HEAO-3 UPPER LIMITS TO PULSED GAMMA-RAY EMISSION FROM PSR-1509-58 AND PSR-0833-45

We report upper limits to the 50 keV-10 MeV gamma-ray pulsations from PSR 1509-58 and PSR 0833-45 (Vela) made with the HEAO 3 gamma-ray spectrometer. The 2-sigma upper limit to the 50-300 keV flux from PSR 1509-58 is 6.9 x 10(-6) photons cm-2 s-1 keV-1. Combined with the best-fit X-ray spectrum, this limit suggests there is a break in the spectrum below approximately 100 keV. This upper limit is not stringent enough, however, to distinguish between thermal and nonthermal models for the source of the X-ray emission. The 2-sigma upper limit to the 3.2-10 MeV flux from PSR 0833-45 is 4.9 x 10(-8) photons cm-2 s-1 keV-1.