High-precision geometry of a double-pole pulsar

Abstract

High time resolution observations of PSR B0906-49 (or PSR J0908-4913) over a wide range of frequencies have enabled us to determine the geometry and beam shape of the pulsar. We have used the position angle traverse to determine highly constrained solutions to the rotating vector model which shows conclusively that PSR B0906-49 is an orthogonal rotator. The accuracy obtained in measuring the geometry is unprecedented. This may allow tests of high-energy emission models, should the pulsar be detected with Gamma-Ray Large Area Space Telescope. Although the impact parameter β appears to be frequency dependent, we have shown that this is due to the effect of interstellar scattering. As a result, this pulsar provides some of the strongest evidence yet that the position angle swing is indeed related to a geometrical origin, at least for non-recycled pulsars. We have shown that the beam structures of the main pulse and interpulse in PSR B0906-49 are remarkably similar. The emission comes from a height of ∼230 km, and is consistent with originating in a patchy cone located about halfway to the last open field lines. The rotation axis and direction of motion of the pulsar appear to be aligned. © 2008 RAS.