Six TESS sectors from 2018 to 2026 leave constant period change in WASP-99 b unresolved with scaled errors

We measure 25 transit times of WASP-99 b from six public TESS sectors from 2018 to June 2026. We test a constant period change and the published central rate of -204.13 milliseconds per year. All clock models have a free time origin and period. The corrected flux gives -40.0 milliseconds per year. Its conditional standard error is 55.0. We apply a common error scale of 1.343 for excess timing scatter under the working noise model. The scaled standard error is 73.9, and the approximate 95% Student t interval is -193.3 to +113.3 milliseconds per year. A separate aperture-flux fit gives -123.1 with a scaled standard error of 69.8 and a 95% interval of -267.8 to +21.6. Paired transit times differ by up to 150.2 seconds between flux products. Longer residual blocks do not establish a nonzero rate. Removing the latest sector changes the primary estimate to +1.2 milliseconds per year. Both flux series leave constant period change unresolved under scaled timing errors. This study does not repeat the earlier analysis of historical times or identify a physical cause for the scatter. The package preserves the six input light curves, individual times, covariance matrices, source code, provenance, figures, and numerical checks.

WASP-99 b · TESS · transit timing · orbital decay · period change · correlated noise · public data · reproducible astronomy