X-ray Polarimetry of X-ray Pulsars

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Hauptverfasser: Poutanen, Juri, Tsygankov, Sergey S., Forsblom, Sofia V.
Format: Preprint
Veröffentlicht: 2024
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author Poutanen, Juri
Tsygankov, Sergey S.
Forsblom, Sofia V.
author_facet Poutanen, Juri
Tsygankov, Sergey S.
Forsblom, Sofia V.
contents 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.
format Preprint
id arxiv_https___arxiv_org_abs_2408_04431
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle X-ray Polarimetry of X-ray Pulsars
Poutanen, Juri
Tsygankov, Sergey S.
Forsblom, Sofia V.
High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
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.
title X-ray Polarimetry of X-ray Pulsars
topic High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2408.04431