ZTF DR24 gives a g-to-r magnitude change ratio of 0.98 for WD J0923+7326 in 20-day bins

Material near a white dwarf can block its light. The change in colour can help test models of this material. We measure the relation between slow ZTF g and r changes in the known debris candidate WD J0923+7326, Gaia DR3 1121123185951605632. We use frozen DR24 light curves, a correction from six nearby stars, and equal weights for sampled nights in 20-day bins. The 67 paired bins give a ratio of g to r magnitude changes of 0.979. Resampling occupied 60-day blocks gives a conditional central 95% range from 0.892 to 1.073. The middle 90% of bin magnitudes span 0.587 mag in g and 0.595 mag in r. The ratio is 0.988 with a fixed Pan-STARRS colour term and 0.948 with seeing at most 2.5 arcseconds. Some wider-bin and paired-night checks favour a ratio below one. The result supports similar slow amplitudes in these bands. It does not establish exact colour constancy. Two bands cannot determine grain size or separate opaque coverage from all dust models. This exploratory study provides a new measured relation for a known candidate. It does not identify a new planet or test the persistent extinction proposed from its parallax difference. The package preserves source responses, request hashes, code, results, figures, and instructions for an offline calculation.

white dwarf · WD J0923+7326 · ZTF DR24 · planetary debris · optical variability · colour variability · public data