Determine the mechanisms powering AGN nuclear transients

Determine the physical mechanisms responsible for the observed classes of AGN-related nuclear transients—namely changing-look AGN, changing-state AGN, periodic AGN, quasi-periodic eruptors, quasi-periodic oscillators, ambiguous nuclear transients, extreme nuclear transients, and tidal disruption events—and ascertain to what extent interactions between AGN accretion disks and stars from nuclear star clusters account for these phenomena.

Background

The paper summarizes that AGN exhibit diverse nuclear transient phenomena (e.g., changing-look and changing-state AGN, QPEs, QPOs, ANTs, ENTs, and TDEs) that are currently classified phenomenologically by timescales, energetics, and spectral behavior. Despite extensive monitoring from wide-field time-domain surveys, the underlying physical drivers of these phenomena are not well established.

The authors present J2245+3743, an extreme, highly energetic nuclear flare, and discuss multiple plausible mechanisms (including AGN TDEs, supernovae within disks, and gravitational lensing). The difficulty in uniquely attributing events like J2245+3743 underscores the broader unresolved question of what physical processes power different AGN nuclear transient classes and when disk–star interactions dominate.