ZTF data show no common brightening of 10 classical nova progenitors in the final year before eruption, and no precursor alert in the final 30 days of 22 novae (2018-2026)

Old photographic records show a pre-eruption rise in 2 of 22 novae (Collazzi et al. 2009). We tested this with ZTF data for the 63 Galactic novae in Koji Mukai's list that were discovered from 2018-06 to 2026-10 at declination above -31 degrees. In ZTF DR24 PSF light curves (to 2025-10), the same ZTF object that shows the eruption gives the progenitor light curve for 14 novae. Ten classical novae have enough data. The final-year median minus the earlier median has a median of +0.007 mag. Relative to neighbour stars of similar brightness at the same epoch, the median is -0.002 mag (95% interval -0.051 to +0.017 mag). No progenitor changed by 0.5 mag or more (0 of 10; 95% upper limit 31%). Thus our data cannot reject the Collazzi rate. V1674 Her became brighter by about 0.47 mag (g) over 4 years, at a slope steeper than all 20 neighbour stars, but mostly 2 to 3 years before eruption. Its ZTF object can contain light from a neighbour star. V6598 Sgr became brighter by about 0.3 mag over 3 years. V6596 Sgr was 0.2 to 0.4 mag fainter in its final observed season. In the ZTF public alert stream (ALeRCE), 22 novae with quiet progenitors had 260 covered nights in the 30 days before eruption (median 5-sigma limit 20.0 mag), and none gave a precursor alert. Two flagged detections were the start of the eruption. ZTF saw 3 eruptions 2.8 to 24.5 days before their catalogue discovery. Main limitations: the sample is small, the progenitors are faint and can be blended, DR24 ends before the 2026 eruptions, and seasonal gaps remove the final months of some bulge novae.

classical novae · nova progenitors · pre-eruption variability · precursor · ZTF · ALeRCE · cataclysmic variables · V1674 Her · V6596 Sgr · V8056 Sgr · time-domain astronomy · null result