EDP Sciences
Free access
Issue A&A
Volume 442, Number 1, October IV 2005
Page(s) 1 - 10
Section Astrophysical processes
DOI http://dx.doi.org/10.1051/0004-6361:20052983



A&A 442, 1-10 (2005)
DOI: 10.1051/0004-6361:20052983

Discovery of the binary pulsar PSR B1259-63 in very-high-energy gamma rays around periastron with HESS

F. Aharonian1, A. G. Akhperjanian2, K.-M. Aye3, A. R. Bazer-Bachi4, M. Beilicke5, W. Benbow1, D. Berge1, P. Berghaus6, K. Bernlöhr1, 7, C. Boisson8, O. Bolz1, I. Braun1, F. Breitling7, A. M. Brown3, J. Bussons Gordo9, P. M. Chadwick3, L.-M. Chounet10, R. Cornils5, L. Costamante1, 11, B. Degrange10, A. Djannati-Ataï6, L. O'C. Drury12, G. Dubus10, D. Emmanoulopoulos13, P. Espigat6, F. Feinstein9, P. Fleury10, G. Fontaine10, Y. Fuchs14, S. Funk1, Y. A. Gallant9, B. Giebels10, S. Gillessen1, J. F. Glicenstein15, P. Goret15, C. Hadjichristidis3, M. Hauser13, G. Heinzelmann5, G. Henri14, G. Hermann1, J. A. Hinton1, W. Hofmann1, M. Holleran16, D. Horns1, O. C. de Jager16, S. Johnston17, B. Khélifi1, J. G. Kirk1, Nu. Komin7, A. Konopelko1, 7, I. J. Latham3, R. Le Gallou3, A. Lemière6, M. Lemoine-Goumard10, N. Leroy10, O. Martineau-Huynh18, T. Lohse7, A. Marcowith4, C. Masterson1, 11, T. J. L. McComb3, M. de Naurois18, S. J. Nolan3, A. Noutsos3, K. J. Orford3, J. L. Osborne3, M. Ouchrif18, 11, M. Panter1, G. Pelletier14, S. Pita6, G. Pühlhofer1, 13, M. Punch6, B. C. Raubenheimer16, M. Raue5, J. Raux18, S. M. Rayner3, I. Redondo10, 11, A. Reimer19, O. Reimer19, J. Ripken5, L. Rob20, L. Rolland18, G. Rowell1, V. Sahakian2, L. Saugé14, S. Schlenker7, R. Schlickeiser19, C. Schuster19, U. Schwanke7, M. Siewert19, O. Skjæraasen21, H. Sol8, R. Steenkamp22, C. Stegmann7, J.-P. Tavernet18, R. Terrier6, C. G. Théoret6, M. Tluczykont10, 11, G. Vasileiadis9, C. Venter16, P. Vincent18, H. J. Völk1 and S. J. Wagner13

1  Max-Planck-Institut für Kernphysik, Heidelberg, Germany
2  Yerevan Physics Institute, Yerevan, Armenia
3  University of Durham, Department of Physics, Durham, UK
4  Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, Toulouse, France
5  Universität Hamburg, Institut für Experimentalphysik, Hamburg, Germany
6  APC, Paris, France
7  Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
    e-mail: schlenk@physik.hu-berlin.de
8  LUTH, UMR 8102 du CNRS, Observatoire de Paris, Meudon, France
9  Groupe d'Astroparticules de Montpellier, IN2P3/CNRS, Université Montpellier II, Montpellier, France
10  Laboratoire Leprince-Ringuet, IN2P3/CNRS, École Polytechnique, Palaiseau, France
11  European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
12  Dublin Institute for Advanced Studies, Dublin, Ireland
13  Landessternwarte, Königstuhl, Heidelberg, Germany
14  Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, Grenoble, France
15  DAPNIA/DSM/CEA, CE Saclay, Gif-sur-Yvette, France
16  Unit for Space Physics, North-West University, Potchefstroom, South Africa
17  School of Physics, University of Sydney, Australia
18  Laboratoire de Physique Nucléaire et de Hautes Énergies, IN2P3/CNRS, Universités Paris VI & VII, Paris, France
19  Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, Germany
20  Institute of Particle and Nuclear Physics, Charles University, Prague, Czech Republic
21  Institute of Theoretical Astrophysics, University of Oslo, Norway
22  University of Namibia, Windhoek, Namibia

(Received 3 March 2005 / Accepted 2 June 2005)

Abstract
We report the discovery of very-high-energy (VHE) $\gamma$-ray emission of the binary system PSR B1259-63 / SS 2883 of a radio pulsar orbiting a massive, luminous Be star in a highly eccentric orbit. The observations around the 2004 periastron passage of the pulsar were performed with the four 13 m Cherenkov telescopes of the HESS experiment, recently installed in Namibia and in full operation since December 2003. Between February and June 2004, a $\gamma$-ray signal from the binary system was detected with a total significance above $13\sigma$. The flux was found to vary significantly on timescales of days which makes PSR B1259-63 the first variable galactic source of VHE $\gamma$-rays observed so far. Strong emission signals were observed in pre- and post-periastron phases with a flux minimum around periastron, followed by a gradual flux decrease in the months after. The measured time-averaged energy spectrum above a mean threshold energy of 380 GeV can be fitted by a simple power law $F_0(E/1\,\rm TeV)^{-\Gamma}$ with a photon index $\Gamma =
2.7\pm0.2_\mathrm{stat}\pm0.2_\mathrm{sys}$ and flux normalisation $F_0 = (1.3 \pm 0.1_\mathrm{stat} \pm 0.3_\mathrm{sys})
\times 10^{-12}\,\rm TeV^{-1}\,\rm cm^{-2}\,\rm s^{-1}$. This detection of VHE $\gamma$-rays provides unambiguous evidence for particle acceleration to multi-TeV energies in the binary system. In combination with coeval observations of the X-ray synchrotron emission by the RXTE and INTEGRAL instruments, and assuming the VHE $\gamma$-ray emission to be produced by the inverse Compton mechanism, the magnetic field strength can be directly estimated to be of the order of 1 G.


Key words: gamma-rays: observations -- stars: pulsars: individual: PSR B1259-63

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Editor-in-Chief: T. Forveille
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ISSN: 0004-6361 ; e-ISSN: 1432-0746
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