New Hard-TeV Extreme Blazars Detected with the MAGIC Telescopes

Acciari V. A.; Ansoldi S.; Antonelli L. A.; Engels A. A.; Asano K.; Baack D.; Babic A.; Banerjee B.; De Almeida U. B.; Barrio J. A.; Gonzalez J. B.; 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.; 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. D.; Dazzi F.; Angelis A. D.; Lotto B. D.; Delfino M.; Delgado J.; Depaoli D.; Pierro F. D.; Venere L. D.; Souto Espieira E. D.; Prester D. D.; Donini A.; Dorner D.; Doro M.; Elsaesser D.; Ramazani V. F.; Fattorini A.; Ferrara G.; Fidalgo D.; Foffano L.; Fonseca M. V.; Font L.; Fruck C.; Fukami S.; Lopez R. J. G.; Garczarczyk M.; Gasparyan S.; Gaug M.; Giglietto N.; Giordano F.; Godinovic N.; Green D.; Guberman D.; Hadasch D.; Hahn A.; Herrera J.; Hoang J.; Hrupec D.; Hutten 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.; Lopez M.; Lopez-Coto R.; Lopez-Oramas A.; Loporchio S.; De Oliveira Fraga B. M.; Maggio C.; Majumdar P.; Makariev M.; Mallamaci M.; Maneva G.; Manganaro M.; Mannheim K.; Maraschi L.; Mariotti M.; Martinez M.; Mazin D.; Micanovic 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.; Nogues L.; Nozaki S.; Paiano S.; Palatiello M.; Paneque D.; Paoletti R.; Paredes J. M.; Peil P.; Peresano M.; Persic M.; Moroni P. G. P.; Prandini E.; Puljak I.; Rhode W.; Ribo M.; Rico J.; Righi C.; Rugliancich A.; Saha L.; Sahakyan N.; Saito T.; Sakurai S.; Satalecka K.; Schmidt K.; Schweizer T.; Sitarek J.; Snidaric I.; Sobczynska D.; Somero A.; Stamerra A.; Strom D.; Strzys M.; Suda Y.; Suric T.; Takahashi M.; Tavecchio F.; Temnikov P.; Terzic T.; Teshima M.; Torres-Alb N.; Tosti L.; Vagelli V.; Scherpenberg J. V.; Vanzo G.; Acosta M. V.; Vigorito C. F.; Vitale V.; Vovk I.; Will M.; Zaric D.; Arcaro C.; Carosi A.; D'Ammando F.; Tombesi F.; Lohfink A.

doi:10.3847/1538-4365/ab5b98

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.