EDP Sciences
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Volume 425, Number 1, October I 2004
Page(s) L13 - L17
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200400055

A&A 425, L13-L17 (2004)
DOI: 10.1051/0004-6361:200400055


Very high energy gamma rays from the direction of Sagittarius A *

F. Aharonian1, A. G. Akhperjanian2, K.-M. Aye3, A. R. Bazer-Bachi4, M. Beilicke5, W. Benbow1, D. Berge1, P. Berghaus6, K. Bernlöhr1, 7, O. Bolz1, C. Boisson8, C. Borgmeier7, F. Breitling7, A. M. Brown3, J. Bussons Gordo9, P. M. Chadwick3, V. R. Chitnis10, 11, L.-M. Chounet12, R. Cornils5, L. Costamante1, 11, B. Degrange12, A. Djannati-Ataï6, L. O'C. Drury13, T. Ergin7, P. Espigat6, F. Feinstein9, P. Fleury12, G. Fontaine12, S. Funk1, Y. Gallant9, B. Giebels12, S. Gillessen1, P. Goret14, J. Guy10, C. Hadjichristidis3, M. Hauser15, G. Heinzelmann5, G. Henri16, G. Hermann1, J. A. Hinton1, W. Hofmann1, M. Holleran17, D. Horns1, O. C. de Jager17, I. Jung1, 15, B. Khélifi1, Nu. Komin7, A. Konopelko1, 7, I. J. Latham3, R. Le Gallou3, M. Lemoine12, A. Lemière6, N. Leroy12, T. Lohse7, A. Marcowith4, C. Masterson1, 11, T. J. L. McComb3, M. de Naurois10, S. J. Nolan3, A. Noutsos3, K. J. Orford3, J. L. Osborne3, M. Ouchrif10, 11, M. Panter1, G. Pelletier16, S. Pita6, M. Pohl18, G. Pühlhofer1, 15, M. Punch6, B. C. Raubenheimer17, M. Raue5, J. Raux10, S. M. Rayner3, I. Redondo12, 11, A. Reimer18, O. Reimer18, J. Ripken5, M. Rivoal10, L. Rob19, L. Rolland10, G. Rowell1, V. Sahakian2, L. Saugé16, S. Schlenker7, R. Schlickeiser18, C. Schuster18, U. Schwanke7, M. Siewert18, H. Sol8, R. Steenkamp20, C. Stegmann7, J.-P. Tavernet10, C. G. Théoret6, M. Tluczykont12, 11, D. J. van der Walt17, G. Vasileiadis9, P. Vincent10, B. Visser17, H. J. Völk1 and S. J. Wagner15

1  Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany
    e-mail: Jim.Hinton@mpi-hd.mpg.de
2  Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036 Yerevan, Armenia
3  University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK
4  Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, 9 Av. du Colonel Roche, BP 4346, 31029 Toulouse Cedex 4, France
5  Universität Hamburg, Inst. für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
6  Physique Corpusculaire et Cosmologie, IN2P3/CNRS, Collège de France, 11 place Marcelin Berthelot, 75231 Paris Cedex 05, France
7  Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
8  LUTH, UMR 8102 du CNRS, Observatoire de Paris, Section de Meudon, 92195 Meudon Cedex, France
9  Groupe d'Astroparticules de Montpellier, IN2P3/CNRS, Université Montpellier II, CC85, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
10  Laboratoire de Physique Nucléaire et de Hautes Énergies, IN2P3/CNRS, Universités Paris VI & VII, 4 place Jussieu, 75231 Paris Cedex 05, France
11  European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
12  Laboratoire Leprince-Ringuet, IN2P3/CNRS, École Polytechnique, 91128 Palaiseau, France
13  Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland
14  Service d'Astrophysique, DAPNIA/DSM/CEA, CE Saclay, 91191 Gif-sur-Yvette, France
15  Landessternwarte, Königstuhl, 69117 Heidelberg, Germany
16  Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France
17  Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa
18  Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
19  Institute of Particle and Nuclear Physics, Charles University, V Holesovickach 2, 180 00 Prague 8, Czech Republic
20  University of Namibia, Private Bag 13301, Windhoek, Namibia

(Received 29 June 2004 / Accepted 12 August 2004)

We report the detection of a point-like source of very high energy (VHE) $\gamma$-rays coincident within  1' of Sgr A *, obtained with the HESS array of Cherenkov telescopes. The $\gamma$-rays exhibit a power-law energy spectrum with a spectral index of $-2.2 \pm 0.09
\pm 0.15$ and a flux above the 165 GeV threshold of $(1.82 \pm 0.22) \times 10^{-7}$ m -2 s -1. The measured flux and spectrum differ substantially from recent results reported in particular by the CANGAROO collaboration.

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