A2 Refereed review article in a scientific journal
X-ray Polarimetry of X-ray Pulsars
Authors: Poutanen, Juri; Tsygankov, Sergey S.; Forsblom, Sofia V.
Publisher: MDPI
Publishing place: BASEL
Publication year: 2024
Journal: Galaxies
Journal name in source: GALAXIES
Journal acronym: GALAXIES
Article number: 46
Volume: 12
Issue: 4
Number of pages: 14
eISSN: 2075-4434
DOI: https://doi.org/10.3390/galaxies12040046
Web address : https://doi.org/10.3390/galaxies12040046
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/457824456
Radiation from X-ray pulsars (XRPs) was expected to be strongly linearly polarized owing to a large difference in their ordinary and extraordinary mode opacities. The launch of IXPE allowed us to check this prediction. IXPE observed a dozen X-ray pulsars, discovering pulse-phase dependent variation of the polarization degree (PD) and polarization angle (PA). Although the PD showed rather erratic profiles resembling flux pulse dependence, the PA in most cases showed smooth variations consistent with the rotating vector model (RVM), which can be interpreted as a combined effect of vacuum birefringence and dipole magnetic field structure at a polarization-limiting (adiabatic) radius. Application of the RVM allowed us to determine XRP geometry and to confirm the free precession of the NS in Her X-1. Deviations from RVM in two bright transients led to the discovery of an unpulsed polarized emission likely produced by scattering off the accretion disk wind.
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Funding information in the publication:
This research was supported by the Academy of Finland grants 333112 and 349144.
