Ponente
Descripción
Extreme high-synchrotron-peaked blazars (EHSPs), defined by synchrotron peaks above 10^17 Hz, represent an uncommon subclass of blazars that challenge conventional blazar emission models and probe the limits of particle acceleration in relativistic jets. Yet, the number of identified EHSPs remains small, limiting comprehensive studies of their population and physical characteristics. In this contribution, we present a systematic study aimed at identifying and characterizing new EHSP candidates using a sample of 124 gamma-ray blazars selected from a wider catalogue based on their high synchrotron peak frequencies, low variability, and good broadband data coverage. The spectral energy distributions (SEDs) of the sample blazars are built using archival data complemented by Swift and Fermi-LAT observations, and modelled within a one zone synchrotron/synchrotron-self-Compton (SSC) framework. We identify 66 new EHSP candidates, significantly expanding the known population. A clear correlation emerges between synchrotron peak frequency and the magnetic-to-kinetic energy density ratio, with the most extreme sources approaching equipartition. This indicates that as the synchrotron peak shifts to higher frequencies, the energy stored in the magnetic field becomes comparable to that of the relativistic electrons, suggesting a more balanced and energetically efficient jet environment in the most extreme blazars. Our results suggest that 9 high-synchrotron peaked/EHSPs could be detected by the Cherenkov Telescope Array Observatory (CTAO) above 5σ significance (and 20 above 3σ) in 20-hour observations, implying that while the overall detection rate remains modest, a subset of these sources is within reach of next-generation very-high-energy gamma-ray instruments.
