SAS-2 observations of high energy gamma rays from discrete sources

Six localized high energy (>35MeV) γ-ray sources have been identified with the SAS-2. Four of these are the radio pulsars, PSR 0531+21, PSR 0833-45, PSR 1818-04 and PSR 1717-46 discovered in a search of 75 radio pulsars. The fact that only one of these is observed in X-rays, and the significant differences in pulse profiles in the γ-ray and radio observations, lead to the speculation that different mechanisms are involved. The observed fluxes (>35MeV) range from 2.0x10-6cm-2sec-1 for PSR 1818-04 to 2.9x10-5cm-2sec for PSR 0833-45 and correspond to luminosities ranging from about 1.2x1037sec-1 for PSR 1717-46 to 2.2x1038sec-1 for PSR 0531+21. This compares to a flux of 1.1x10-5cm-2sec-1 with an estimated luminosity of 6x1039sec-1 for Cygnus X-3, the most luminous of the identified sources. The sixth observed source at (l=195+-0.80, b=4.9+-1.10) has no counterpart at other wave