Calendario de Mauricio M. Perillo

Supermassive black hole binaries are thought to be an inevitable product of the prevailing galaxy evolution scenarios where most massive galaxies host a central black hole and undergo mergers over cosmic time. The early stages of this process have been observed in the form of interacting galaxy pairs and widely separated dual quasars, but the close, gravitationally bound binaries that are expected to follow have proven elusive. The detection of this population is important because at the smallest separations they become bright sources of low-frequency gravitational waves and are prime targets for multi-messenger detections with pulsar timing arrays (PTAs) and the upcoming Laser Interferometer Space Antenna (LISA). In this talk, I will discuss observational signatures of close binary supermassive black holes, especially in the context of regular quasar variability, and ongoing work towards multi-messenger detections with telescopes and gravitational wave detectors.