MAGNETIC COMPTON-INDUCED PAIR CASCADE MODEL FOR GAMMA-RAY PULSARS

Electrons accelerated to relativistic energies in pulsar magnetosphere s will Compton scatter surface thermal emission and nonthermal optical , UV, and soft X-ray emission to gamma-ray energies, thereby initiatin g a pair cascade through synchrotron radiation and magnetic pair produ ction. This process is proposed as the origin of the high-energy radia tion that has been detected from six isolated pulsars. We construct an analytic model of magnetic Compton scattering near the polar cap of i solated pulsar magnetospheres and present approximate analytic derivat ions for scattered spectra, electron energy-loss rates, and photon lum inosities. A Monte Carlo simulation is used to model the pair cascade induced by relativistic electrons scattering photons through the cyclo tron resonance. For simplicity, the primary electrons are assumed to b e monoenergetic and the nonresonant emission is omitted. Assuming that the angle phi(B) between the magnetic and spin axes is approximately equal to the polar-cap angle theta(pc), this model can produce both do uble-peaked and broad single-peaked pulse profiles and account for the trend of harder gamma-ray spectra observed from older pulsars.