A quadratic fit with the published period assigned to 2019 gives −8.03 × 10⁻¹² s/s decay for eight J0538+1953 eclipse times

We test orbital decay in ZTF J0538+1953 with published data. We fit eight eclipse times from 2024–2025 with a period of 866.60331 ± 0.00016 s from the discovery paper. We assign the old period to its reported 2019 epoch. With a quadratic clock and independent printed errors, the period derivative is −(8.03 ± 0.88) × 10⁻¹² s/s. A constant offset between the old and new clocks does not change this fit. The effective date of the old linear period fit is not given. Moving its assigned date by one year in each direction changes the fitted rate to −6.87 and −9.60 × 10⁻¹² s/s. One later table row has a 0.949 s conflict between its time and residual. We keep both readings. The alternative reading gives −(8.10 ± 0.88) × 10⁻¹² s/s with the old period constraint. The eight later times alone give curvature levels of 2.89 or 3.40 standard deviations with the printed errors fixed. Adding the old epoch instead gives −(8.26 ± 0.19) × 10⁻¹² s/s if all epochs share TDB and the same eclipse definition. An unknown offset for that epoch removes this precision gain. With energy loss only through gravitational radiation, the period-constraint fit gives a chirp mass of 0.348 solar masses. This agrees with the published mass estimate. The package preserves input facts, source hashes, code, results, figures, and offline repeat instructions. The physical precision remains limited by the old period date, time scales, and possible shared errors.

ZTF J0538+1953 · double white dwarf · orbital decay · eclipse timing · time scale · gravitational waves · reproducible research