26–29 May 2026
Radisson Blu Marina Palace Hotel
Europe/Helsinki timezone

Variable and non-variable blazars at very high energies; comparison of fractional variability and SED peak properties

28 May 2026, 15:30
15m
Room B

Room B

Oral 28-B2: AGN

Speaker

Emma Johtela (University of Turku)

Description

Blazars, which are active galactic nuclei with relativistic jets pointing towards us, are among the most energetic phenomena in the universe. The radiation observed from blazars covers the entire electromagnetic spectrum, sometimes all the way up to the very-high-energy (VHE) gamma-rays, with energies over 100 GeV. Their VHE gamma-ray flux can vary by orders of magnitude on timescales as short as minutes, as such VHE emission can provide a direct view of the most extreme, rapidly evolving regions of relativistic jets. Interestingly, a subset of blazars appears to show no variability in the VHE regime. This could be an observational bias, or it could point to intrinsic physical differences between the sources. VHE gamma-rays can be detected with ground-based imaging air Cherenkov telescopes that image the Cherenkov light of particle showers triggered by a gamma-ray entering the atmosphere. For my project, I collected all the available VHE gamma-ray light curves of blazars from the literature and classified them into variable and non-variable sources. In this talk, I present the results of the differences between these two groups by comparing their fractional variability (in the optical, high-energy gamma-ray and VHE gamma-ray bands) as well as the peak frequencies of their Spectral Energy Distribution (SED).

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