Broadband characterisation of the very intense TeV flares of the blazar 1ES 1959+650 in 2016
Authors:   MAGIC Collaboration, Acciari V. A. , Ansoldi S. , Antonelli L. A. , Arbet Engels A. , Baack D. , 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. , Biland A. , Blanch O. , Bonnoli G. , Bosnjak Z. , Busetto G. , Carosi R. , Ceribella G. , Chai Y. , 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. , Di Pierro F. , Do Souto Espiñeira E. , Dominis Prester D. , Donini A. , Dorner D. , Doro M. , Elsaesser D. , Fallah Ramazani V. , Fattorini A. , Fernández-Barral A. , Ferrara G. , Fidalgo D. , Foffano L. , Fonseca M. V. , Font L. , Fruck C. , Fukami S. , Gallozzi S. , García López R. J. , Garczarczyk M. , Gasparyan S. , Gaug M. , Godinović N. , Green D. , Guberman D. , Hadasch D. , Hahn A. , Herrera J. , Hoang J. , Hrupec D. , Inada T. , Inoue S. , Ishio K. , Iwamura Y. , Jouvin L. , Kubo H. , Kushida J. , Lamastra A. , Lelas D. , Leone F. , Lindfors E. , Lombardi S. , Longo F. , López M. , López-Coto R. , López-Oramas A. , Machado de Oliveira Fraga B. , Maggio C. , Majumdar P. , Makariev M. , Mallamaci M. , Maneva G. , Manganaro M. , Mannheim K. , Maraschi L. , Mariotti M. , Martínez M. , Masuda S. , Mazin D. , Mićanović S. , Miceli D. , Minev M. , Miranda J. M. , Mirzoyan R. , Molina E. , Moralejo A. , Morcuende D. , Moreno V. , Moretti E. , Munar-Adrover P. , Neustroev V. , Niedzwiecki A. , Nigro C. , Nilsson K. , Ninci D. , Nishijima K. , Noda K. , Nogués L. , Nöthe M. , Nozaki S. , Paiano S. , Palacio J. , Palatiello M. , Paneque D. , Paoletti R. , Paredes J. M. , Peñil P. , Peresano M. , Persic M. , Prada Moroni P. G. , Prandini E. , Puljak I. , Rhode W. , Ribó M. , Rico J. , Righi C. , Rugliancich A. , Saha L. , Sahakyan N. , Saito T. , Sakurai S. , Satalecka K. , Schweizer T. , Sitarek J. , Šnidarić I. , Sobczynska D. , Somero A. , Stamerra A. , Strom D. , Strzys M. , Surić T. , Takahashi M. , Tavecchio F. , Temnikov P. , Terzić T. , Teshima M. , Torres-Albà N. , Tsujimoto S. , van Scherpenberg J. , Vanzo G. , Vazquez Acosta M. , Vovk I. , Will M. , Zarić D. ,   Fermi-LAT Collaboration, Hayashida M. 
Published: March 2020

1ES 1959+650 is a bright TeV high-frequency-peaked BL Lac object exhibiting interesting features like “orphan” TeV flares and broad emission in the high-energy regime that are difficult to interpret using conventional one-zone Synchrotron Self-Compton (SSC) scenarios. We report the results from the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) observations in 2016 along with the multi-wavelength data from theFermiLarge Area Telescope (LAT) andSwiftinstruments. MAGIC observed 1ES 1959+650 with different emission levels in the very-high-energy (VHE,E >  100 GeV)γ-ray band during 2016. In the long-term data, the X-ray spectrum becomes harder with increasing flux and a hint of a similar trend is also visible in the VHE band. An exceptionally high VHE flux reaching ∼3 times the Crab Nebula flux was measured by MAGIC on the 13 and 14 of June, and 1 July 2016 (the highest flux observed since 2002). During these flares, the high-energy peak of the spectral energy distribution (SED) lies in the VHE domain and extends up to several TeV. The spectrum in theγ-ray (bothFermi-LAT and VHE bands) and the X-ray bands are quite hard. On 13 June and 1 July 2016, the source showed rapid variations in the VHE flux within timescales of less than an hour. A simple one-zone SSC model can describe the data during the flares requiring moderate to large values of the Doppler factors (δ ≥ 30−60). Alternatively, the high-energy peak of the SED can be explained by a purely hadronic model attributed to proton-synchrotron radiation with jet powerLjet ∼ 1046erg s−1and under high values of the magnetic field strength (∼100 G) and maximum proton energy (∼few EeV). Mixed lepto-hadronic models require super-Eddington values of the jet power. We conclude that it is difficult to get detectable neutrino emission from the source during the extreme VHE flaring period of 2016.