The Possible Contribution Of Mature γ-ray Pulsars To Cosmic-ray Positrons

In this thesis, after a brief review about basic properties of pulsars, radiation mechanisms of compact objects and the outer gap models of pulsar's high-energy radiation, I study the possible contribution of mature (age > 10~5yrs) gamma-ray pulsars to cosmic ray positrons based on the revised outer gap. In this model, inclination angle and geometrical effects have been taken into contribution, so more mature pulsars can have outer gap and emit high energy photons. Half of the primary particles in the outer gap will flow back toward the star surface and emit non-thermal photons on the way to the stellar surface through synchrotron radiation, which can produce electron/positron pairs by the cascade of pair production. Part of these pairs will escape from the light cylinder and be accelerated to relativistic energies, which may have a contribution to cosmic electrons and positrons. Based on this model, we first produce the sample of mature pulsars using a Monte Carlo method, determine which one is gamma ray pulsar based on the revised outer gap model, and then estimate the positron contribution from these pulsars. Comparing to the cosmic positron energy spectrum predicted in traditional cosmic ray model, the observed energy spectrum above 10 GeV indicates a obvious excess, our model can explain this excess well.