An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state

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Journal Title

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Volume Title

A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

Date

2021

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Mcode

Degree programme

Language

en

Pages

17
3912-3928

Series

Monthly Notices of the Royal Astronomical Society, Volume 496, issue 3

Abstract

Extreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at vs ≥ 1017 Hz. The BL Lac object 1ES 2344+514 was included in the EHBL family because of its impressive shift of the synchrotron peak in 1996. During the following years, the source appeared to be in a low state without showing any extreme behaviours. In 2016 August, 1ES 2344+514 was detected with the groundbased γ -ray telescope FACT during a high γ -ray state, triggering multiwavelength (MWL) observations. We studied the MWL light curves of 1ES 2344+514 during the 2016 flaring state, using data from radio to very-high-energy (VHE) γ -rays taken with OVRO, KAIT, KVA, NOT, some telescopes of the GASP-WEBT collaboration at the Teide, Crimean, and St. Petersburg observatories, Swift-UVOT, Swift-XRT, Fermi-LAT, FACT, and MAGIC. With simultaneous observations of the flare, we built the broad-band SED and studied it in the framework of a leptonic and a hadronic model. The VHE γ -ray observations show a flux level of 55 per cent of the Crab Nebula flux above 300 GeV, similar to the historical maximum of 1995. The combination of MAGIC and Fermi-LAT spectra provides an unprecedented characterization of the inverse-Compton peak for this object during a flaring episode. The _ index of the intrinsic spectrum in the VHE γ -ray band is 2.04 ± 0.12stat ± 0.15sys.We find the source in an extreme state with a shift of the position of the synchrotron peak to frequencies above or equal to 1018 Hz.

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Keywords

galaxies: active, BL Lacertae objects: individual: 1ES 2344+514, gamma-rays: galaxies, GAMMA-RAY EMISSION, OBSERVATORY SUPERNOVA SEARCH, SPECTRAL VARIABILITY, OBJECTS, CONNECTION, TELESCOPE, DISCOVERY, RADIATION, GALAXIES, MODELS

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Citation

Hovatta, T, MAGIC Collaboration, FACT Collaboration & MWL Collaborators 2021, ' An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state ', Monthly Notices of the Royal Astronomical Society, vol. 496, no. 3, pp. 3912-3928 . https://doi.org/10.1093/mnras/staa1702