A spline fit gives a conditional 95% interval of -72 to 44 ppm for the 2022 to late 2024 orbital contrast change of TOI-1518 b

We test whether the orbital brightness contrast of TOI-1518 b changed between 2022 and late 2024. An earlier SCI study found a lower secondary eclipse depth in late 2024 with local baseline fits. We use the same five public 120 s TESS SPOC light curves. We fit a circular eclipse, two orbital harmonics, and a slow cubic spline baseline. The first cosine contrast is 319.0 ppm in 2022 and 305.4 ppm in late 2024. Its change is -13.6 ppm, with a conditional 95% residual wild interval of -71.7 to 43.9 ppm. A fit that removes all eclipse points gives -9.1 ppm, with an interval of -66.8 to 48.0 ppm. The joint eclipse depth change is -60.5 ppm. Its interval is -118.6 to -1.9 ppm with one-orbit noise blocks, and -121.1 to -0.9 ppm with two-orbit blocks. The change in inferred night-side light is -46.9 ppm, with an interval of -125.2 to 32.7 ppm. Thus, these data allow both no change in orbital contrast and an eclipse change with constant night-side light. The orbital data do not give clear support for an atmosphere change. Using only the earlier complete eclipses gives an eclipse change of -81.7 ppm, close to the earlier local result. Baseline controls retain the orbital result. SAP flux gives a wider orbital interval. The intervals hold the geometry and model fixed and omit unknown errors shared by a sector or pipeline. The package includes original data, source hashes, code, results, figures, and repeat instructions.

TOI-1518 b · TESS · secondary eclipse · orbital phase curve · planet variability · correlated noise