PULSED HIGH-ENERGY GAMMA-RAYS FROM THE RADIO PULSAR PSR1706-44

OF the more than 500 known radio pulsars, only three have been detected as gamma-ray sources. Using the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory satellite, we have detected pulsed gamma-radiation, above 100 MeV in energy, from a fourth radio pulsar, PSR1706-44. Within the pulse period of 102 ms, the gamma-emission forms a single broad peak, in contrast to the two narrow peaks seen in the other high-energy gamma-ray pulsars. The emission mechanism in all cases is probably the same, the differences arising from the geometry of the magnetic and rotation axes and the line of sight. In these pulsars, gamma-ray emission accounts for as much as 1% of the total neutron star spin-down energy, much more than emerges at optical or radio frequencies, so study of this emission is important in understanding pulsar emission and evolution.