An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state
Authors: Acciari MAGIC Collaboration: V A , Ansoldi S , Antonelli L A , Arbet Engels A , Babić A , Banerjee B , Barres de Almeida U , Barrio J A , Becerra González J , Bednarek W , Bellizzi L , Bernardini E , Berti A , Besenrieder J , Bhattacharyya W , Bigongiari C , Blanch O , Bonnoli G , Bošnjak Ž , Busetto G , Carosi R , Ceribella G , Cerruti M , Chai Y , Chilingaryan A , Cikota S , Colak S M , Colin U , Colombo E , Contreras J L , Cortina J , Covino S , D’Elia V , Da Vela P , Dazzi F , De Angelis A , De Lotto B , Delfino M , Delgado J , Depaoli D , Di Pierro F , Di Venere L , Do Souto Espiñeira E , Dominis Prester D , Donini A , Doro M , Elsaesser D , Fallah Ramazani V , Fattorini A , Ferrara G , Foffano L , Fonseca M V , Font L , Fruck C , Fukami S , García López R J , Garczarczyk M , Gasparyan S , Gaug M , Giglietto N , Giordano F , Godinović N , Gliwny P , Green D , Hadasch D , Hahn A , Herrera J , Hoang J , Hrupec D , Hütten M , Inada T , Inoue S , Ishio K , Iwamura Y , Jouvin L , Kajiwara Y , Kerszberg D , Kobayashi Y , Kubo H , Kushida J , Lamastra A , Lelas D , Leone F , Lindfors E , Lombardi S , Longo F , López M , López-Coto R , López-Oramas A , Loporchio S , Machado de Oliveira Fraga B , Maggio C , Majumdar P , Makariev M , Mallamaci M , Maneva G , Manganaro M , Maraschi L , Mariotti M , Martínez M , Mazin D , Mender S , Mićanović S , Miceli D , Miener T , Minev M , Miranda J M , Mirzoyan R , Molina E , Moralejo A , Morcuende D , Moreno V , Moretti E , Munar-Adrover P , Neustroev V , Nigro C , Nilsson K , Ninci D , Nishijima K , Noda K , Nogués L , Nozaki S , Ohtani Y , Oka T , Otero-Santos J , Paiano S , Palatiello M , Paneque D , Paoletti R , Paredes J M , Pavletić L , Peñil P , Peresano M , Persic M , Prada Moroni P G , Prandini E , Puljak I , Ribó M , Rico J , Righi C , Rugliancich A , Saha L , Sahakyan N , Saito T , Sakurai S , Satalecka K , Schleicher B , Schmidt K , Schweizer T , Sitarek J , Šnidarić I , Sobczynska D , Spolon A , Stamerra A , Strom D , Strzys M , Suda Y , Surić T , Takahashi M , Tavecchio F , Temnikov P , Terzić T , Teshima M , Torres-Albà N , Tosti L , van Scherpenberg J , Vanzo G , Vazquez Acosta M , Ventura S , Verguilov V , Vigorito C F , Vitale V , Vovk I , Will M , Zarić D , Baack FACT Collaboration: D , Balbo M , Beck M , Biederbeck N , Biland A , Blank M , Bretz T , Bruegge K , Bulinski M , Buss J , Doerr M , Dorner D , Hildebrand D , Iotov R , Klinger M , Mannheim K , Achim Mueller S , Neise D , Neronov A , Nöthe M , Paravac A , Rhode W , Schleicher B , Sedlaczek K , Shukla A , Sliusar V , Tani L , Theissen F , Walter R , Acosta Pulido MWL Collaborators: J , Filippenko A V , Hovatta T , Kiehlmann S , Larionov V M , Max-Moerbeck W , Raiteri C M , Readhead A C S , Šegon M , Villata M , Zheng W 
Published: June 2020

Extreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at νs ≥ 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 ground-based 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 Γ 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.