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Lookup NU author(s): Dr Adam IngramORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2024. The Author(s). Published by the American Astronomical Society.Black hole X-ray binaries exhibit different spectral and timing properties in different accretion states. The X-ray outburst of a recently discovered and extraordinarily bright source, Swift J1727.8-1613, has enabled the first investigation of how the X-ray polarization properties of a source evolve with spectral state. The 2-8 keV polarization degree was previously measured by the Imaging X-ray Polarimetry Explorer (IXPE) to be ≈4% in the hard and hard intermediate states. Here we present new IXPE results taken in the soft state, with the X-ray flux dominated by the thermal accretion disk emission. We find that the polarization degree has dropped dramatically to ≲1%. This result indicates that the measured X-ray polarization is largely sensitive to the accretion state and the polarization fraction is significantly higher in the hard state when the X-ray emission is dominated by upscattered radiation in the X-ray corona. The combined polarization measurements in the soft and hard states disfavor a very high or low inclination of the system.
Author(s): Svoboda J, Dovciak M, Steiner JF, Kaaret P, Podgorny J, Poutanen J, Veledina A, Muleri F, Taverna R, Krawczynski H, Brigitte M, Datta SR, Bianchi S, Munoz-Darias T, Negro M, Rodriguez Cavero N, Castro Segura N, Bollemeijer N, Garcia JA, Ingram A, Matt G, Nathan E, Weisskopf MC, Altamirano D, Baldini L, Capitanio F, Egron E, Emami R, Hu K, Marra L, Mastroserio G, Petrucci P-O, Ratheesh A, Soffitta P, Tombesi F, Yang Y-J, Zhang Y
Publication type: Article
Publication status: Published
Journal: Astrophysical Journal Letters
Year: 2024
Volume: 966
Issue: 2
Print publication date: 10/05/2024
Online publication date: 07/05/2024
Acceptance date: 10/04/2024
Date deposited: 29/05/2024
ISSN (print): 2041-8205
ISSN (electronic): 2041-8213
Publisher: American Astronomical Society
URL: https://doi.org/10.3847/2041-8213/ad402e
DOI: 10.3847/2041-8213/ad402e
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