Observations of Mkn 421 in 2004 with H.E.S.S. at large zenith angles

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

doi:10.1051/0004-6361:20053050

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Observations of Mkn 421 in 2004 with H.E.S.S. at large zenith angles

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Observations of Mkn 421 in 2004 with H.E.S.S. at large zenith angles

F. Aharonian, A. G. Akhperjanian, K.-M. Aye, A. R. Bazer-Bachi, M. Beilicke, W. Benbow, D. Berge, P. Berghaus, K. Bernlöhr, C. Boisson, …

Astronomy & Astrophysics - A&A, Vol.437, pp.95-99

2005

DOI: https://doi.org/10.1051/0004-6361:20053050

Abstract

galaxies: individual: Mkn 421

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 (H.E.S.S.) in Namibia. The observations were carried out at zenith angles of 60$^\circ$--65$^\circ$, which result in an average energy threshold of 1.5 TeV and a collection area reaching 2 km$^2$ 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 hour. The time averaged energy spectrum is curved and is well described by a power-law with a photon index $\egamm$ and an exponential cutoff at $\ecut$ 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 $\approx 300$ GeV) indicate smaller relative variability amplitudes than seen above 2 TeV during high flux state observed in April 2004.

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Title: Observations of Mkn 421 in 2004 with H.E.S.S. at large zenith angles
Creators - without role: F. Aharonian - Max Planck Society
A. G. Akhperjanian
K.-M. Aye - Durham University
A. R. Bazer-Bachi
M. Beilicke - Universität Hamburg
W. Benbow - Max Planck Society
D. Berge - Max Planck Society
P. Berghaus - Collège de France
K. Bernlöhr - Humboldt-Universität zu Berlin
C. Boisson - Centre de Gestion Scientifique
O. Bolz - Max Planck Innovation
I. Braun - Max Planck Innovation
F. Breitling - Humboldt-Universität zu Berlin
A. M. Brown
J. Bussons Gordo - Laboratoire de Physique Théorique
P. M. Chadwick
L.-M. Chounet - Laboratoire Leprince-Ringuet
R. Cornils - Universität Hamburg
L. Costamante - Centre de Gestion Scientifique
B. Degrange - Laboratoire d'Informatique de l'École Polytechnique
A. Djannati-Ataï - AstroParticule et Cosmologie
L. O'C. Drury
G. Dubus - Laboratoire d'Informatique de l'École Polytechnique
D. Emmanoulopoulos
P. Espigat - Collège de France
F. Feinstein - Université de Montpellier
P. Fleury - Laboratoire d'Informatique de l'École Polytechnique
G. Fontaine - Laboratoire d'Informatique de l'École Polytechnique
Y. Fuchs - Université Joseph Fourier
S. Funk - Max Planck Society
Y.A. Gallant - Université de Montpellier
B. Giebels - Laboratoire d'Informatique de l'École Polytechnique
S. Gillessen - Max Planck Society
J. F. Glicenstein
P. Goret - DSM (Netherlands)
C. Hadjichristidis - Durham University
M. Hauser - Commissariat à l'Énergie Atomique et aux Énergies Alternatives
G. Heinzelmann - Universität Hamburg
G. Henri - Université Joseph Fourier
G. Hermann - Max Planck Innovation
J. A. Hinton
W. Hofmann - Max Planck Society
M. Holleran - North-West University
D. Horns - Max Planck Society
O. C. de Jager
B. Khélifi - Max Planck Society
Nu. Komin - Humboldt-Universität zu Berlin
A. Konopelko - Max Planck Society
I. J. Latham
R. Le Gallou - Durham University
A. Lemière - Collège de France
M. Lemoine - Laboratoire d'Informatique de l'École Polytechnique
N. Leroy - Laboratoire d'Informatique de l'École Polytechnique
T. Lohse - Humboldt-Universität zu Berlin
A. Marcowith - Centre de Gestion Scientifique
C. Masterson - Max Planck Innovation
T. J. L. Mccomb
M. de Naurois - Centre de Gestion Scientifique
S. J. Nolan
A. Noutsos - Durham University
K. J. Orford
J. L. Osborne
M. Ouchrif - Centre de Gestion Scientifique
M. Panter - Max Planck Innovation
G. Pelletier - Université Joseph Fourier
S. Pita - Collège de France
G. Pühlhofer - Max Planck Innovation
M. Punch - Collège de France
B. C. Raubenheimer
M. Raue - Universität Hamburg
J. Raux - Centre de Gestion Scientifique
S. M. Rayner
I. Redondo - Laboratoire d'Informatique de l'École Polytechnique
A. Reimer - Ruhr University Bochum
O. Reimer - Ruhr University Bochum
J. Ripken - Universität Hamburg
L. Rob - Charles University
L. Rolland - Centre de Gestion Scientifique
G. Rowell - Max Planck Innovation
V. Sahakian - A. Alikhanyan National Laboratory
L. Saugé - Université Joseph Fourier
S. Schlenker - Humboldt-Universität zu Berlin
R. Schlickeiser - Ruhr University Bochum
C. Schuster - Ruhr University Bochum
U. Schwanke - Humboldt-Universität zu Berlin
M. Siewert - Ruhr University Bochum
H. Sol - Centre de Gestion Scientifique
R. Steenkamp - University of Namibia
C. Stegmann - Humboldt-Universität zu Berlin
J.-P. Tavernet - Laboratoire de Physique Nucléaire et de Hautes Énergies
R. Terrier - Collège de France
C.G. Théoret - Collège de France
M. Tluczykont - Laboratoire d'Informatique de l'École Polytechnique
G. Vasileiadis - Université de Montpellier
C. Venter - North-West University
P. Vincent - Centre de Gestion Scientifique
H. J. Völk
S. J. Wagner
Publication Details: Astronomy & Astrophysics - A&A, Vol.437, pp.95-99
Identifiers: 9935001309311
Academic Unit: Université de Montpellier
Language: English
Resource Type: Journal article
Local Fields: in2p3-00024439