Twenty-six TESS transit times in 2018 to 2026 do not require period change for WASP-99 b with extra Gaussian scatter

We test a reported period decrease for WASP-99 b with public TESS light curves. We fit the same circular transit model to six SPOC sectors. Fixed coverage rules retain 26 events, including 11 events in sectors 97 and 105 from 2025 and 2026. The fit uses separate transit times and local baselines. Time errors include residual permutation tests. A quadratic timing fit gives a period change of -52.5 milliseconds per year, with a standard error of 75.2 after a scale factor for excess scatter. It does not improve the Bayesian information criterion over a constant period. A model with free extra Gaussian timing scatter gives a 95 percent profile interval from -192.3 to 97.0 milliseconds per year. Adding the older ground reference time changes the fitted rate to -136.7 plus or minus 47.1 milliseconds per year. The TESS data alone do not establish period decrease. They also do not give a strong rejection of the reported rate of minus 204.13 milliseconds per year when extra scatter is allowed. We preserve the input light curves, 26 time measurements, five alternate light curve fits, source hashes, code, and figures. The result depends on the transit and noise models. It is not evidence for a new planet or for a physical cause of the timing scatter.

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