PSR B 1259-63/SS2883 is a binary system consisting of a 48ms radio pulsar orbiting a Be star with a period of 3.4y in a highly eccentric orbit (e = 0.87). The system was first detected in very-high-energy (VHE) gamma-rays by H.E.S.S. around the last periastron passage in March 2004 (March 7, 2004). These observations established PSR B1259-63/SS2883 as the first variable galactic source in the VHE regime. A light curve for the system covering mainly the post periastron part could be deduced, clearly showing a variable flux in VHE photons. New data have been taken this year from April to June with the system approaching its next periastron (July 27, 2007). A preliminary data analysis will be presented and compared with model predictions for this very interesting system.

H.E.S.S. Collaboration

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 2 (OG part 1), pages 703-706