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  Observations of Mkn 421 in 2004 with HESS at large zenith angles

Aharonian, F., Akhperjanian, A. G., Aye, K.-M., Bazer-Bachi, A. R., Beilicke, M., Benbow, W., et al. (2005). Observations of Mkn 421 in 2004 with HESS at large zenith angles. Astronomy & Astrophysics, 437(1), 95-99. doi:10.1051/0004-6361:20053050.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0011-88A6-8 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0011-88A7-6
Genre: Journal Article

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 Creators:
Aharonian, F.1, Author              
Akhperjanian, A. G.1, Author              
Aye, K.-M.2, Author
Bazer-Bachi, A. R.2, Author
Beilicke, M.1, Author              
Benbow, W.1, Author              
Berge, D.1, Author              
Berghaus, P.2, Author
Bernlöhr, K.1, Author              
Bolz, O.1, Author              
Boisson, C:2, Author
Glicenstein, J.F.1, Author              
Breitling, F.2, Author
Brown, A. M.2, Author
Bussons Gordo, J.2, Author
Chadwick, P. M.2, Author
Braun, I.1, Author              
Chounet, L.-M.2, Author
Cornils, R.1, Author              
Costamante, L.1, Author              
Degrange, B.2, AuthorDjannati-Atai, A.1, Author              Drury, L.O'C.2, AuthorEmmanoulopoulos, D.2, AuthorEspigat, P.2, AuthorFeinstein, F.1, Author              Fleury, P.2, AuthorFontaine, G.2, AuthorFunk, S.1, Author              Gallant, Y. A.1, Author              Giebels, B.2, AuthorGillessen, S.1, Author              Goret, P.2, AuthorDubus, G.1, Author              Hadjichristidis, C.2, AuthorHauser, M.2, AuthorHeinzelmann, G.2, AuthorHenri, G.2, AuthorHermann, G.1, Author              Hinton, J. A.1, Author              Hofmann, W.1, Author              Holleran, M.2, AuthorHorns, D.1, Author              de Jager, O. C.2, AuthorKhélifi, B.1, Author              Komin, N.2, AuthorKonopelko, A.3, Author              Latham, I. J.2, AuthorLe Gallou, R.2, AuthorLemoine-Goumard, M.2, AuthorLemière, A.2, AuthorLeroy, N.2, AuthorLohse, T.2, AuthorMarcowith, A.2, AuthorMasterson, C.1, Author              McComb, T. J. L.2, Authorde Naurois, M.1, Author              Nolan, S. J.2, AuthorNoutsos, A.2, AuthorOrford, K. J.1, Author              Osborne, J. L.1, Author              Ouchrif, M.2, AuthorPanter, M.1, Author              Pelletier, G.2, AuthorPita, S.2, AuthorFuchs, Y.2, AuthorPühlhofer, G.1, Author              Punch, M.2, AuthorRaubenheimer, B. C.2, AuthorRaue, M.1, Author              Raux, J.2, AuthorRayner, S. M.2, AuthorRedondo, I.2, AuthorReimer, A.2, AuthorReimer, O.2, AuthorRipken, J.2, AuthorTerrier, R.2, AuthorRob, L.2, AuthorRolland, L.2, AuthorRowell, G.1, Author              Sahakian, V.2, AuthorSaugé, L.1, Author              Schlenker, S.2, AuthorSchlickeiser, R.2, AuthorSchuster, C.2, AuthorSchwanke, U.2, AuthorSiewert, M.2, AuthorSol, H.2, AuthorSteenkamp, R.2, AuthorStegmann, C.2, AuthorTavernet, J.-P-2, AuthorThéoret, C. G.2, AuthorTluczykont, M.2, AuthorVenter, C.2, AuthorVasileiadis, G.1, Author              Vincent, P.2, AuthorVölk, H. J.3, Author              Wagner, S. J.2, AuthorMartineau-Huynh, O.2, Author more..
Affiliations:
1Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society, ou_904550              
2Yerevan Physics Institute, Armenia University of Durham, Department of Physics, UK Centre d'Etudes Spatiales des Rayonnements, CNRS/UPS Toulouse, France Universität Hamburg, Institut für Experimentalphysik, Germany Physique Corpusculaire et Cosmologie, IN2P3/CNRS, Collège de France, Paris, France Institut für Physik, Humboldt-Universität zu Berlin, Germany LUTH, UMR 8102 du CNRS, Observatoire de Paris, Section de Meudon, France Groupe d'astroparticules de Montpellier, IN2P3/CNRS, Université Montpellier II, France Laboratoire de Physique Nucléaire et de Hautes Energies, IN2P3/CNRS, Universités Paris VI & VII, Jussieu, France European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG Laboratoire Leprince-Ringuet, IN2P3/CNRS, Ecole Polytechnique, Palaiseau, France Dublin Institute for Advanced Studies, Ireland Service d'Astrophysique. DAPNIA/DSM/CEA, CE Saclay, Gif-sur-Yvette, France Landessternwarte, Königstuhl, Heidelberg, Germany Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, France Unit for Space Physics, North-West University, Potchefstroom, South Africa Institut für theoretische Physik, Lehrstuhl IV, Ruhr-Universität Bochum, Germany Institute of Particle and Nuclear Physics, Charles University, Prague, Czech Republic University of Namibia, Windhoek, Namibia, ou_persistent22              
3Prof. Heinrich J. Völk, Emeriti, MPI for Nuclear Physics, Max Planck Society, ou_907548              

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Free keywords: galaxies: individual: Mkn 421
 Abstract: Mkn 421 was observed during a high flux state for nine nights in April and May 2004 with the fully operational High Energy Stereoscopic System (HESS) in Namibia. The observations were carried out at zenith angles of 60°-65°, which result in an average energy threshold of 1.5 TeV and a collection area reaching 2 km2 at 10 TeV. Roughly 7000 photons from Mkn 421 were accumulated with an average gamma-ray rate of 8 photons/min. The overall significance of the detection exceeds 100 standard deviations. The light-curve of integrated fluxes above 2 TeV shows changes of the diurnal flux up to a factor of 4.3. For nights of high flux, intra-night variability is detected with a decay time of less than 1 h. The time averaged energy spectrum is curved and is well described by a power-law with a photon index Γ = 2.1 ± 0.1stat ± 0.3sys and an exponential cutoff at Εc= 3.1(+ 0.5 - 0.4)stat ± 0.9sys TeV and an average integral flux above 2 TeV of 3 Crab flux units. Significant variations of the spectral shape are detected with a spectral hardening as the flux increases. Contemporaneous multi-wavelength observations at lower energies (X-rays and gamma-rays above 300 GeV) indicate smaller relative variability amplitudes than seen above 2 TeV during high flux state observed in April 2004.

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Language(s): eng - English
 Dates: 2005-07-01
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: -
 Identifiers: eDoc: 236886
DOI: 10.1051/0004-6361:20053050
 Degree: -

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Title: Astronomy & Astrophysics
  Alternative Title : A&A
Source Genre: Journal
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Pages: - Volume / Issue: 437 (1) Sequence Number: - Start / End Page: 95 - 99 Identifier: -