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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 doi link

Author(s): Aharonian F., Berghaus P., Bussons Gordo J., Chounet L.-M., Degrange B., Djannati-Ataï A., Dubus G., Espigat P., Feinstein F., Fleury P., Fontaine G., Gallant Y., Giebels B., Lemière A., Lemoine-Goumard M., Leroy N., Martineau-Huynh O., Marcowith A., De Naurois M., Ouchrif M., Pita S., Punch M., Raux J., Redondo I., Rolland L., Steenkamp R., Tavernet J.-P., Terrier R., Théoret C.G., Vasileiadis G.

(Article) Published: Astronomy & Astrophysics, vol. 442 p.1-10 (2005)
Links openAccess full text : arxiv


Ref HAL: in2p3-00024875_v1
Ref Arxiv: astro-ph/0506280
DOI: 10.1051/0004-6361:20052983
Ref. & Cit.: NASA ADS
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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 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.



Comments: 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)