ON THE ENERGETICS AND NUMBER OF GAMMA-RAY PULSARS

We examine a nearly aligned pulsar model with polar cap acceleration i n order to explain the energetics and number of the known gamma-ray pu lsars. In this model, the efficiency of converting spin-down luminosit y to gamma-ray luminosity increases with decreasing spin-down luminosi ty, a trend recently emphasized by Ulmer. The predicted gamma-ray flux is proportional to P3/4/P5/4d2, where P is the period, P is the perio d derivative, and d is the distance to the pulsar. For initial spin pe riods between almost-equal-to 10 and 30 ms and neutron star polar magn etic fields between almost-equal-to 1 and 4 TG, this model accounts fo r the number and age distribution of the five pulsars which have been observed to emit gamma rays at energies greater than 100 MeV. Implicat ions for pulsar studies are considered.