X-ray polarization of accreting black holes: Cyg X-1 and Swift J1727.8-1613

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Main Authors: Brigitte, M., Svoboda, J.
Format: Preprint
Published: 2025
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author Brigitte, M.
Svoboda, J.
author_facet Brigitte, M.
Svoboda, J.
contents The Imaging X-ray Polarimetry Explorer is an X-ray observatory measuring the X-ray polarization in the 2-8 keV energy range. Highly sensitive to the system's geometry, X-ray polarization is a unique method to probe the structure of X-ray binaries. The Imaging X-ray Polarimetry Explorer observed the High-Mass X-ray Binary Cygnus X-1 and the Low-Mass X-ray Binary Swift J1727.8-1613 in different accretion states: in the hard state and in the soft state. The X-ray polarimetry analysis of both sources shows a linear polarization degree increasing with energy, with higher values in the hard state than in the soft state. However, the linear polarization angle stays similar in both states and is aligned with the radio jet within $5^\circ$. Furthermore, the Low-Mass X-ray Binary Swift J1727.8-1613 has a lower optical intrinsic polarization and a lower X-ray polarization degree for a softer spectrum. The similarities observed in this analysis between the X-ray polarization results of different types of X-ray Binaries show that the innermost accretion processes are independent of the companion star's type.
format Preprint
id arxiv_https___arxiv_org_abs_2504_10981
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle X-ray polarization of accreting black holes: Cyg X-1 and Swift J1727.8-1613
Brigitte, M.
Svoboda, J.
High Energy Astrophysical Phenomena
The Imaging X-ray Polarimetry Explorer is an X-ray observatory measuring the X-ray polarization in the 2-8 keV energy range. Highly sensitive to the system's geometry, X-ray polarization is a unique method to probe the structure of X-ray binaries. The Imaging X-ray Polarimetry Explorer observed the High-Mass X-ray Binary Cygnus X-1 and the Low-Mass X-ray Binary Swift J1727.8-1613 in different accretion states: in the hard state and in the soft state. The X-ray polarimetry analysis of both sources shows a linear polarization degree increasing with energy, with higher values in the hard state than in the soft state. However, the linear polarization angle stays similar in both states and is aligned with the radio jet within $5^\circ$. Furthermore, the Low-Mass X-ray Binary Swift J1727.8-1613 has a lower optical intrinsic polarization and a lower X-ray polarization degree for a softer spectrum. The similarities observed in this analysis between the X-ray polarization results of different types of X-ray Binaries show that the innermost accretion processes are independent of the companion star's type.
title X-ray polarization of accreting black holes: Cyg X-1 and Swift J1727.8-1613
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2504.10981