Discovery of energy-dependent phase variations in the polarization angle of Cen X-3

Qing-Chang Zhao; Lian Tao; Sergey S. Tsygankov; Juri Poutanen; Hua Feng; Shuang-Nan Zhang; Hancheng Li; Mingyu Ge; Liang Zhang; Alexander A. Mushtukov

arXiv · 2603.02780

Discovery of energy-dependent phase variations in the polarization angle of Cen X-3

Qing-Chang Zhao·Lian Tao·Sergey S. Tsygankov·Juri Poutanen·Hua Feng·Shuang-Nan Zhang·Hancheng Li·Mingyu Ge·Liang Zhang·Alexander A. Mushtukov

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Abstract

We present a detailed polarimetric analysis of Cen X-3 using \ixpe observations during its high state, revealing 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 (PA) is strongly phase-dependent, with dramatic variations visible in a few specific phase intervals. We model 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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Qing-Chang Zhao, Lian Tao, Sergey S. Tsygankov, Juri Poutanen, Hua Feng, Shuang-Nan Zhang, Hancheng Li, Mingyu Ge, Liang Zhang, Alexander A. Mushtukov. 2026-03-03. Discovery of energy-dependent phase variations in the polarization angle of Cen X-3. https://arxiv.org/abs/2603.02780

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