IXPE view of the Sco-like source GX 349+2 in the normal branch
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arXiv
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| Natura: | Preprint |
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2025
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| author | La Monaca, Fabio Bobrikova, Anna Poutanen, Juri Zelati, Francesco Coti Pilia, Maura Veledina, Alexandra Bachetti, Matteo Loktev, Vladislav Xie, Fei |
| author_facet | La Monaca, Fabio Bobrikova, Anna Poutanen, Juri Zelati, Francesco Coti Pilia, Maura Veledina, Alexandra Bachetti, Matteo Loktev, Vladislav Xie, Fei |
| contents | We present a detailed spectropolarimetric study of the Sco-like Z-source GX 349+2, simultaneously observed with the Imaging X-ray Polarimetry Explorer (IXPE) and Nuclear Spectroscopic Telescope Array (NuSTAR). During the observations GX 349+2 was found mainly in the normal branch. A model-independent polarimetric analysis yields a polarisation degree of $1.1\% \pm 0.3\%$ at a polarisation angle of $29° \pm 7°$ in the 2--8 keV band, with ${\sim}4.1σ$ confidence level significance. No variability of polarisation in time and flux has been observed, while an energy-resolved analysis shows a complex dependence of polarisation on energy, as confirmed by a spectropolarimetric analysis. Spectral modeling reveals a dominant disc blackbody component and a Comptonising emitting region, with evidence of a broad iron line associated with a reflection component. Spectropolarimetric fits suggest differing polarisation properties for the disc and Comptonised components, slightly favouring a spreading layer geometry. The polarisation of the Comptonised component exceeds the theoretical expectations, but is in line with the results for other Z-sources with similar inclination. A study of the reflection's polarisation is also reported, with polarisation degree ranging around 10% depending on the assumptions. Despite GX 349+2's classification as a Sco-like source, these polarimetric results align more closely with the Cyg-like system GX 340+0 of similar inclination. This indicates that polarisation is governed primarily by accretion state and orbital inclination, rather than by the subclass to which the source belongs. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_07163 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | IXPE view of the Sco-like source GX 349+2 in the normal branch La Monaca, Fabio Bobrikova, Anna Poutanen, Juri Zelati, Francesco Coti Pilia, Maura Veledina, Alexandra Bachetti, Matteo Loktev, Vladislav Xie, Fei High Energy Astrophysical Phenomena We present a detailed spectropolarimetric study of the Sco-like Z-source GX 349+2, simultaneously observed with the Imaging X-ray Polarimetry Explorer (IXPE) and Nuclear Spectroscopic Telescope Array (NuSTAR). During the observations GX 349+2 was found mainly in the normal branch. A model-independent polarimetric analysis yields a polarisation degree of $1.1\% \pm 0.3\%$ at a polarisation angle of $29° \pm 7°$ in the 2--8 keV band, with ${\sim}4.1σ$ confidence level significance. No variability of polarisation in time and flux has been observed, while an energy-resolved analysis shows a complex dependence of polarisation on energy, as confirmed by a spectropolarimetric analysis. Spectral modeling reveals a dominant disc blackbody component and a Comptonising emitting region, with evidence of a broad iron line associated with a reflection component. Spectropolarimetric fits suggest differing polarisation properties for the disc and Comptonised components, slightly favouring a spreading layer geometry. The polarisation of the Comptonised component exceeds the theoretical expectations, but is in line with the results for other Z-sources with similar inclination. A study of the reflection's polarisation is also reported, with polarisation degree ranging around 10% depending on the assumptions. Despite GX 349+2's classification as a Sco-like source, these polarimetric results align more closely with the Cyg-like system GX 340+0 of similar inclination. This indicates that polarisation is governed primarily by accretion state and orbital inclination, rather than by the subclass to which the source belongs. |
| title | IXPE view of the Sco-like source GX 349+2 in the normal branch |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2507.07163 |