Radio pulsars behaviour above 50 MeV

A summary is presented of research concerning the behavior of pulsars at gamma-ray energies based on data gathered by the COS-B satellite. The total number of pulsars analyzed amounted to 117 out of the 330 published in the catalog of Manchester and Taylor (1981). The selection criterion was designed to exclude from the analysis those pulsars for which the compatibility between radio and gamma-ray observations was not assured in terms of precision of measurements. Light curves of the Crab pulsar as derived from COS-B data during the course of five observations spanning five years are presented. Predictions of the pulsed photons arriving at the experiment apparatus are evaluated based on the pulsar characteristics (braking power and distance) and the experiment characteristics (sensitivity area and integration time), which allow an upper limit on the conversion efficiency to be calculated. It is noted that PSR 1929+10, a particularly old radio pulsar (age 3 x 10 to the 6th years), has a low value for conversion efficiency, which shows that the emission process in gamma-rays can stop earlier than 3 x 10 to the 7th years, implying a lower-than-foreseen contribution of pulsars to the observed galactic gamma-ray emission.