| Abstract: Inspiraling supermassive black hole binaries (SMBHBs), expected products of galaxy mergers and strong low-frequency gravitational-wave sources, are difficult to resolve at sub-parsec scales. Their orbits may instead be traced through periodic or chirping AGN variability, including relativistic Doppler boosting. I will present optical-survey methods combining accretion-flow models with Bayesian chirp detection. My results suggest that mixtures of mini-disk and circumbinary-disk emission are present in observations by Rubin’s LSST. In PTF, a Bayesian chirp-plus-noise search finds 33 apparent multi-cycle fits among 35,383 quasars, but none remains phase-coherent with extended ASAS-SN and ZTF data. Ten-year LSST simulations recover chirps across broad merger-time and amplitude ranges under the assumed models. However, mini-disks may be more visible in UV/X-rays for many systems considered, motivating broad, deep surveys to probe more binary parameter space. |