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Astronomy and Astrophysics 442 (2005) 1-10
Discovery of the Binary Pulsar PSR B1259-63 in Very-High-Energy Gamma Rays around Periastron with H.E.S.S
F. Aharonian, A.G. Akhperjanian, K.-M. Aye, A.R. Bazer-Bachi, M. Beilicke, W. Benbow, D. Berge, P. Berghaus1, K. Bernlohr, C. Boisson, O. Bolz, I. Braun, F. Breitling, A.M. Brown, J. Bussons Gordo2, P.M. Chadwick, L.-M. Chounet3, R. Cornils, L. Costamante, B. Degrange3, A. Djannati-Ataï1, L.O'C. Drury, G. Dubus3, D. Emmanoulopoulos, P. Espigat1, F. Feinstein2, P. Fleury3, G. Fontaine3, Y. Fuchs, S. Funk, Y.A. Gallant2, B. Giebels3, 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, S. Johnston, B. Khelifi, J.G. Kirk, Nu. Komin, A. Konopelko, I.J. Latham, R. Le Gallou, A. Lemière1, M. Lemoine-Goumard3, N. Leroy3, O. Martineau-Huynh4, T. Lohse, A. Marcowith, C. Masterson, T.J.L. Mccomb, M. De Naurois4, S.J. Nolan, A. Noutsos, K.J. Orford, J.L. Osborne, M. Ouchrif4, M. Panter, G. Pelletier, S. Pita1, G. Puhlhofer, M. Punch1, B.C. Raubenheimer, M. Raue, J. Raux4, S.M. Rayner, I. Redondo3, A. Reimer, O. Reimer, J. Ripken, L. Rob, L. Rolland4, G. Rowell, V. Sahakian, L. Sauge, S. Schlenker, R. Schlickeiser, C. Schuster, U. Schwanke, M. Siewert, O. Skjæraasen, H. Sol, R. Steenkamp2, C. Stegmann, J.-P. Tavernet4, R. Terrier1, C.G. Théoret1, M. Tluczykont3, G. Vasileiadis2, C. Venter, P. Vincent4, H.J. Volk, S.J. Wagner
HESS Collaboration(s)

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 H.E.S.S. 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 $F_0(E/1 TeV)^{-\Gamma}$ with a photon index $\Gamma = 2.7\pm0.2_{stat}\pm0.2_{sys}$ and flux normalisation $F_0 = (1.3\0.1_{stat}\pm0.3_{sys})\times10^{-12} TeV^{-1} cm^{-2} s^{-1}$. 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.
1 :  APC - UMR 7164 - AstroParticule et Cosmologie
2 :  LPTA - Laboratoire de Physique Théorique et Astroparticules
3 :  LLR - Laboratoire Leprince-Ringuet
4 :  LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
Planète et Univers/Astrophysique

Physique/Astrophysique/Cosmologie et astrophysique extra-galactique
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