ANALYZING X-RAY PULSAR PROFILES: ASYMMETRY AS A KEY TO GEOMETRY AND BEAM PATTERN

摘要

We describe a method for analyzing the pulse profiles of accreting X-ray pulsars that is independent of a specific model and involves only a minimum of general assumptions on the system. The starting point is the asymmetry observed in most pulse profiles and the assumption that it is caused by a distorted magnetic dipole field. We find that it is possible to disentangle the contributions of the two emission regions from the pulse profile. Information on geometry and beam pattern can be extracted from these single-pole contributions. In some cases it is possible to determine the locations of the magnetic poles and reconstruct the visible part of the beam pattern. The method is illustrated by two examples, a test case constructed from a model beam pattern and a pulse profile of Cen X-3.