objects. The approach of using one structure for both bands is potentially significant for understanding disk dynamics, though the current presentation relies on qualitative descriptions rather than quantitative validation.

major comments (3)

[Abstract] Abstract: The assertion that 'the magnitude amplitude of the CoRoT and Spitzer observations for all the objects can be described with the emission coming from the system components' lacks supporting quantitative metrics such as reduced chi-squared values, RMS residuals, or parameter uncertainties from the fits.
[Methods/Results] Methods and Results sections: The modeling of optical and IR lightcurves is described separately ('We have modeled the infrared emission as coming from a warp...' and 'We have modeled the optical emission mainly by partial stellar occultation by the warp'), without explicit statement or demonstration that geometric parameters of the warp (height, azimuthal extent, location) are held fixed and shared between the two bands in a joint fit.
[Results] Results: The differences between objects are attributed to 'the value of the disk flux compared with the wall flux and the azimuthal variations of the former', but these are post-hoc fitted quantities; the manuscript does not show that the model makes a priori predictions independent of tuning to each lightcurve.

minor comments (1)

[Abstract] Abstract: The conclusion restates the aims without adding new quantitative insight; a brief summary of fit quality or parameter ranges would improve clarity.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive report. We respond point-by-point to the major comments below.

read point-by-point responses

Referee: [Abstract] Abstract: The assertion that 'the magnitude amplitude of the CoRoT and Spitzer observations for all the objects can be described with the emission coming from the system components' lacks supporting quantitative metrics such as reduced chi-squared values, RMS residuals, or parameter uncertainties from the fits.

Authors: The abstract summarizes the main result at a high level. The body of the manuscript presents the modeling, but we agree that explicit quantitative fit statistics were not reported. We will add reduced chi-squared values, RMS residuals, and parameter uncertainties to the Results section in the revised version. revision: yes
Referee: [Methods/Results] Methods and Results sections: The modeling of optical and IR lightcurves is described separately ('We have modeled the infrared emission as coming from a warp...' and 'We have modeled the optical emission mainly by partial stellar occultation by the warp'), without explicit statement or demonstration that geometric parameters of the warp (height, azimuthal extent, location) are held fixed and shared between the two bands in a joint fit.

Authors: The warp is a single physical structure whose geometric parameters are therefore shared by construction between the optical and infrared models. The separate wording was chosen for readability. We will revise the Methods section to state explicitly that the parameters are held fixed across bands and will include a table listing the shared values. revision: yes
Referee: [Results] Results: The differences between objects are attributed to 'the value of the disk flux compared with the wall flux and the azimuthal variations of the former', but these are post-hoc fitted quantities; the manuscript does not show that the model makes a priori predictions independent of tuning to each lightcurve.

Authors: The flux ratios and azimuthal variations are indeed adjusted to match each lightcurve. The central claim is that one physical mechanism (the optically thick warp) simultaneously reproduces the correlated optical and infrared variability; object-to-object differences arise from the relative disk-to-wall flux and azimuthal structure. We will expand the discussion to clarify the fitting procedure and the limits of a priori prediction. revision: partial

Circularity Check

0 steps flagged

No circularity: standard model fitting to multi-band lightcurves

full rationale

The paper fits a parametric warp model (optically thick wall + asymmetric disk) to CoRoT and Spitzer data for four objects, reporting that amplitudes are reproduced and differences appear in fitted quantities such as disk-to-wall flux ratio and azimuthal extent. This is an explanatory fit, not a first-principles derivation whose output is forced to equal its inputs by construction. No equations reduce to self-definition, no fitted parameter is relabeled as an independent prediction, and no load-bearing self-citation or uniqueness theorem is invoked. The central claim remains an empirical demonstration that one geometric family can account for the observed resemblance between bands once parameters are adjusted; that adjustment is the expected content of such modeling work and does not constitute circularity.

Axiom & Free-Parameter Ledger

3 free parameters · 2 axioms · 0 invented entities

The model rests on several fitted geometric and flux parameters plus the domain assumption that the warp is optically thick; no new entities are postulated.

free parameters (3)

wall height / optical depth
Adjusted to produce the observed optical occultation depth for each object.
disk-to-wall flux ratio
Fitted separately for each star to match the relative IR amplitude.
azimuthal disk asymmetry amplitude
Varied to reproduce the shape differences between the four lightcurves.

axioms (2)

domain assumption The warp is optically thick at both optical and IR wavelengths.
Invoked in the methods to allow the wall to occult the star and the disk to emit without transmission.
ad hoc to paper A single warp structure accounts for all observed variability.
Stated as the aim; alternative variability sources are not quantitatively ruled out in the abstract.

pith-pipeline@v0.9.0 · 5781 in / 1568 out tokens · 25515 ms · 2026-05-25T16:44:19.122304+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Foundation/RealityFromDistinction.lean reality_from_one_distinction unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

We have modeled the infrared emission as coming from a warp composed of an optically thick wall and an optically thick asymmetric disk beyond this location. We have modeled the optical emission mainly by partial stellar occultation by the warp.
IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

The magnitude amplitude of the CoRoT and Spitzer observations for all the objects can be described with the emission coming from the system components. The difference between them is the value of the disk flux compared with the wall flux and the azimuthal variations of the former.

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

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