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Lookup NU author(s): Melissa Ewing, Dr Adam IngramORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2025 The Author(s).We report the first detection of the X-ray polarization of the transient black hole X-ray binary IGR J17091-3624 taken with the Imaging X-ray polarimetry Explorer (IXPE) in 2025 March, and present the results of an X-ray spectropolarimetric analysis. The polarization was measured in the 2-8 keV band with statistical confidence. We report a polarization degree (PD) of per cent and a polarization angle of (errors are confidence). There is a hint of a positive correlation of PD with energy that is not statistically significant. We report that the source is in the corona-dominated hard state, which is confirmed by a hard power-law-dominated spectrum with weak reflection features and the presence of a Type-C quasi-periodic oscillation at Hz. The orientation of the emitted radio jet is not known, and so we are unable to compare it with the direction of X-ray polarization, but we predict the two to be parallel if the geometry is similar to that in Cygnus X-1 and Swift J1727.8-1613, the two hard state black hole binaries previously observed by IXPE. In the Comptonization scenario, the high observed PD requires a very favourable geometry of the corona, a high inclination angle (supported by the presence of a dip in the light curve) and possibly a mildly relativistic outflow and/or scattering in an optically thick wind.
Author(s): Ewing M, Parra M, Mastroserio G, Veledina A, Ingram A, Dovciak M, Garcia JA, Russell TD, Baglio MC, Poutanen J, Adegoke O, Bianchi S, Capitanio F, Connors R, Del Santo M, De Marco B, Trigo MD, Gandhi P, Gupta M, Kang C, Kammoun E, Loktev V, Marra L, Matt G, Nathan E, Petrucci P-O, Shidatsu M, Steiner JF, Tombesi F, Vincentelli FM
Publication type: Article
Publication status: Published
Journal: Monthly Notices of the Royal Astronomical Society
Year: 2025
Volume: 541
Issue: 2
Pages: 1774-1781
Print publication date: 01/08/2025
Online publication date: 27/05/2025
Acceptance date: 22/05/2025
Date deposited: 04/08/2025
ISSN (print): 0035-8711
ISSN (electronic): 1365-2966
Publisher: Oxford University Press
URL: https://doi.org/10.1093/mnras/staf859
DOI: 10.1093/mnras/staf859
Data Access Statement: IXPE data are publicly available from the HEASARC data archive (https://heasarc.gsfc.nasa.gov)
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