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Astronomy and Astrophysics 473 (2007) L25-L28
Discovery of VHE gamma-rays from the distant BL Lacertae 1ES 0347-121
F. Aharonian, A. G. Akhperjanian, U. Barres De Almeida, A.R. Bazer-Bachi1, B. Behera, M. Beilicke, W. Benbow, K. Bernlöhr, C. Boisson2, O. Bolz, V. Borrel1, I. Braun, E. Brion3, A. M. Brown, R. Bühler, T. Bulik4, I. Büsching, T. Boutelier5, S. Carrigan, P. M. Chadwick, L.-M. Chounet6, A. C. Clapson, G. Coignet7, R. Cornils, L. Costamante, M. Dalton, B. Degrange6, H. J. Dickinson, A. Djannati-Ataï8, W. Domainko, L. O'C. Drury, F. Dubois7, G. Dubus5, J. Dyks, K. Egberts, D. Emmanoulopoulos, P. Espigat8, C. Farnier9, F. Feinstein9, A. Fiasson9, A. Förster, G. Fontaine6, Seb. Funk, M. Füßling, Y.A. Gallant9, B. Giebels6, J. F. Glicenstein3, B. Glück, P. Goret3, C. Hadjichristidis, D. Hauser, M. Hauser, G. Heinzelmann, G. Henri5, G. Hermann, J. A. Hinton, A. Hoffmann, W. Hofmann, M. Holleran, S. Hoppe, D. Horns, A. Jacholkowska9, O. C. de Jager10, I. Jung, K. Katarzynski, E. Kendziorra, M. Kerschhaggl, B. Khélifi6, D. Keogh, Nu. Komin9, K. Kosack, G. Lamanna7, I. J. Latham, A. Lemière8, M. Lemoine-Goumard6, J.-P. Lenain2, T. Lohse, J. M. Martin2, O. Martineau-Huynh11, A. Marcowith9, C. Masterson, D. Maurin11, G. Maurin8, T. J. L. McComb, R. Moderski, E. Moulin3, M. De Naurois11, D. Nedbal, S. J. Nolan, S. Ohm, J.-P. Olive1, E. de Oña Wilhelmi8, K. J. Orford, J. L. Osborne, M. Ostrowski, M. Panter, G. Pedaletti, G. Pelletier5, P.-O. Petrucci5, S. Pita8, G. Pühlhofer, M. Punch8, S. Ranchon7, B. C. Raubenheimer, M. Raue, S. M. Rayner, M. Renaud12, J. Ripken, L. Rob, L. Rolland3, S. Rosier-Lees7, G. Rowell, B. Rudak, J. Ruppel, V. Sahakian13, A. Santangelo, R. Schlickeiser14, F. Schöck, R. Schröder, U. Schwanke, S. Schwarzburg, S. Schwemmer, A. Shalchi, H. Sol2, D. Spangler, L. Stawarz, R. Steenkamp, C. Stegmann, G. Superina6, P. H. Tam, J.-P. Tavernet11, R. Terrier8, C. Van Eldik, G. Vasileiadis9, C. Venter, J.P. Vialle7, P. Vincent11, M. Vivier3, H. J. Völk, F. Volpe6, S. J. Wagner, M. Ward, A. A. Zdziarski, A. Zech2
HESS Collaboration(s)

Aims.Our aim is to study the production mechanism for very-high-energy (VHE; >100 GeV) ?-rays in distant active galactic nuclei (AGN) and use the observed VHE spectrum to derive limits on the Extragalactic Background Light (EBL). We also want to determine physical quantities through the modeling of the object's broad-band spectral energy distribution (SED). Methods: VHE observations (~25 h live time) of the BL Lac 1ES 0347-121 (redshift z = 0.188) were conducted with the High Energy Stereoscopic System (HESS) between August and December 2006. Contemporaneous X-ray and UV/optical observations from the SWIFT satellite are used to interpret the SED of the source in terms of a synchrotron self Compton (SSC) model. Results: An excess of 327 events, corresponding to a statistical significance of 10.1 standard deviations, is detected from 1ES 0347-121. Its photon spectrum, ranging from ~250 GeV to ~3 TeV, is well described by a power law with a photon index of ? = 3.10 ± 0.23stat ± 0.10sys. The integral flux above 250 GeV corresponds to ~2% of the flux of the Crab Nebula above the same threshold. No VHE flux variability is detected within the data set. Conclusions: Constraints on the EBL density at optical to near-infrared wavelengths derived from the photon spectrum of 1ES 0347-121 are close to the strongest limits derived previously. The strong EBL limits confirm earlier findings, that the EBL density in the near-infrared is close to the lower limits from source counts. This implies that the universe is more transparent to VHE ?-rays than previously believed. An SSC model provides a reasonable description of the contemporaneous SED. Affiliations are only available in electronic form at http://www.aanda.org
1 :  CESR - Centre d'étude spatiale des rayonnements
2 :  LUTH - Laboratoire Univers et Théories
3 :  DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
4 :  CAMK - Copernicus Astrophysical Center
5 :  LAOG - Laboratoire d'Astrophysique de Grenoble
6 :  LLR - Laboratoire Leprince-Ringuet
7 :  LAPP - Laboratoire d'Annecy le Vieux de Physique des Particules
8 :  APC - UMR 7164 - AstroParticule et Cosmologie
9 :  LPTA - Laboratoire de Physique Théorique et Astroparticules
10 :  Unit for Space Physics, North-West University, South-Africa
11 :  LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
12 :  MPI-K - Max-Planck-Institut fuer Kernphysik, Heidelberg
13 :  LAL - Laboratoire de l'Accélérateur Linéaire
14 :  Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique
galaxies: BL Lacertae objects: individual: 1ES0347-121 – gamma rays: observations – cosmology: diffuse radiation – galaxies: BL Lacertae objects: general – galaxies: active
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