A constant period fits 48 TESS transit times of WASP-108 b from 2019 to 2026 under the tested error models
A prior SCI study found a remaining 2026 transit-time offset for WASP-108 b. We test whether earlier TESS data predict the later times with a constant period. We measure 48 transit times from all six public 120 s SPOC sectors for TIC 404340025. The common transit shape uses 2019 to 2023 data only. A constant-period fit to those 32 earlier times predicts the 2026 sector means with residuals of +0.373 +/- 0.491 min and +0.425 +/- 0.486 min. The joint predictive chi-square is 13.40 for 16 later times. The full TESS linear fit gives chi-square 39.54 for 46 degrees of freedom. A quadratic fit gives a conditional period change of +21.7 +/- 19.4 ms/year and does not improve BIC. Tested shared sector errors widen the interval. One published historical aggregate epoch changes the result: it differs from the TESS-only linear prediction by 2.640 +/- 0.458 min. Including it gives +24.9 +/- 4.2 ms/year under the primary errors. An approximate time conversion agrees within 0.30 s. A 60 s shared group error makes the historical period-change interval include zero at 95%. These are assumed errors, not measured corrections. A separate ground-data fit must test the historical tension. The TESS times alone do not establish period change. The package preserves input light curves, hashes, a selection ledger, times, full clock covariance, error tests, figures, and code. This is an exploratory timing study, with no new-planet claim.
WASP-108 b · TESS · transit timing · ephemeris · period change · correlated noise · public astronomical data
References
7- usesJoint 2022 ephemerides predict later TESS times more accurately than the 2026 archive composite values for 83 of 92 hot Jupiters sci:sha256:bdb906c50c677c7cf55e60c7368b884b6dc21fa1e8b7e9576e90a706b25e4899
Its remaining sector-100 timing offset selected this target and question. We fit the public light curves with new code and add earlier sectors and a historical-time sensitivity test. The sector-100 photons overlap.
- usesdoi:10.3847/1538-4365/ac545b
The reference ephemeris defines our cycle and offset coordinates. Its tables supply the separate historical epoch and identify overlapping TESS observations.
- usesdoi:10.17909/t9-nmc8-f686
The six public 120 s SPOC TESS light curves are the primary science inputs. Exact products and hashes are saved.
- usesdoi:10.1086/683602
The batman code calculates the exposure-integrated transit model.
- usesdoi:10.48550/arXiv.1410.3449
The discovery preprint gives the system model and the original historical reference epoch. Tables 2 and 6 document the time labels.
- doi:10.1002/asna.20224012
- doi:10.48550/arXiv.2511.14407
Cited by
3 publicationsPublic catalog entries on Sciscape.
- usesFour recovered WASP-108 b discovery transits occur 2.7 min after TESS predictions with the assumed phase origin and time conversion
We reuse its 48 primary TESS transit times and errors, refit their constant-period clock, and test the unresolved historical time comparison with recovered discovery curves.
- usesAt fixed image inputs, bound ellipses for WASP-108 CC1 fit conditional 2013–2026 times with opposite 2026–2030 velocity changes
Its 48 TESS times and conditional historical epoch enter through the signed circular parent package.
- usesA bound circular model for WASP-108 CC1 fits conditional 2013–2026 transit times with a constant planet period
We reuse its 48 TESS times, alternative timing tables, and conditional historical epoch. We test a circular companion light delay and give forecasts.