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Discovery of the Binary Pulsar PSR B1259-63 in Very-High-Energy Gamma Rays around Periastron with H.E.S.S

By F. Aharonian, A.G. Akhperjanian, K.-M. Aye, A.R. Bazer-Bachi, M. Beilicke, W. Benbow, D. Berge, P. Berghaus, K. Bernlohr, 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, S. Johnston, B. Khelifi, J.G. Kirk, Nu. Komin, A. Konopelko, I.J. Latham, R. Le Gallou, A. Lemière, M. Lemoine-Goumard, N. Leroy, O. Martineau-Huynh, 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. Puhlhofer, 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. Sauge, S. Schlenker, R. Schlickeiser, C. Schuster, U. Schwanke, M. Siewert, O. Skjæraasen, H. Sol, R. Steenkamp, C. Stegmann, J.-P. Tavernet, R. Terrier, C.G. Théoret, M. Tluczykont, G. Vasileiadis, C. Venter, P. Vincent, H.J. Volk and S.J. Wagner

Abstract

10 pages, 8 figures, accepted in Astronomy and Astrophysics on 2 June 2005, replace: document unchanged, replaced author field in astro-ph entry - authors are all members of the H.E.S.S. collaboration and three additional authors (99+3, see document)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

Topics: [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], [PHYS.ASTR.CO] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]
Publisher: EDP Sciences
Year: 2005
DOI identifier: 10.1051/0004-6361:20052983
OAI identifier: oai:HAL:in2p3-00024875v1
Provided by: Hal-Diderot
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