X-Ray Polarimetry of the Dipping Accreting Neutron Star 4U 1624-49

0584790 - ASÚ 2025 RIV GB eng J - Journal Article
Saade, M. L. - Kaaret, P. - Gnarini, A. - Dovčiak, Michal - Karas, Vladimír … Total 101 authors
X-Ray Polarimetry of the Dipping Accreting Neutron Star 4U 1624-49.
Astrophysical Journal. Roč. 963, č. 2 (2024), č. článku 133. ISSN 0004-637X. E-ISSN 1538-4357
Institutional support: RVO:67985815
Keywords : X-ray binary stars * neutron stars * X-ray astronomy
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 4.9, year: 2022
Method of publishing: Open access

We present the first X-ray polarimetric study of the dipping accreting neutron star 4U 1624-49 with the Imaging X-ray Polarimetry Explorer. We report a detection of polarization in the nondip time intervals with a confidence level of 99.99%. We find an average polarization degree (PD) of 3.1% +/- 0.7% and a polarization angle of 81 degrees +/- 6 degrees east of north in the 2-8 keV band. We report an upper limit on the PD of 22% during the X-ray dips with 95% confidence. The PD increases with energy, reaching from 3.0% +/- 0.9% in the 4-6 keV band to 6% +/- 2% in the 6-8 keV band. This indicates the polarization likely arises from Comptonization. The high PD observed is unlikely to be produced by Comptonization in the boundary layer or spreading layer alone. It can be produced by the addition of an extended geometrically thin slab corona covering part of the accretion disk, as assumed in previous models of dippers, and/or a reflection component from the accretion disk.
Permanent Link: https://hdl.handle.net/11104/0353668