Orbital variability of polarized X-ray radiation reflected from a companion star in X-ray binaries

Fuente: arXiv
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Autori principali: Ahlberg, Varpu, Kravtsov, Vadim, Poutanen, Juri
Natura: Preprint
Pubblicazione: 2024
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author Ahlberg, Varpu
Kravtsov, Vadim
Poutanen, Juri
author_facet Ahlberg, Varpu
Kravtsov, Vadim
Poutanen, Juri
contents The reflection of X-ray radiation produced near a compact object from its stellar companion contributes to the orbital variability of polarization in X-ray binaries. The X-rays are reflected mainly via Thomson scattering resulting in a high polarization. The orbital variability of the polarization strongly depends on the inclination and the orbital parameters allowing us to constrain them. To explore this phenomenon, we present analytical single-scattering models for the polarized reflection. We find that while diluted by the direct emission, the reflection can produce a polarization degree of about 1$\%$ in the case of a large reflection albedo. We fitted the orbital variations of the X-ray polarization observed by the Imaging X-ray Polarimetry Explorer from an accreting weakly magnetized neutron star `clocked burster' GS 1826$-$238 and found that the amplitude of the variations is too large to be primarily caused by the companion star. The polarized reflection is more significant if the compact object is obscured from the observer, and thus it should be more easily observable in certain high-inclination targets.
format Preprint
id arxiv_https___arxiv_org_abs_2403_17644
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Orbital variability of polarized X-ray radiation reflected from a companion star in X-ray binaries
Ahlberg, Varpu
Kravtsov, Vadim
Poutanen, Juri
High Energy Astrophysical Phenomena
The reflection of X-ray radiation produced near a compact object from its stellar companion contributes to the orbital variability of polarization in X-ray binaries. The X-rays are reflected mainly via Thomson scattering resulting in a high polarization. The orbital variability of the polarization strongly depends on the inclination and the orbital parameters allowing us to constrain them. To explore this phenomenon, we present analytical single-scattering models for the polarized reflection. We find that while diluted by the direct emission, the reflection can produce a polarization degree of about 1$\%$ in the case of a large reflection albedo. We fitted the orbital variations of the X-ray polarization observed by the Imaging X-ray Polarimetry Explorer from an accreting weakly magnetized neutron star `clocked burster' GS 1826$-$238 and found that the amplitude of the variations is too large to be primarily caused by the companion star. The polarized reflection is more significant if the compact object is obscured from the observer, and thus it should be more easily observable in certain high-inclination targets.
title Orbital variability of polarized X-ray radiation reflected from a companion star in X-ray binaries
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2403.17644