Production and beaming of pulsar gamma-ray emission

An analysis of pulsar emission models is performed which demonstrates that the relative phasing of the observed radio and gamma-ray emission from the Vela pulsar and PSR 1747-46 can be explained as an effect of rotational aberration, with the gamma rays originating at or near the stellar surface and the radio emission generated at some distance above the surface. The results also indicate that the pulsed gamma-ray emission from PSR 1818-04 is produced similarly, but that the combination of the magnetic-field configuration near the stellar surface and some shearing of the field far from the surface can lead to surface (gamma-ray) emission which precedes the (radio) emission from large radial distances. It is suggested that the very-high-energy pulsed gamma rays from the Crab pulsar cannot be emitted from the stellar surface, but rather are produced at the light cylinder by the small number of particles with energies greater than 10 to the 14th power eV that can reach the light cylinder along the magnetic axis. The observed variable phase of this emission is tentatively attributed to production of very-high-energy gamma rays along strongly sheared magnetic-field lines at the light cylinder.