The 2018–2025 ZTF flux fits support a period decrease for J0538+1953 with the tested stable profiles

We test the reported period decrease of the known eclipsing double white dwarf ZTF J0538+1953 with independent public ZTF DR24 detections. The sample has 674 accepted exposures from 2018 to 2025. We fit a common quadratic clock, separate Fourier profiles for each filter, and separate flux levels for each filter and season. All tested profiles for the full sample with 4 to 12 harmonics support a period decrease. The fitted rates range from −15.00 to −9.34 × 10⁻¹² seconds per second. The H6 main fit gives −12.98 × 10⁻¹², with a conditional 95% interval of −14.82 to −10.31 × 10⁻¹² from residual sign simulations with 30-day blocks. The 30-second H12 fit gives −9.52 × 10⁻¹². The rate has not converged with profile order. Early H6 fits select a period increase and fail on later data. An early H12 fit selects a decrease and reduces the later weighted squared error by 57.5% relative to a constant clock. Only additive later levels are calibrated. A separate fit to eight published eclipse times gives −(9.15 ± 3.16) × 10⁻¹² with their listed errors. The ZTF result supports the sign of the reported change under stable profiles. It does not give a precise rate that is independent of the profile model. Missing faint detections, profile changes, and calibration can bias the result. The package preserves raw data, provenance, code, clock searches, controls, predictions, simulations, figures, and offline reproduction instructions.

ZTF J0538+1953 · double white dwarf · orbital period · Zwicky Transient Facility · public astronomical data · eclipse timing · Fourier profiles · reproducible research