Six TESS transit times of TOI-2257 b agree with a constant period in 2019–2022 under a fixed transit shape

We test whether later public TESS observations show a change in the transit times of TOI-2257 b. Eleven sectors through Sector 75 contain six complete transits from 2019 to 2022. The 2024 data miss the predicted transits. We measure each time with a fixed transit shape, a free depth, and a local linear baseline. We use the larger of the formal error and residual bootstrap errors from 10, 30, and 60 minute blocks. A constant period gives chi-square 1.17 for four degrees of freedom. The period is 35.18931362 days, with a standard error of 23.4 seconds. The four later events agree with the published clock. Under independent Gaussian timing errors and random event offsets, a bound that retains all measurement variance gives a conditional 95% upper limit of 16.4 minutes on extra timing scatter. This bound does not apply to all periodic timing changes or to other planets. The package contains the source light curves, checksums, six transit times, fit controls, figures, and code. The TESS-only clock is an independent check. It is less precise than the published clock that also used ground observations.

TOI-2257 b · TESS · transit timing · public data · reproducible research