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

Extreme High-frequency BL~Lacs (EHBL) feature their synchrotron peak of the broadband spectral energy distribution (SED) at ${\nu }_{\mathrm{s}}\ge$10${}^{17}$,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 August 2016, 1ES~2344+514 was detected with the ground-based $\gamma$-ray telescope FACT during a high $\gamma$-ray state, triggering multi-wavelength (MWL) observations. We studied the MWL light curves of 1ES~2344+514 during the 2016 flaring state, using data from radio to VHE $\gamma$ rays taken with OVRO, KAIT, KVA, NOT, some telescopes of the GASP-WEBT collaboration at the Teide, Crimean, and St. Petersburg observatories, $\mathit{\text{Swift}}$-UVOT, $\mathit{\text{Swift}}$-XRT, $\mathit{\text{Fermi}}$-LAT, FACT and MAGIC. With simultaneous observations of the flare, we built the broadband SED and studied it in the framework of a leptonic and an hadronic model. The VHE $\gamma$-ray observations show a flux level of 55% of the Crab Nebula flux above 300,GeV, similar to the historical maximum of 1995. The combination of MAGIC and $\mathit{\text{Fermi}}$-LAT spectra provides an unprecedented characterization of the inverse-Compton peak for this object during a flaring episode. The $\mathrm{\Gamma }$ index of the intrinsic spectrum in the VHE $\gamma$-ray band is $2.04\pm {0.12}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}}\pm {0.15}_{\mathrm{s}\mathrm{y}\mathrm{s}}$. We find the source in an extreme state with a shift of the position of the synchrotron peak to frequencies above or equal to ${10}^{18}$,Hz