Description
The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will monitor tens of millions of active galactic nuclei (AGNs) over a period of 10 years, with an average cadence of 3 days across six broad photometric bands. This unprecedented dataset will enable robust characterizations of AGN UV/optical variability across a wide range of AGN physical properties. However, existing tools for modeling AGN UV/optical continuum variability and inter-band time delays are not scalable to the data volumes of LSST. We present EzTaoX, a time series modeling tool that can leverage LSST multi-band light curves to jointly infer AGN UV/optical stochastic variability properties and the time delays between photometric bands. EzTaoX achieves a speedup of 10²–10³ compared to existing tools while delivering the same level of accuracy. This speedup enables the measurement of inter-band continuum time delays for all AGNs discovered by LSST, opening up new opportunities to investigate accretion flow geometries in AGNs. In addition, EzTaoX's multi-band capability allows for more robust characterization of AGN stochastic variability down to hourly timescales, enabling the selection of accreting intermediate-mass black holes based on their unique variability properties.
