Relativistic Effects and Polarization in Three High‐Energy Pulsar Models

We present the influence of the special relativistic effects of aberrationand light travel time delay on pulsar high-energy lightcurves and polarizationcharacteristics predicted by three models: the two-pole caustic model, theouter gap model, and the polar cap model. Position angle curves and degree ofpolarization are calculated for the models and compared with the optical dataon the Crab pulsar. The relative positions of peaks in gamma-ray and radiolightcurves are discussed in detail for the models. We find that the two-polecaustic model can reproduce qualitatively the optical polarizationcharacteristics of the Crab pulsar - fast swings of the position angle andminima in polarization degree associated with both peaks. The anticorrelationbetween the observed flux and the polarization degree (observed in the opticalband also for B0656+14) naturally results from the caustic nature of the peakswhich are produced in the model due to the superposition of radiation from manydifferent altitudes, ie. polarized at different angles. The two-pole causticmodel also provides an acceptable interpretation of the main features in theCrab's radio profile. Neither the outer gap model nor the polar cap model areable to reproduce the optical polarization data on the Crab. Although the outergap model is very successful in reproducing the relative positions of gamma-rayand radio peaks in pulse profiles, it can reproduce the high-energy lightcurvesonly when photon emission from regions very close to the light cylinder isincluded.Comment: 49 pages, 14 figures, 1 table, submitted to Ap