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

We describe a refined calculation of high energy emission from rotation-powered pulsars based on the Outer Gap model of Cheng, Ho \&~Ruderman (1986a,b). 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 {\it 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.Comment: 13 pages, LaTeX, for figures send request to [email protected]

The Spectral Energy Distribution of the High-Z Blazar Q0906+693

We describe further observations of QSO J0906+6930, a z=5.48 blazar likely to be detected in gamma-rays. New radio and X-ray data place significant constraints on any kpc-scale extension of the VLBA-detected jet. Improved optical spectroscopy detects absorption from an intervening galaxy at z=1.849 and raise the possibility that this distant, bright source is lensed. We combine the new data into an improved SED for the blazar core and comment on the Compton keV-GeV flux component.Comment: 10pp, 3 figures, accpeted for publication in the Astronomical Journa

Altitude Limits for Rotating Vector Model Fitting of Pulsar Polarization

Traditional pulsar polarization sweep analysis starts from the point dipole rotating vector model (RVM) approximation. If augmented by a measurement of the sweep phase shift, one obtains an estimate of the emission altitude (Blaskiewicz, Cordes, & Wasserman). However, a more realistic treatment of field line sweepback and finite altitude effects shows that this estimate breaks down at modest altitude ~ 0.1R_{LC}. Such radio emission altitudes turn out to be relevant to the young energetic and millisecond pulsars that dominate the \gamma-ray population. We quantify the breakdown height as a function of viewing geometry and provide simple fitting formulae that allow observers to correct RVM-based height estimates, preserving reasonable accuracy to R ~ 0.3R_{LC}. We discuss briefly other observables that can check and improve height estimates