298 articles – 2259 Notices  [english version]
 HAL : in2p3-00024875, version 1
 arXiv : astro-ph/0506280
 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
 HESS Collaboration(s)
 (2005)
 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.
 Thème(s) : Planète et Univers/AstrophysiquePhysique/Astrophysique/Cosmologie et astrophysique extra-galactique
 Lien vers le texte intégral : http://fr.arXiv.org/abs/astro-ph/0506280
 in2p3-00024875, version 1 http://hal.in2p3.fr/in2p3-00024875 oai:hal.in2p3.fr:in2p3-00024875 Contributeur : Dominique Girod <> Soumis le : Lundi 30 Octobre 2006, 20:54:43 Dernière modification le : Lundi 30 Octobre 2006, 21:03:51