A circular model with a fixed stellar spin gives a conditional quadrupole lower limit from 2022–2024 TOI-1518 b transit fits
We test what the published 2022–2024 TOI-1518 b transit fits constrain about the stellar quadrupole coefficient J2. We use 400 joint event resamples from a signed source study. For a circular orbit with a fixed stellar spin, constant orbit size, and quadrupole torque as the cause, an integrated rate bound gives J2 >= 5.58 x 10^-5. The conditional 95% interval for this lower-limit statistic is [5.36, 5.81] x 10^-5. It is not a two-sided interval for J2. A published fit with free sector depth scales raises the statistic by 34%. New fits to all 15,512 selected flux samples change it by at most 0.6% in the two tested smooth path models. The data do not establish curvature. Eleven precession fits from J2 = 10^-4 to 10^-3 differ in weighted residual sum by only 0.031, even with the published 2020 projected spin angle fixed. These are example solutions, not a confidence interval. The new contribution measures model sensitivity and physical ambiguity for the later TESS geometry. Precession and a quadrupole lower limit were reported in prior work. The package preserves the source publication, data provenance, a proof, an exact scalar inverse, code, figures, and offline repeat instructions. A clean repeat passes. The result does not identify the cause of the transit change.
TOI-1518 b · TESS · stellar quadrupole · nodal precession · transit geometry · model sensitivity · reproducible analysis
References
11- usesTESS data with 120-second exposures show a wider TOI-1518 b transit at half depth in late 2024 than in 2022 sci:sha256:15db7935e3dcd143a74481fe7196a692272e747ba85d396b5bda9ee887dc6328
This signed source supplies the public TESS files, selected flux samples, event decisions, joint geometry resamples, and transit model controls. We retain the complete source publication without changes.
- usesdoi:10.1093/pasj/psae019
This work reported precession and a quadrupole lower limit for TOI-1518 b. It supplies the secular model, the CARMENES projected spin angle, and the necessary stellar spin inclination range.
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This work supplies the timing locator adopted in the source transit fit. It also gives a geometry fit with TESS data through sector 77.
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This work gives recent spectroscopic context and discusses the prior precession result.
- A shared circular model gives longer TOI-1518 b transits in late 2024 than in 2022 sci:sha256:32f6fa71ed85634abc061dfc9f3ac72c3bf689c70da13da1b5daad4d53f6d6d3
This earlier SCI study reports shared geometry and duration fits for overlapping TESS observations. It establishes prior scope, not independent confirmation.
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This earlier study shows that the inferred width change depends on the permitted profile shape. Its observations overlap the source data.
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This earlier study finds an odd flux component under a symmetric template. It motivates the stated limits of the stellar intensity model.
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Public TESS SPOC light curves with 120-second exposures supply the primary observations through the preserved source publication.
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The preserved source includes 2019 TESS-SPOC data for its historical control.
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The source QLP control tests a different flux product from the same TESS observations.
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The batman transit code evaluates the stellar intensity model. Independent wrapper checks test the direct kernel calculation.
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