Capabilities of Searches for Supermassive Black Hole Binaries in Time-Domain Surveys

Supermassive black hole binaries (SMBHBs) are among the most promising sources for multi-messenger observations. In gravitational waves (GWs), they will be soon detectable by pulsar timing arrays (PTAs), whereas in electromagnetic (EM) surveys, more and more candidates are identified as AGN with periodic variability. By identifying host galaxies after GW detection, or by targeting candidates directly via their electromagnetic emissions, we will be able to perform multi-messenger explorations of these important players in the structure of the Universe. I will discuss how we disentangle flux-varying (doppler-boosted) SMBHB candidates from the noise in simulated variable AGN lightcurves and investigate which regions of SMBHB parameter space this binary identification method is sensitive to. By simulating current and future time-domain surveys, including those that will be done by the Vera C. Rubin Observatory, we visualize how these capabilities and limitations will shift in the coming years. By investigating the range of binary parameters that are able to be discovered in these surveys, we will be well prepared to search for likely hosts of a future nanohertz GW signal, and will build upon these methods to develop more multi-messenger techniques.