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A polarimetrically oriented X-ray stare at the accreting pulsar EXO 2030+375

Malacaria, C; Heyl, J; Doroshenko, V; Tsygankov, SS; Poutanen, J; Forsblom, SV; Capitanio, F; ... Thomas, NE; + view all (2023) A polarimetrically oriented X-ray stare at the accreting pulsar EXO 2030+375. Astronomy and Astrophysics , 675 , Article A29. 10.1051/0004-6361/202346581. Green open access

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Abstract

Accreting X-ray pulsars (XRPs) are presumed to be ideal targets for polarization measurements, as their high magnetic field strength is expected to polarize the emission up to a polarization degree of 80%. However, such expectations are being challenged by recent observations of XRPs with the Imaging X-ray Polarimeter Explorer (IXPE). Here, we report on the results of yet another XRP, namely, EXO 2030+375, observed with IXPE and contemporarily monitored with Insight-HXMT and SRG/ART-XC. In line with recent results obtained with IXPE for similar sources, an analysis of the EXO 2030+375 data returns a low polarization degree of 0%- 3% in the phase-averaged study and a variation in the range of 2%- 7% in the phase-resolved study. Using the rotating vector model, we constrained the geometry of the system and obtained a value of 60 for the magnetic obliquity. When considering the estimated pulsar inclination of 130, this also indicates that the magnetic axis swings close to the observera's line of sight. Our joint polarimetric, spectral, and timing analyses hint toward a complex accreting geometry, whereby magnetic multipoles with an asymmetric topology and gravitational light bending significantly affect the behavior of the observed source.

Type: Article
Title: A polarimetrically oriented X-ray stare at the accreting pulsar EXO 2030+375
Open access status: An open access version is available from UCL Discovery
DOI: 10.1051/0004-6361/202346581
Publisher version: https://doi.org/10.1051/0004-6361/202346581
Language: English
Additional information: © The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Keywords: magnetic fields, polarization, stars: neutron, X-rays: binaries, pulsars: individual: EXO 2030+375
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/10174410
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