Volume 501 - 39th International Cosmic Ray Conference (ICRC2025) - Gamma-Ray Astrophysics
Long-term multiwavelength view and modeling of the blazar B2 1811+31 in high state
D. Cerasole*, S. Loporchio  on behalf of the Fermi-LAT and MAGIC collaborations and  On behalf of multiwavelength collaborators
*: corresponding author
Full text: pdf
Pre-published on: September 23, 2025
Published on: —
Abstract
Intermediate synchrotron-peaked BL Lacs (IBLs) are quite rare sources in the very high-energy
(VHE; 100 GeV < E < 100 TeV) 𝛾-ray sky. The IBL B2 1811+31 (𝑧 = 0.117) showed intense
flaring activity in 2020. This event was detected by a wide range of multiwavelength (MWL)
instruments from radio up to 𝛾 rays. The observations carried out by the MAGIC telescopes led
to the first-time detection of VHE 𝛾-ray emission from B2 1811+31.
In this contribution, we highlight the key results of our recent study [1], which offers a compre-
hensive analysis of the source emission both during the 2020 high-activity state and during the
quiescent state. Using a comprehensive MWL dataset, we contextualize this high-state episode
within the source emissions over 18 years, from 2005 to 2024. We attribute the VHE 𝛾-ray emis-
sion and the spectral and variability properties in the X-ray band to the electrons and positrons
accelerated at the highest energies in the jet of the source. We propose a leptonic two-zone
self-consistent model to interpret the observed MWL emission during the 2020 flaring state.
DOI: https://doi.org/10.22323/1.501.0599
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