Yuri Kovalev - Very-High-Energy Blazars at Parsec Scales

Friday 21 Nov 2025, 10:30 → 12:00 Europe/Berlin

Active galactic nuclei (AGN) are among the most powerful sources in the Universe, dominating the non-thermal energy output across nearly all electromagnetic bands. Understanding the mechanisms behind this emission, such as accretion onto supermassive black holes, particle acceleration, and shock formation in relativistic plasma, is essential for interpreting high-energy and multi-messenger observations. These processes are best probed through coordinated studies combining very-high-energy and high-angular-resolution observations.
Growing observational evidence for neutrino production in AGN is shedding new light on proton acceleration mechanisms, whether near supermassive black holes or within shocks embedded in relativistic jets. We find that relativistic beaming is a crucial factor in neutrino emission from blazars, suggesting that their parent PeV-scale protons exhibit relativistic bulk motion. We also find that blazars viewed at extremely small angles to the line of sight can naturally resolve the long-standing "Doppler factor crisis," reconciling the low apparent jet speeds from VLBI with the high Doppler factors inferred from very-high-energy observations. Our results highlight the central role of relativistic beaming in shaping the gamma-ray and neutrino emission of blazars and offer new constraints for models of their multi-messenger output.