Di Marco, A;
La Monaca, F;
Poutanen, J;
Wu, K;
Zane, S;
Turolla, R;
et, al;
(2023)
First detection of X-ray polarization from the accreting neutron star 4U 1820−303.
The Astrophysical Journal Letters
, 953
(2)
, Article L22.
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Abstract
This paper reports the first detection of polarization in the X-rays for atoll-source 4U 1820−303, obtained with the Imaging X-ray Polarimetry Explorer (IXPE) at 99.999% confidence level (CL). Simultaneous polarimetric measurements were also performed in the radio with tha Australia Telescope Compact Array (ATCA). The IXPE observations of 4U 1820−303 were coordinated with Swift-XRT, X-ray polarimetry of 4U 1820−303 3 NICER, and NuSTAR aiming to obtain an accurate X-ray spectral model covering a broad energy interval. The source shows a significant polarization above 4 keV, with a polarization degree of 2.0% ± 0.5% and a polarization angle of −55◦ ± 7 ◦ in the 4–7 keV energy range, and a polarization degree of 10%±2% and a polarization angle of −67◦±7 ◦ in the 7–8 keV energy bin. This polarization also shows a clear energy trend with polarization degree increasing with energy and a hint for a position-angle change of ≃ 90 deg at 96% CL around 4 keV. The spectro-polarimetric fit indicates that the accretion disk is polarized orthogonally to the hard spectral component, which is presumably produced in the boundary/spreading layer. We do not detect linear polarization from the radio counterpart, with a 3σ upper limit of 50% at 7.25 GHz.
| Type: | Article |
|---|---|
| Title: | First detection of X-ray polarization from the accreting neutron star 4U 1820−303 |
| Open access status: | An open access version is available from UCL Discovery |
| Publisher version: | https://doi.org/10.3847/2041-8213/acec6e |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third-party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| Keywords: | Accretion, accretion disks – polarization – stars: individual: 4U 1820−303 – stars: neutron – X-ray binaries |
| 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/10174559 |
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