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VHE gamma-ray discovery and multiwavelength study of the blazar 1ES 2322-409

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posted on 2019-06-21, 09:11 authored by H Abdalla, F Aharonian, FA Benkhali, EO Anguner, M Arakawa, C Arcaro, C Armand, M Arrieta, M Backes, M Barnard, Y Becherini, JB Tjus, D Berge, S Bernhard, K Bernloehr, R Blackwell, M Bottcher, C Boisson, J Bolmont, S Bonnefoy, P Bordas, J Bregeon, F Brun, P Brun, M Bryan, M Buechele, T Bulik, T Bylund, M Capasso, S Caroff, A Carosi, S Casanova, M Cerruti, N Chakraborty, S Chandra, RCG Chaves, A Chen, S Colafrancesco, B Condon, ID Davids, C Dei, J Devin, P deWilt, L Dirson, A Djannati-Atai, A Dmytriiev, A Donath, LOC Drury, J Dyks, K Egberts, G Emery, J-P Ernenwein, S Eschbach, S Fegan, A Fiasson, G Fontaine, S Funk, M Fuessling, S Gabici, YA Gallant, T Garrigoux, F Gate, G Giavitto, D Glawion, JF Glicenstein, D Gottschall, M-H Grondin, J Hahn, M Haupt, G Heinzelmann, G Henri, G Hermann, JA Hinton, W Hofmann, C Hoischen, TL Holch, M Holler, D Horns, D Huber, H Iwasaki, A Jacholkowska, M Jamrozy, D Jankowsky, F Jankowsky, L Jouvin, I Jung-Richardt, MA Kastendieck, K Katarzynski, M Katsuragawa, U Katz, D Kerszberg, D Khangulyan, B Khelifi, J King, S Klepser, W Kluzniak, N Komin, K Kosack, S Krakau, M Kraus, RR Kruger, G Lamanna, J Lau, J Lefaucheur, A Lemiere, M Lemoine-Goumard, J-P Lenain, E Leser, T Lohse, M Lorentz, R Lopez-Coto, I Lypova, D Malyshev, V Marandon, A Marcowith, C Mariaud, G Marti-Devesa, R Marx, G Maurin, PJ Meintjes, AMW Mitche, R Moderski, M Mohamed, L Mohrmann, E Moulin, T Murach, S Nakashima, M de Naurois, H Ndiyavala, F Niederwanger, J Niemiec, L Oakes, P O'Brien, H Odaka, S Ohm, M Ostrowski, I Oya, M Padovani, M Panter, RD Parsons, C Perennes, P-O Petrucci, B Peyaud, Q Piel, S Pita, V Poireau, AP Noel, DA Prokhorov, H Prokoph, G Puehlhofer, M Punch, A Quirrenbach, S Raab, R Rauth, A Reimer, O Reimer, M Renaud, F Rieger, L Rinchiuso, C Romoli, G Rowell, B Rudak, E Ruiz-Velasco, V Sahakian, S Saito, DA Sanchez, A Santangelo, M Sasaki, R Schlickeiser, F Schussler, A Schulz, U Schwanke, S Schwemmer, M Seglar-Arroyo, M Senniappan, AS Seyffert, N Shafi, I Shilon, K Shiningayamwe, R Simoni, A Sinha, H Sol, F Spanier, A Specovius, M Spir-Jacob, L Stawarz, R Steenkamp, C Stegmann, C Steppa, I Sushch, T Takahashi, J-P Tavernet, T Tavernier, AM Taylor, R Terrier, L Tibaldo, D Tiziani, M Tluczykont, C Trichard, M Tsirou, N Tsuji, R Tuffs, Y Uchiyama, DJ van der Walt, C van Eldik, C van Rensburg, B van Soelen, G Vasileiadis, J Veh, C Venter, A Viana, P Vincent, J Vink, F Voisin, HJ Voelk, T Vuillaume, Z Wadiasingh, SJ Wagner, P Wagner, RM Wagner, R White, A Wierzcholska, A Woernlein, R Yang, D Zaborov, M Zacharias, R Zanin, AA Zdziarski, A Zech, F Zefi, A Ziegler, J Zorn, N Zywucka
A hotspot at a position compatible with the BL Lac object 1ES 2322−409 was serendipitously detected with H.E.S.S. during observations performed in 2004 and 2006 on the blazar PKS 2316−423. Additional data on 1ES 2322−409 were taken in 2011 and 2012, leading to a total live-time of 22.3 h. Point-like very-high-energy (VHE; E > 100 GeV) γ -ray emission is detected from a source centred on the 1ES 2322−409 position, with an excess of 116.7 events at a significance of 6.0σ. The average VHE γ -ray spectrum is well described with a power law with a photon index = 3.40 ± 0.66stat ± 0.20sys and an integral flux (E > 200 GeV) = (3.11 ± 0.71stat ± 0.62sys) × 10−12 cm−2 s−1, which corresponds to 1.1 per cent of the Crab nebula flux above 200 GeV. Multiwavelength data obtained with Fermi LAT, Swift XRT and UVOT, RXTE PCA, ATOM, and additional data from WISE, GROND, and Catalina are also used to characterize the broad-band non-thermal emission of 1ES 2322−409. The multiwavelength behaviour indicates day-scale variability. Swift UVOT and XRT data show strong variability at longer scales. A spectral energy distribution (SED) is built from contemporaneous observations obtained around a high state identified in Swift data. A modelling of the SED is performed with a stationary homogeneous one-zone synchrotronself-Compton leptonic model. The redshift of the source being unknown, two plausible values were tested for the modelling. A systematic scan of the model parameters space is performed, resulting in a well-constrained combination of values providing a good description of the broad-band behaviour of 1ES 2322−409.


The support of the Namibian authorities and of the University of Namibia in facilitating the construction and operation of H.E.S.S. is gratefully acknowledged, as is the support by the German Ministry for Education and Research (BMBF), the Max Planck Society, the German Research Foundation (DFG), the Alexander von Humboldt Foundation, the Deutsche Forschungsgemeinschaft, the French Ministry for Research, the CNRS-IN2P3 and the Astroparticle Interdisciplinary Programme of the CNRS, the U.K. Science and Technology Facilities Council (STFC), the IPNP of the Charles University, the Czech Science Foundation, the Polish National Science Centre, the South African Department of Science and Technology and National Research Foundation, the University of Namibia, the National Commission on Research, Science & Technology of Namibia (NCRST), the Innsbruck University, the Austrian Science Fund (FWF), and the Austrian Federal Ministry for Science, Research and Economy, the University of Adelaide and the Australian Research Council, the Japan Society for the Promotion of Science and by the University of Amsterdam. We appreciate the excellent work of the technical support staff in Berlin, Durham, Hamburg, Heidelberg, Palaiseau, Paris, Saclay, and in Namibia in the construction and operation of the equipment. This work benefited from services provided by the H.E.S.S. Virtual Organisation, supported by the national resource providers of the EGI Federation. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory



Monthly Notices of the Royal Astronomical Society, 2019, 482 (3), pp. 3011-3022 (12)

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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