Sco X-1 as seen by IXPE
Fuente:
arXiv
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866918159853813760 |
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| author | La Monaca, Fabio |
| author_facet | La Monaca, Fabio |
| contents | The X-ray polarization of Sco X-1 was measured for the first time with very high significance by the Imaging X-ray Polarimeter Explorer (IXPE). A polarization degree of 1.0% $\pm$ 0.2% at a PA of 8° $\pm$ 6° at 90% confidence level (CL) in the 2-8 keV energy band is obtained, while the source was in its soft state with short flaring periods. The source state was determined by a strictly simultaneous X-ray observation campaign jointly with IXPE, which involved NICER, NuSTAR, and Insight-HXMT, allowing for a broad-band spectrum characterization and study of quasiperiodic oscillations. The spectropolarimetric analysis yielded a polarization of <3.2% for the accretion disk and a polarization of 1.3% $\pm$ 0.4% for the hard Comptonized component. A constraint on the polarization of the reflection component, modeled using relxillNS, is obtained. All the results about the polarization degree match the theoretical expectations, while the polarization angle of 8° +/- 6° at 90% CL shows a rotation of 46° $\pm$ 9° with respect to the measured position angle of the radio jet and previous marginal results by PolarLight. This may suggest a variation in the polarization angle related to the source state, which is linked to the variation of corona geometry as reported by IXPE observations of Z sources, or possibly to relativistic precession. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_07181 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Sco X-1 as seen by IXPE La Monaca, Fabio High Energy Astrophysical Phenomena The X-ray polarization of Sco X-1 was measured for the first time with very high significance by the Imaging X-ray Polarimeter Explorer (IXPE). A polarization degree of 1.0% $\pm$ 0.2% at a PA of 8° $\pm$ 6° at 90% confidence level (CL) in the 2-8 keV energy band is obtained, while the source was in its soft state with short flaring periods. The source state was determined by a strictly simultaneous X-ray observation campaign jointly with IXPE, which involved NICER, NuSTAR, and Insight-HXMT, allowing for a broad-band spectrum characterization and study of quasiperiodic oscillations. The spectropolarimetric analysis yielded a polarization of <3.2% for the accretion disk and a polarization of 1.3% $\pm$ 0.4% for the hard Comptonized component. A constraint on the polarization of the reflection component, modeled using relxillNS, is obtained. All the results about the polarization degree match the theoretical expectations, while the polarization angle of 8° +/- 6° at 90% CL shows a rotation of 46° $\pm$ 9° with respect to the measured position angle of the radio jet and previous marginal results by PolarLight. This may suggest a variation in the polarization angle related to the source state, which is linked to the variation of corona geometry as reported by IXPE observations of Z sources, or possibly to relativistic precession. |
| title | Sco X-1 as seen by IXPE |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2504.07181 |