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

MPS-Authors

/persons/resource/persons30244

Aharonian, F.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30247

Akhperjanian, A. G.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30290

Beilicke, M.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30293

Benbow, W.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30296

Berge, D.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30300

Bernlöhr, K.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30322

Bolz, O.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30521

Glicenstein, J.F.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30333

Braun, I.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30380

Cornils, R.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30382

Costamante, L.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30414

Djannati-Atai, A.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Feinstein, F.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30497

Funk, S.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Gallant, Y. A.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Gillessen, S.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Dubus, G.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Hermann, G.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30597

Hinton, J. A.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30605

Hofmann, W.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Horns, D.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Khélifi, B.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Konopelko, A.
Prof. Heinrich J. Völk, Emeriti, MPI for Nuclear Physics, Max Planck Society;

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Masterson, C.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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de Naurois, M.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30865

Orford, K. J.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30869

Osborne, J. L.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30878

Panter, M.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30914

Pühlhofer, G.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30923

Raue, M.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30959

Rowell, G.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons30976

Saugé, L.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

/persons/resource/persons31135

Vasileiadis, G.
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

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Völk, H. J.
Prof. Heinrich J. Völk, Emeriti, MPI for Nuclear Physics, Max Planck Society;

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Citation

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.

Cite as: https://hdl.handle.net/11858/00-001M-0000-0011-88A6-8

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.