Most accepted J1539 primary eclipse exposures have no row in a frozen ZTF DR24 cone response

Does the public ZTF catalog retain the faint eclipse exposures of the known double white dwarf J1539? We compare one frozen light-curve cone response with calibrated images in the DR24 program and date scope for field 760, CCD 14, quadrant 3. Fixed-position aperture measurements accept 2,294 g- and r-band exposures from 2018–2025. A fixed published clock defines the primary eclipse window as absolute midpoint phase below 0.04. The response has rows for 12 of 94 g exposures and 5 of 98 r exposures in that window. Thus 175 of 192 accepted eclipse exposures, or 91.1 percent, have no returned row. The nearby flank window has coverage of 141/217 in g and 99/184 in r. In the planned 2-pixel aperture, mean g eclipse flux is 0.189 for all images and 0.285 for catalog-present images, where AB magnitude 20 has flux 1. The difference is 0.095, with a conditional 95-percent 30-day block interval of 0.041 to 0.148. The positive g contrast remains at radii 3 and 5 pixels. The r contrast depends on aperture size and only five returned exposures. Low eclipse coverage remains in both tested eras and image-depth halves. The result applies to the preserved response and selected images. Thirty-second integrations, background offsets, neighboring flux, and the fixed clock limit physical interpretation. These means are not intrinsic eclipse depths. The package preserves exact image and mask responses, provenance, code, fluxes including negative values, figures, resampling draws, and an offline reproduction check.

J1539 · ZTF · white dwarfs · eclipsing binaries · aperture photometry · catalog selection · missing measurements · public astronomical data