X-ray Polarimetry of X-ray Pulsars

Abstract

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.

14 pages, 6 figures, invited review for the Special Issue X-ray Polarization: A New Era Begins

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Cited by in corpus (10)

• X-ray polarization from accretion disk winds
• Studying geometry of the ultraluminous X-ray pulsar Swift J0243.6+6124 using X-ray and optical polarimetry
• Variability of X-ray polarization of Cyg X-1
• X-Ray Views of Galactic Accreting Pulsars in High-Mass X-Ray Binaries
• Revealing two orthogonally polarized spectral components in Vela X-1 with IXPE
• Exploring polarization and geometry in the X-ray pulsar 4U 1538-52
• Cyclotron lines in subcritical X-ray pulsars: Monte Carlo simulations reveal the origin of the observed variability
• Probing the polarized emission from the accretion-powered pulsar 4U 1907+09 with IXPE
• Variability study of classical supergiant X-ray binary 4U 1907+09 using NuSTAR
• Shape and ionization of equatorial matter near compact objects from X-ray polarization reflection signatures