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The X-ray polarization of the Seyfert 1 galaxy IC 4329A

Ingram, A; Ewing, M; Marinucci, A; Tagliacozzo, D; Rosario, DJ; Veledina, A; Kim, DE; ... Zane, S; + view all (2023) The X-ray polarization of the Seyfert 1 galaxy IC 4329A. Monthly Notices of the Royal Astronomical Society , 525 (4) pp. 5437-5449. 10.1093/mnras/stad2625. Green open access

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We present an X-ray spectro-polarimetric analysis of the bright Seyfert galaxy IC 4329A. The Imaging X-ray Polarimetry Explorer (IXPE) observed the source for ∼500 ks, supported by XMM–Newton (∼60 ks) and NuSTAR (∼80 ks) exposures. We detect polarization in the 2–8 keV band with 2.97σ confidence. We report a polarization degree of 3.3 ± 1.1 per cent and a polarization angle of 78° ± 10° (errors are 1σ confidence). The X-ray polarization is consistent with being aligned with the radio jet, albeit partially due to large uncertainties on the radio position angle. We jointly fit the spectra from the three observatories to constrain the presence of a relativistic reflection component. From this, we obtain constraints on the inclination angle to the inner disc (<39° at 99 per cent confidence) and the disc inner radius (<11 gravitational radii at 99 per cent confidence), although we note that modelling systematics in practice add to the quoted statistical error. Our spectropolarimetric modelling indicates that the 2–8 keV polarization is consistent with being dominated by emission directly observed from the X-ray corona, but the polarization of the reflection component is completely unconstrained. Our constraints on viewer inclination and polarization degree tentatively favour more asymmetric, possibly out-flowing, coronal geometries that produce more highly polarized emission, but the coronal geometry is unconstrained at the 3σ level.

Type: Article
Title: The X-ray polarization of the Seyfert 1 galaxy IC 4329A
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/stad2625
Publisher version: https://doi.org/10.1093/mnras/stad2625
Language: English
Additional information: © The Author(s) 2023. Published by Oxford University Press on behalf of Royal Astronomical Society This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Keywords: polarization, galaxies: active, galaxies: individual: IC 4329A, galaxies: Seyfert
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10177069
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