Abstract: Turbulent coronae around supermassive black holes can accelerate non-thermal particles to high energies and power observable emission, but the comparable timescales of acceleration, cooling, and electromagnetic cascades make this process hard to capture. In this seminar, I’ll introduce a time-dependent framework that self-consistently couples proton acceleration—modeled with a Fokker–Planck equation—to lepto-hadronic radiation and cascading. Applied to the neutrino-emitting active galactic nucleus (AGN) NGC 1068, the model reproduces IceCube’s observed neutrino spectrum while remaining consistent with gamma-ray limits. I’ll also discuss a transient-corona scenario, potentially arising in non-jetted tidal disruption events such as AT 2019dsg, where early cascade feedback regulates proton acceleration in weaker coronae and imprints delayed optical/UV, X-ray, and neutrino signals on ~100-day timescales. The framework efficiently models multi-messenger emission from both steady and transient sources, offering a flexible way to connect particle-acceleration physics with radiation mechanisms in AGN and TDE environments.
Bio: Dr. Chengchao Yuan is currently a Postdoctoral Fellow at Deutsches Elektronen-Synchrotron (DESY), where he primarily engages in theoretical and numerical particle astrophysics and multi-messenger astronomy. His research encompasses the acceleration, propagation, and radiation mechanisms of cosmic rays, as well as the origins and interconnections between cosmic rays, astrophysical neutrinos, and gamma rays. His work focuses on various astrophysical sources, including active galactic nuclei (AGN), tidal disruption events (TDE), gamma-ray bursts (GRB), compact star mergers, and galaxies and galaxy clusters. Dr. Yuan earned his Ph.D. in Physics from Pennsylvania State University in 2022, after obtaining a Bachelor's degree in Astronomy from Nanjing University in 2016.