Issue |
A&A
Volume 688, August 2024
|
|
---|---|---|
Article Number | A220 | |
Number of page(s) | 8 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/202450131 | |
Published online | 23 August 2024 |
Orbital variability of polarized X-ray radiation reflected from a companion star in X-ray binaries
Department of Physics and Astronomy, 20014 University of Turku, Finland
e-mail: varpu.a.ahlberg@utu.fi
Received:
26
March
2024
Accepted:
2
June
2024
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.
Key words: accretion, accretion disks / polarization / methods: analytical / stars: neutron / X-rays: binaries
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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