SIMBAD references

We reexamine the characteristic polarization angle sweep of rotation-powered pulsars and calculate the expected deviations from this sweep caused by aberrational effects and by polar-cap current flow. We find that in addition to the previously known phase shift of the entire sweep by ΔΦ=-4r/R_L (when R_L is the light cylinder distance), aberration shifts the polarization angle itself by ΔΨ=-(10/3)(r/R_L)cosα. Similarly, current flow above the polar cap shifts the polarization sweep by ΔΨ=(10/3)(r/R_L)(J/J_GL)cosα, potentially providing a method of directly measuring the magnitude of the current. The competition between these two effects produces a potentially observable signature in the polarization angle sweep. Although these effects may appear similar to orthogonal mode shifts, they are an independent phenomenon with distinct observational characteristics.