Title:  Supermassive binary black holes in galactic centers: theoretical and observational perspectives

　　Speaker: Youjun Lu (NAOC)

　　Time: Thursday, 3:00pm, April 24th

　　Location: Lecture Hall, 3rd floor

　　The study of supermassive binary black holes (BBHs) is of great importance for various topics in physics and astrophysics, including detection of gravitational waves and cosmic evolution of galaxies and supermassive black holes (SMBHs). Formation of BBHs in galactic centres is an inevitable consequence of hierarchical mergers of galaxies in the standard LambdaCDM cosmology and BBHs may be abundant. However, direct observational evidence for the existence of BBHs remains elusive. I will review the orbital evolution of BBHs and the characteristic observational features of BBHs at different evolutionary stages and how these features can be used to identify BBHs, focusing on a few probes that we proposed. I will also summarise previous and ongoing efforts in searching BBHs and discuss how the current observations, specifically on the frequency of dual AGNs, can be used to constrain the evolution of BBHs and the triggering mechanism of nuclear activities.