EUROPEAN SPACE AGENCY

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

DOI: 10.1051/0004-6361:20052983 Bibcode: 2005A&A...442....1A

Raux, J.; Ripken, J.; Funk, S.; Lemoine-Goumard, M.; Reimer, A.; Reimer, O.; Venter, C.; Schlickeiser, R.; Giebels, B.; Fontaine, G.; Benbow, W.; Hauser, M.; Boisson, C.; Gillessen, S.; Aharonian, F.; Akhperjanian, A. G.; Aye, K. -M.; Bazer-Bachi, A. R.; Beilicke, M.; Berge, D.; Berghaus, P.; Bernlöhr, K.; Bolz, O.; Braun, I.; Breitling, F.; Brown, A. M.; Bussons Gordo, J.; Chadwick, P. M.; Chounet, L. -M.; Cornils, R.; Costamante, L.; Degrange, B.; Djannati-Ataï, A.; O'C. Drury, L.; Dubus, G.; Emmanoulopoulos, D.; Espigat, P.; Feinstein, F.; Fleury, P.; Fuchs, Y.; Gallant, Y. A.; Glicenstein, J. F.; Goret, P.; Hadjichristidis, C.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Holleran, M.; Horns, D.; de Jager, O. C.; Johnston, S.; Khélifi, B.; Kirk, J. G.; Komin, Nu.; Konopelko, A.; Latham, I. J.; Le Gallou, R.; Lemière, A.; Leroy, N.; Martineau-Huynh, O.; Lohse, T.; Marcowith, A.; Masterson, C.; McComb, T. J. L.; de Naurois, M.; Nolan, S. J.; Noutsos, A.; Orford, K. J.; Osborne, J. L.; Ouchrif, M.; Panter, M.; Pelletier, G.; Pita, S.; Pühlhofer, G.; Punch, M.; Raubenheimer, B. C.; Raue, M.; Rayner, S. M.; Redondo, I.; Rob, L.; Rolland, L.; Rowell, G.; Sahakian, V.; Saugé, L.; Schlenker, S.; Schuster, C.; Schwanke, U.; Siewert, M.; Skjæraasen, O.; Sol, H.; Steenkamp, R.; Stegmann, C.; Tavernet, J. -P.; Terrier, R.; Théoret, C. G.; Tluczykont, M.; Vasileiadis, G.; Vincent, P.; Völk, H. J.; Wagner, S. J.

Germany, Armenia, United Kingdom, France, Ireland, South Africa, Australia, Czech Republic, Norway, Namibia

Abstract

We report the discovery of very-high-energy (VHE) γ-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 γ-ray signal from the binary system was detected with a total significance above 13σ. The flux was found to vary significantly on timescales of days which makes PSR B1259-63 the first variable galactic source of VHE γ-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)-Γ with a photon index Γ = 2.7±0.2_stat±0.2_sys and flux normalisation F0 = (1.3 ± 0.1_stat ± 0.3_sys) × 10-12 TeV-1 cm-2 s-1. This detection of VHE γ-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 γ-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.

2005 • Astronomy and Astrophysics
INTEGRAL 375
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