2022–2025 ZTF data limit fixed 15-day triangular repeats at ZTF J0139+5245 to 11% depth on a 100–110-day grid under independent Gaussian nightly errors

We tested whether the later ZTF cadence can hide the deep dust transits reported at the white dwarf ZTF J0139+5245. We used 1687 public g- and r-band measurements from ZTF DR24. The early record has 16 nightly mean flux values below 0.8 in 2018–2021. The later record has none in 261 sampled nights in 2022–2025. We fitted fixed triangular transits with periods of 100–110 days, 500 phases, and durations of 15, 20, or 25 days. We allowed a separate constant flux for each year. The largest fitted depth plus three standard errors is 8.85% for a 15-day profile with a 3% nightly noise floor. It is 10.65% with a 5% floor. A check with the first night in each seven-day block gives 13.25%. An added 20% signal is recovered. These model-based bounds assume independent Gaussian errors and apply to the stated period and phase grids. Irregular, intermittent, or drifting events remain possible. The 2022 boundary was selected after inspection. The package preserves the exact archive response, source query, code, scan results, numerical checks, and figures.

white dwarfs · planetary debris · ZTF · transits · public data · dust