Abstract
The binary system PSR B1259-63/LS 2883 consists of a 47.8 ms radio pulsar that orbits the companion Be star with a period of 3.4 years in a highly eccentric orbit. In this contribution we report on the discovery of >100 MeV gamma-rays from PSR B1259-63/LS 2883 through the 2010 pariastron passage. This makes PSR B1259-63/LS 2883 the third known GeV gamma-ray binary after LS I +61 303 and LS 5039. Two major flares that occur after the pariastron passage were observed from PSR B1259-63/LS 2883. The fact that the GeV orbital light curve is different from that of the X-ray and TeV light curves strongly suggests that GeV γ-ray emission originates from a different component. We speculate that the observed GeV flares may be resulting from Doppler boosting effects.