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.