OSSE Upper Limits to Pulsar Gamma-Ray Emission

We present upper limits from CGRO Oriented Scintillation Spectrometer Experiment (OSSE) observations of pulsars and a summary of pulsar observations made with the Compton Gamma Ray Observatory (CGRO). We also report an upper limit to phase-averaged emission for the globular cluster 47 Tuc which is thought to contain many millisecond pulsars. The 2 σ upper limit is 3 × 10^-5 photons cm^-2 s^-1 keV^-1 in the 50-150 keV energy range. The best predictor of a pulsar having a detectable gamma-ray emission appears to be the X-ray luminosities observed by the Röntgen Satellite (ROSAT) (∼0.1-2.4 keV) or the Einstein satellite (∼0.1- 4.0 keV). We compare the gamma-ray data to models related to the inferred magnetic field, the spin-down rate, and/or the frequency. Apparent correlations indicated by the pulsars detected by OSSE and the CGRO Energetic Gamma-Ray Experiment Telescope (EGRET) have counterexamples in all cases.