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.; Berge, D.; Berghaus, P.; Bernlöhr, K.; Bolz, O.; Boisson, C:; Glicenstein, J.F.; Breitling, F.; Brown, A. M.; Bussons Gordo, J.; Chadwick, P. M.; Braun, I.; Chounet, L.-M.; Cornils, R.; Costamante, L.; Degrange, B.; Djannati-Atai, A.; Drury, L.O'C.; Emmanoulopoulos, D.; Espigat, P.; Feinstein, F.; Fleury, P.; Fontaine, G.; Funk, S.; Gallant, Y. A.; Giebels, B.; Gillessen, S.; Goret, P.; Dubus, G.; Hadjichristidis, C.; Hauser, M.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Holleran, M.; Horns, D.; de Jager, O. C.; Khélifi, B.; Komin, N.; Konopelko, A.; Latham, I. J.; Le Gallou, R.; Lemoine-Goumard, M.; Lemière, A.; Leroy, N.; Lohse, T.; Marcowith, A.; Masterson, C.; McComb, T. J. L.; de Naurois, M.; Nolan, S. J.; Noutsos, A.; Orford, K. J.; Osborne, J. L.; Ouchrif, M.; Panter, M.; Pelletier, G.; Pita, S.; Fuchs, Y.; Pühlhofer, G.; Punch, M.; Raubenheimer, B. C.; Raue, M.; Raux, J.; Rayner, S. M.; Redondo, I.; Reimer, A.; Reimer, O.; Ripken, J.; Terrier, R.; Rob, L.; Rolland, L.; Rowell, G.; Sahakian, V.; Saugé, L.; Schlenker, S.; Schlickeiser, R.; Schuster, C.; Schwanke, U.; Siewert, M.; Sol, H.; Steenkamp, R.; Stegmann, C.; Tavernet, J.-P-; Théoret, C. G.; Tluczykont, M.; Venter, C.; Vasileiadis, G.; Vincent, P.; Völk, H. J.; Wagner, S. J.; Martineau-Huynh, O.

doi:10.1051/0004-6361:20053050

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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: https://hdl.handle.net/11858/00-001M-0000-0011-88A6-8 Version Permalink: https://hdl.handle.net/11858/00-001M-0000-0011-88A7-6

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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 ± 0.1_stat ± 0.3_sys and an exponential cutoff at Ε_c= 3.1(+ 0.5 - 0.4)_stat ± 0.9_sys 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: Date issued: 2005-07-01

Publication Status: Issued

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Identifiers: eDoc: 236886
DOI: 10.1051/0004-6361:20053050

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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: -