Photon capture in pulsar magnetic fields

Abstract

We investigate the process of photon capture by strong magnetic fields, by transforming it into a positronium, and the subsequent decay of the positronium into two photons. We discuss the implications of this process for the polar gap models of pulsars. We find that the capture process is energy-dependent and photons above a certain energy (depending on the magnetic field) are not captured and can decay into electron-positron pairs. This leads to increased gap heights in the modle and leads to higher luminosities than found earlier. We also find that it may be possible for very high-energy positronia to escape the magnetosphere of the pulsar and be observed near the Earth as photons in agreement with the recent observations of 10¹² eV gamma-rays from some pulsars.