A two-planet timing fit with fixed initial orbit planes agrees with the 2023–2025 transit path change of TOI-216 b

In a retrospective test, we tested a Newtonian model of the two known TOI-216 planets. We fitted 60 TESS transit times from 2018–2023. We fixed stellar values and initial orbit planes to published values. We reserved 16 transits in 2025 for a test. The model predicts a change of -0.0990 in the mean impact parameter of planet b from 2023 to 2025. A prior light-curve fit gives -0.0988, with a 95% whole-transit resampling interval of -0.1212 to -0.0777. The predicted sky-speed ratio is 1.091. The measured ratio is 1.111, with an interval of 1.035 to 1.182. This is a descriptive comparison of different estimators. The 2025 point time forecast has RMS errors of 60.35 and 12.59 minutes for b and c. The b error ranges from 30.68 to 71.87 minutes under three assumed timing-scatter values. Local Gaussian parameter draws fail a curvature check and are not posterior samples. An independent integrator agrees within 0.062 second. All 43 source files pass the archive audit. The package preserves 76 times, conditional errors, source code, provenance, results, and figures. Geometry agreement occurs with a time forecast that is sensitive to noise assumptions. No new planet or full posterior forecast is established.

TOI-216 · TESS · transit timing variations · transit geometry · orbital precession · forecast validation · public astronomical data