New Hard-TeV Extreme Blazars Detected with the MAGIC Telescopes*
Authors: Acciari V. A. , Ansoldi S. , Antonelli L. A. , Engels A. Arbet , Asano K. , Baack D. , Babić A. , Banerjee B. , de Almeida U. Barres , Barrio J. A. , González J. Becerra , Bednarek W. , Bellizzi L. , Bernardini E. , Berti A. , Besenrieder J. , Bhattacharyya W. , Bigongiari C. , Biland A. , 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. , Vela P. Da , Dazzi F. , Angelis A. De , Lotto B. De , Delfino M. , Delgado J. , Depaoli D. , Pierro F. Di , Venere L. Di , Souto Espiñeira E. Do , Prester D. Dominis , Donini A. , Dorner D. , Doro M. , Elsaesser D. , Ramazani V. Fallah , Fattorini A. , Ferrara G. , Fidalgo D. , Foffano L. , Fonseca M. V. , Font L. , Fruck C. , Fukami S. , López R. J. García , Garczarczyk M. , Gasparyan S. , Gaug M. , Giglietto N. , Giordano F. , Godinović N. , Green D. , Guberman D. , Hadasch D. , Hahn A. , Herrera J. , Hoang J. , Hrupec D. , Hütten M. , Inada T. , Inoue S. , Ishio K. , Iwamura Y. , Jouvin L. , Kerszberg D. , 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. , de Oliveira Fraga B. Machado , Maggio C. , Majumdar P. , Makariev M. , Mallamaci M. , Maneva G. , Manganaro M. , Mannheim K. , Maraschi L. , Mariotti M. , Martínez M. , 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. , Nigro C. , Nilsson K. , Ninci D. , Nishijima K. , Noda K. , Nogués L. , Nozaki S. , Paiano S. , Palatiello M. , Paneque D. , Paoletti R. , Paredes J. M. , Peñil P. , Peresano M. , Persic M. , Moroni P. G. Prada , Prandini E. , Puljak I. , Rhode W. , Ribó M. , Rico J. , Righi C. , Rugliancich A. , Saha L. , Sahakyan N. , Saito T. , Sakurai S. , Satalecka K. , Schmidt K. , Schweizer T. , Sitarek J. , Šnidarić I. , Sobczynska D. , Somero 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. , Vagelli V. , Scherpenberg J. van , Vanzo G. , Acosta M. Vazquez , Vigorito C. F. , Vitale V. , Vovk I. , Will M. , Zarić D. , Arcaro C. , Carosi A. , D’Ammando F. , Tombesi F. , Lohfink A. 
Published: February 2020

Abstract
Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature nonthermal gamma-ray emission whose peak lies in the very high-energy (VHE, E > 100 GeV) range, and in some sources exceeds 1 TeV: this is the case for hard-TeV EHBLs such as 1ES 0229+200. With the aim of increasing the EHBL population, 10 targets were observed with the MAGIC telescopes from 2010 to 2017, for a total of 265 hr of good-quality data. The data were complemented by coordinated Swift observations. The X-ray data analysis confirms that all but two sources are EHBLs. The sources show only a modest variability and a harder-when-brighter behavior, typical for this class of objects. At VHE gamma-rays, three new sources were detected and a hint of a signal was found for another new source. In each case, the intrinsic spectrum is compatible with the hypothesis of a hard-TeV nature of these EHBLs. The broadband spectral energy distributions (SEDs) of all sources are built and modeled in the framework of a single-zone, purely leptonic model. The VHE gamma-ray-detected sources were also interpreted with a spine–layer model and a proton synchrotron model. The three models provide a good description of the SEDs. However, the resulting parameters differ substantially in the three scenarios, in particular the magnetization parameter. This work presents the first mini catalog of VHE gamma-ray and multiwavelength observations of EHBLs.