Gamma-ray emission from young neutron stars

A significant fraction of the diffuse galactic γ-ray emission at high energies (E≥10 MeV) might be due to unresolved point sources. The most promising candidates are radio pulsars. To date, only the Crab and Vela pulsar have been unambiguously identified in the high energy band. For several other pulsars γ-ray emission has been suggested, but the data are not conclusive. For the unique source Geminga a neutron star association was recently suggested from X-ray and optical studies. Some of the ∼20 unidentified COS B sources emitting significant flux in this band might also involve neutron stars. An evolutionary link between these object classes was suggested by Ruderman and Cheng.²⁵ To improve our understanding of the nature and evolution of these sources, high energy γ-ray observations could provide the best available diagnostic tools. Using recent radio data of pulsars, we determine likely candidates for pulsed γ-ray emission using the emission models of Cheng et al. and Harding. The recent detection of pulsed γ-rays from PSR 1951+32 lends observational support to the scenario of Cheng et al. which also suggests that PSR 1855+09 might be another excellent γ-ray pulsar candidate for which observations with the Gamma Ray Observatory should receive high priority. We also discuss the possible contribution of young neutron stars to the diffuse galactic high energy glow.