A1 Refereed original research article in a scientific journal
Discovery of energy-dependent phase variations in the polarization angle of Cen X-3
Authors: Zhao, Qing-Chang; Tao, Lian; Tsygankov, Sergey S.; Poutanen, Juri; Feng, Hua; Zhang, Shuang-Nan; Li, Hancheng; Ge, Mingyu; Zhang, Liang; Mushtukov, Alexander A.
Publisher: EDP Sciences
Publication year: 2026
Journal: Astronomy and Astrophysics
Article number: A94
Volume: 708
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202556184
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Open Access publication channel
Web address : https://doi.org/10.1051/0004-6361/202556184
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/523438696
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
We present a detailed polarimetric analysis of Cen X-3 using IXPE observations during its high state, revealing a complex, energy-dependent polarization behavior. While phase-averaged polarization shows marginal energy dependence, phase-resolved analysis reveals that the energy dependence of the polarization angle is strongly phase-dependent, with dramatic variations visible in a few specific phase intervals. We modeled this behavior using a two-component polarization framework consisting of a pulsed component governed by the rotating vector model (RVM) and an additional phase-dependent component. By allowing the additional component’s polarized flux to vary with pulse phase while fixing its PA, the observed complex behavior can be reconciled with a single set of RVM parameters across all energies. Spectroscopic analysis using IXPE, NICER, and NuSTAR during the high state reveals phase-modulated intrinsic hydrogen column density and covering fraction, suggesting that the wind properties are modulated with pulse phase. Our findings indicate that phase-dependent scattering in the disk wind may significantly alter the observed polarization properties of X-ray pulsars.
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Funding information in the publication:
Financial support for this work is provided by the National Key R&D Program of China (2021YFA0718500). We also acknowledge funding from the National Natural Science Foundation of China (NSFC) under grant numbers 12122306, 12333007, and U2038102. We acknowledge support from the China’s Space Origins Exploration Program. This research was supported by the International Space Science Institute (ISSI) in Bern, through International Team project 25-657 ‘Polarimetric Insights into Extreme Magnetism’. SST and JP acknowledge support by the Research Council of Finland, the Centre of Excellence in Neutron-Star Physics (project 374064).
