Abstract：Accreting supermassive black holes are known to be variable, changing in brightness across all wavelengths and timescales. In recent years, a remarkable subset of these Active Galactic Nuclei (AGN) has been discovered to show extreme spectral variability. These changing-look events can be caused by extreme and rapid changes in how fast the black hole is feeding, defying the expected accretion timescales for black holes with masses millions to billions solar masses. These rapid variations can allow us to gain unique insights on the accretion process in supermassive black holes.
With the upcoming Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), we expect to uncover thousands of these dramatic transformations, thanks to its combination of depth and rapid, repeated imaging of the sky. In this talk I will review what we have learned about changing-look AGN so far, and look ahead to how LSST, combined with new large-scale spectroscopic surveys such as 4MOST, will open a new era in our understanding of black hole variability.
Bio：Claudio Ricci is an Associate Professor at the University of Geneva (Switzerland) and a long-term visiting faculty at the Kavli Institute for Astronomy and Astrophysics in Beijing (China). He is a a member of the AAS Journals Editorial Board, where I serve as a Scientific Editor for The Astrophysical Journals.
Claudio’s research focuses on the accretion and obscuration of supermassive black holes, and how these processes shape the observed properties of active galactic nuclei. He uses X-ray spectroscopy and multiwavelength observations to study the structure and evolution of both the circumnuclear medium and the accretion flow. A central part of his recent work investigates changing-state AGN, where rapid transitions in spectral state provide key information on accretion physics. He is a co-founder and co-leader of the Swift/BAT AGN Survey (BASS), which is creating a benchmark sample of black hole accretion in the nearby Universe. Claudio is also involved in new photometric and spectroscopic surveys designed to trace black hole growth (LSST, 4MOST), with particular interest in rapid accretion events and the physics of super-Eddington accretion.