Fits to 2018–2025 ZTF data with fixed profiles recover the period decrease in J0546+3843 but fail a J1858−2024 timing test
Can public survey data recover the reported opposite period changes in two known accreting white dwarf binaries? We test fixed light-curve profiles with 1,023 selected detections of ZTF J0546+3843 and 942 of ZTF J1858−2024 from 2018–2025. We check archive time conventions and convert exposure midpoints to BJD TDB. For J0546, the main fit gives a period derivative of −4.348 × 10⁻¹² s/s. The standard error with points grouped by UTC date is 0.837 × 10⁻¹² s/s. The derivative stays negative in the tested profile and sample controls. A clock fit through 2023 reduces weighted residual loss in 2024–2025 by 27.6% relative to a constant-period clock. For J1858, the preferred cycle count depends on the profile model. With one free phase offset, the main survey clocks give losses of 5.79 and 214.19 against the published fast timings for J0546 and J1858, respectively. The latter clock fails this timing test and does not give a reliable orbital derivative. These results apply to the selected survey detections and tested stable profiles. The survey data overlap the original study. This is not an independent confirmation. The package preserves raw responses, source hashes, time data, code, search grids, numerical results, figures, and offline instructions.
ZTF DR24 · AM CVn · white dwarf binaries · orbital timing · cycle aliases · barycentric time · public data · reproducible analysis
References
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This paper gives the target coordinates, reference periods, reported derivatives, and fast timings used for comparison. Some survey measurements overlap its data.
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We use its archive time audit and later-data test designs. We write new code and test the time effect for these targets.
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The ZTF Lightcurves service supplies the public measurements. Frozen responses and hashes define the exact sample because this service DOI has no version field.
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This paper describes the ZTF data system, products, and archive.
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This work explains the time scales and reference origins needed for the timing audit.
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Astropy supplies the coordinate and time tools used to prepare the data.
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This catalogue gives context for known white dwarf binaries with mass transfer. We do not use its measurements in the fits.
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