Polarization of High‐Energy Emission from the Crab Pulsar

We investigate polarization of high-energy emissions from the Crab pulsar inthe frame work of the outer gap accelerator, following previous works of Chengand coworkers. The recent version of the outer gap, which extends from insidethe null charge surface to the light cylinder, is used for examining thesynchrotron radiations from the secondary and the tertiary pairs, which areproduced outside the gap. We calculate the light curve, the spectrum and thepolarization characteristics, simultaneously, by taking into account gyrationmotion of the particles. The polarization position angle curve and thepolarization degree are calculated to compare with the Crab optical data. Wedemonstrate that the radiations from inside the null charge surface makeouter-wing and off-pulse emissions in the light curve, and the tertiary pairscontribute to bridge emissions. The emissions from the secondary pairs explainthe main features of the observed light curve and spectrum. On the other hand, both emissions from inside the null charge surface andfrom the tertiary pairs are required to explain the optical polarizationbehavior of the Crab pulsar. The energy dependence of the polarization featuresis expected by the present model. For the Crab pulsar, the polarizationposition angle curve indicates that the viewing angle of the observer measuredfrom the rotational axis is greater than $90^{\circ}$.Comment: 32pages, 8 figures. Accepted for publication in Ap