QhX Catalog of Coherent and Quasi-coherent Active Galactic Nucleus Variability from Vera C. Rubin LSST DP1

Coherent and quasi-coherent variability in active galactic nuclei (AGN) can serve as a useful diagnostic of dynamical processes operating in the immediate environments of supermassive black holes. The time-domain capabilities of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) enable systematic searches for such signals across large AGN samples. We identify and classify coherent oscillatory processes in AGN cores using LSST Data Preview 1 (DP1), and compile the results in the QhX Hub, an interactive catalog providing statistical variability features and visualization tools. AGN are selected by cross-matching LSST DP1 sources with external catalogs, and light curves are analyzed with the multiband wavelet-based Quasar harmonic eXplorer ( QhX ), designed to detect coherent signals in irregularly sampled, red-noise-dominated data. The catalog contains 230 objects stratified into variability classes. A single strong coherent candidate is identified: 3D-HST 2351, z = 0.198, LSST DP1 object_id = 611255072642321324, with a period of P = 2.7 6 − 0.06 + 2.65 days, where the large upper bound reflects the limited observational baseline. Its coherent nuclear variability is the primary motivation for follow-up. In subsequent LSST data releases, all catalog sources will be recalculated on progressively longer baselines, enabling more robust population-level characterization of coherent AGN variability.