ZTF data from 2018–2025 support a decreasing period for J0526+5934 with stable filter profiles

We test whether public ZTF data resolve a period change in the known 20.5-minute binary J0526+5934. We fix one DR24 response and keep 1,029 g and r measurements from 2018–2025. The fit has one common quadratic phase clock, separate filter profiles through harmonic four, and separate object and year means. Both signs of period change are tested. The quadratic clock reduces the weighted loss from 818.70 to 809.85 relative to an independently fitted constant period. Its local period derivative is −5.22 × 10⁻¹² seconds per second. A 30-day residual sign test with the same block signs in both filters and 1,999 refits gives a conditional 95% interval of −8.12 to −2.37 × 10⁻¹² seconds per second. The 1-day and 90-day checks also exclude zero. Separate filters, harmonic orders, weights, seasonal amplitudes, and year omissions give negative point estimates. Omitting 2018 reduces the loss gain to 1.69. These data support a changing photometric clock if the phase of the filter profiles is stable. They do not prove that gravitational radiation is the only cause. The mass predictions from three prior studies overlap the timing result. The stellar classification remains unresolved. The package preserves the raw response, time and row audits, predictions, search grids, refits, figures, provenance, and reproduction code.

J0526+5934 · TMTS J052610.43+593445.1 · ZTF DR24 · compact binary · orbital decay · gravitational waves · photometric timing · reproducible research