An Outer Gap Model of High-Energy Emission from Rotation-Powered Pulsars

We describe a refined calculation of high energy emission from rotationpowered pulsars based on the Outer Gap model of Cheng, Ho & Ruderman (1986a,b). In this calculation, vacuum gaps form in regions near the speed-oflight cylinder of the pulsar magnetosphere along the boundary between the closed and open field line zones. We have improved upon previous efforts to model the spectra from these pulsars (e. g. Cheng, et al. 1986b; Ho 1989) by following the variation in particle production and radiation properties with position in the outer gap. Curvature, synchrotron and inverse-Compton scattering fluxes vary significantly over the gap and their interactions via photon-photon pair production build up the radiating charge populations at varying rates. We have also incorporated an approximate treatment of the transport of particle and photon fluxes between gap emission zones. These effects, along with improved computations of the particle and photon distributions, provide very important modifications of the model gamma-ray flux. In particular, we attempt to make specific predictions of pulse profile shapes and spectral variations as a function of pulse phase and suggest further extensions to the model which may provide accurate computations of the observed high energy emissions. Subject headings: gamma-rays: emission — pulsars: gamma rays Present Address: CITA, 60 St. George St., Toronto, Canada, M5S 1A1 Alfred P. Sloan Foundation Fellow