Analyzing X-ray pulsar profiles: geometry and beam pattern of A 0535+26

TL;DR

This paper uses a decomposition method on RXTE X-ray data of pulsar A 0535+26 to analyze magnetic pole contributions, constraining the system's geometry and beam pattern with a model including relativistic effects.

Contribution

It introduces a novel decomposition approach to pulse profiles to distinguish magnetic pole contributions and constrain pulsar geometry and beam pattern.

Findings

Identified non-antipodal magnetic poles causing pulse asymmetry.

Reconstructed a beam pattern consistent with a hollow column plus scattered halo.

Provided geometric constraints and a model including relativistic light deflection.

Abstract

We applied a decomposition method to the energy dependent pulse profiles of the accreting binary pulsar A 0535+26, in order to identify the contribution of the two magnetic poles of the neutron star and to obtain constraints on the geometry of the system and on the beam pattern. We analyzed pulse profiles obtained from RXTE observations in the X-ray regime. Basic assumptions of the method are that the asymmetry observed in the pulse profiles is caused by non-antipodal magnetic poles and that the emission regions have axisymmetric beam patterns. Constraints on the geometry of the pulsar and a possible solution of the beam pattern are given. We interpreted the reconstructed beam pattern in terms of a geometrical model of a hollow column plus a halo of scattered radiation on the neutron star surface, which includes relativistic light deflection.