BeppoSAX observations of the binary pulsar PSR B1259-63

The unique pulsar/Be star system PSR B1259-63/SS2883 [1] had their second “usable” periastron fly-by on May 29 ∼ 19:00 UT ( T ). The original plan of observing the pulsar with the BeppoSAX NFIs some two months before and after periastron and to monitor it during the passage with five, one week interleaved observations, could not be accomplished. PSR B1259-63 was instead observed five times by BeppoSAX during 1997: on March 22 ( T -68 days) and on September 2, 8, 17, 25 ( T +96, 102, 111, 118 days) for a total exposure time of 178.7 ks for each MECS and 36.1 ks for the LECS. Here we present the preliminary results from the spectral and temporal analysis and compare them with previous ROSAT and ASCA observations.