First detection of X-ray polarization from the long-period X-ray pulsar 4U 1954+319
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| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866910251558633472 |
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| author | Salganik, Alexander Kong, Lingda Forsblom, Sofia V. Zhou, Menglei Liu, Honghui Zhao, QingChang Tsygankov, Sergey S. Santangelo, Andrea Poutanen, Juri |
| author_facet | Salganik, Alexander Kong, Lingda Forsblom, Sofia V. Zhou, Menglei Liu, Honghui Zhao, QingChang Tsygankov, Sergey S. Santangelo, Andrea Poutanen, Juri |
| contents | We report the first detection of X-ray polarization with the Imaging X-ray Polarimetry Explorer from the X-ray pulsar (XRP) 4U 1954$+$319. The source belongs to an extremely rare class of systems in which a slowly rotating neutron star accretes from the dense wind of a red supergiant companion. We detect coherent pulsations at $P_{\rm spin}=5.49\pm0.05$ h, which is one of the longest spin periods known among XRPs. While the phase-averaged analysis shows no significant polarization, with a 99% confidence minimum detectable polarization (MDP$_{99}$) of 4.9% in the 2-8 keV band, the phase-resolved analysis shows a single interval at pulse maximum in which the polarization degree (PD) exceeds the MDP$_{99}$, yielding ${\rm PD}=10.2_{-3.0}^{+3.1}$%. The polarization angle (PA) exhibits a smooth $\approx150^{\circ}$ rotation over the pulse, and a joint evaluation of all phase bins yields an overall detection significance of $3.3σ$. Using the rotating vector model, we identify a geometric solution that reproduces the observed PA variation. From this model, we infer a phase-independent ${\rm PD}$ of $6.1\pm1.1$% in the 2-8 keV band. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2512_08195 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | First detection of X-ray polarization from the long-period X-ray pulsar 4U 1954+319 Salganik, Alexander Kong, Lingda Forsblom, Sofia V. Zhou, Menglei Liu, Honghui Zhao, QingChang Tsygankov, Sergey S. Santangelo, Andrea Poutanen, Juri High Energy Astrophysical Phenomena We report the first detection of X-ray polarization with the Imaging X-ray Polarimetry Explorer from the X-ray pulsar (XRP) 4U 1954$+$319. The source belongs to an extremely rare class of systems in which a slowly rotating neutron star accretes from the dense wind of a red supergiant companion. We detect coherent pulsations at $P_{\rm spin}=5.49\pm0.05$ h, which is one of the longest spin periods known among XRPs. While the phase-averaged analysis shows no significant polarization, with a 99% confidence minimum detectable polarization (MDP$_{99}$) of 4.9% in the 2-8 keV band, the phase-resolved analysis shows a single interval at pulse maximum in which the polarization degree (PD) exceeds the MDP$_{99}$, yielding ${\rm PD}=10.2_{-3.0}^{+3.1}$%. The polarization angle (PA) exhibits a smooth $\approx150^{\circ}$ rotation over the pulse, and a joint evaluation of all phase bins yields an overall detection significance of $3.3σ$. Using the rotating vector model, we identify a geometric solution that reproduces the observed PA variation. From this model, we infer a phase-independent ${\rm PD}$ of $6.1\pm1.1$% in the 2-8 keV band. |
| title | First detection of X-ray polarization from the long-period X-ray pulsar 4U 1954+319 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2512.08195 |