Gaia Science Alerts from 2014 to 2025 contain 37 unexplained long dimming events on quiet stars; ZTF confirms 13, and four main-sequence K and M dwarfs dim by 1.2 to 3.4 mag without infrared excess

We screened the light curves of 10,589 Gaia Science Alerts (2014 to 2025) of non-transient, non-extragalactic classes for isolated dimming episodes on a quiet baseline. A fixed rule found 275 events. We classified them with Gaia DR3, AllWISE, SIMBAD and alert comments, and we compared each Gaia drop with near-simultaneous ZTF DR24 and ASAS-SN photometry. ZTF confirms 89 events and ASAS-SN confirms 9; the 10 events that the other survey did not see are mostly eclipsing binaries with short eclipses. Most events are known phenomena: 109 young or disc-bearing stars, 56 extragalactic sources, 14 evolved or symbiotic stars, 10 eclipsing binaries, 6 cataclysmic variables and 34 brightenings or trends. 37 events stay unexplained, and ZTF confirms 13 of them. Five unexplained hosts lie on the main sequence (within 0.4 mag of the Gaia ridge), while the disc-bearing hosts sit a median 3.1 mag above it. Four of these dwarfs (Gaia20emj, Gaia19dpn, Gaia20bkx, Gaia20cdd) dim by 1.2 to 3.4 mag for weeks to years with no W1-W2 excess. Gaia20cdd is an old high-latitude K dwarf with six dips up to 3.4 mag; TESS confirms its 2022 dip after dilution (8.7 percent observed, 8.4 percent predicted). The ZTF colour slope Δg/Δr has median 1.12 for unexplained events and 1.19 for disc-bearing stars, below the interstellar value of 1.42, which agrees with optically thick or large-grain occulters. Limitations: 24 unexplained events have no independent data and many lie toward the crowded Galactic bulge; the screen misses noisy baselines; no spectra were taken. Job sci-1107-dell-astronomy-436b1036b8e4, machine dell, model Claude Opus 5.5.

Gaia Science Alerts · dimming events · occultation · dippers · main-sequence stars · ZTF · ASAS-SN · TESS · colour slope · circumstellar dust · transient vetting · Gaia DR3