IXPE view of the Sco-like source GX 349+2 in the normal branch

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 mainly found in the normal branch. A model-independe...

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Autores: La Monaca, Fabio, Bobrikova, Anna, Poutanen, Juri, Coti Zelati, Francesco, Pilia, Maura, Veledina, Alexandra, Bachetti, Matteo, Loktev, Vladislav, Xie, Fei
Formato: artículo
Estado:Versión publicada
Fecha de publicación:2025
País:España
Recursos:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/408488
Acesso em linha:http://hdl.handle.net/10261/408488
http://arxiv.org/abs/2507.07163v1
Access Level:acceso abierto
Palavra-chave:Accretion
Accretion disks
Polarization
Stars: individual: GX 349+2
X-rays: binaries
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spelling IXPE view of the Sco-like source GX 349+2 in the normal branchLa Monaca, FabioBobrikova, AnnaPoutanen, JuriCoti Zelati, FrancescoPilia, MauraVeledina, AlexandraBachetti, MatteoLoktev, VladislavXie, FeiAccretionAccretion disksPolarizationStars: individual: GX 349+2X-rays: binariesWe 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 mainly found in the normal branch. A model-independent polarimetric analysis yields a polarisation degree of 1.1%±0.3% at a polarisation angle of 29° ±7° in the 2–8 keV band, with a ∼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 modelling 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, and slightly favour 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 inclinations. A study of the reflection’s polarisation is also reported, with the 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 primarily governed by accretion state and orbital inclination, rather than by the subclass to which the source belongs.This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. This research has made use of the MAXI data provided by RIKEN, JAXA and the MAXI team. The authors acknowledge the NuSTAR team for scheduling the observations. In particular, the authors acknowledge Karl Forster, Daniel Stern, and Fiona A. Harrison. FLM is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-INAF-2022-19-HH.0, by the Istituto Nazionale di Astrofisica (INAF) in Italy, and partially by MAECI with grant CN24GR08 “GRBAXP: Guangxi-Rome Bilateral Agreement for X-ray Polarimetry in Astrophysics”. AB is supported by the Finnish Cultural Foundation grant No. 00240328. AV acknowledges the Academy of Finland grant 355672. Nordita is supported in part by NordForsk. FX is supported by National Key R&D Program of China (grant No. 2023YFE0117200), and National Natural Science Foundation of China (grant No. 12373041 and No. 12422306), and Bagui Scholars Program (XF).Peer reviewedEDP SciencesAgenzia Spaziale ItalianaIstituto Nazionale di AstrofisicaMinistero degli Affari Esteri e della Cooperazione InternazionaleFinnish Cultural FoundationAcademy of FinlandNordForskNational Key Research and Development Program (China)National Natural Science Foundation of ChinaLa Monaca, Fabio [0000-0001-8916-4156]Coti Zelati, Francesco [0000-0001-7611-1581]Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]202520252025info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Publisher's versioninfo:eu-repo/semantics/publishedVersionapplication/pdfhttp://hdl.handle.net/10261/408488http://arxiv.org/abs/2507.07163v1reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Ingléshttps://doi.org/10.1051/0004-6361/202555647Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/4084882026-05-22T06:33:51Z
dc.title.none.fl_str_mv IXPE view of the Sco-like source GX 349+2 in the normal branch
title IXPE view of the Sco-like source GX 349+2 in the normal branch
spellingShingle IXPE view of the Sco-like source GX 349+2 in the normal branch
La Monaca, Fabio
Accretion
Accretion disks
Polarization
Stars: individual: GX 349+2
X-rays: binaries
title_short IXPE view of the Sco-like source GX 349+2 in the normal branch
title_full IXPE view of the Sco-like source GX 349+2 in the normal branch
title_fullStr IXPE view of the Sco-like source GX 349+2 in the normal branch
title_full_unstemmed IXPE view of the Sco-like source GX 349+2 in the normal branch
title_sort IXPE view of the Sco-like source GX 349+2 in the normal branch
dc.creator.none.fl_str_mv La Monaca, Fabio
Bobrikova, Anna
Poutanen, Juri
Coti Zelati, Francesco
Pilia, Maura
Veledina, Alexandra
Bachetti, Matteo
Loktev, Vladislav
Xie, Fei
author La Monaca, Fabio
author_facet La Monaca, Fabio
Bobrikova, Anna
Poutanen, Juri
Coti Zelati, Francesco
Pilia, Maura
Veledina, Alexandra
Bachetti, Matteo
Loktev, Vladislav
Xie, Fei
author_role author
author2 Bobrikova, Anna
Poutanen, Juri
Coti Zelati, Francesco
Pilia, Maura
Veledina, Alexandra
Bachetti, Matteo
Loktev, Vladislav
Xie, Fei
author2_role author
author
author
author
author
author
author
author
dc.contributor.none.fl_str_mv Agenzia Spaziale Italiana
Istituto Nazionale di Astrofisica
Ministero degli Affari Esteri e della Cooperazione Internazionale
Finnish Cultural Foundation
Academy of Finland
NordForsk
National Key Research and Development Program (China)
National Natural Science Foundation of China
La Monaca, Fabio [0000-0001-8916-4156]
Coti Zelati, Francesco [0000-0001-7611-1581]
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Accretion
Accretion disks
Polarization
Stars: individual: GX 349+2
X-rays: binaries
topic Accretion
Accretion disks
Polarization
Stars: individual: GX 349+2
X-rays: binaries
description 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 mainly found in the normal branch. A model-independent polarimetric analysis yields a polarisation degree of 1.1%±0.3% at a polarisation angle of 29° ±7° in the 2–8 keV band, with a ∼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 modelling 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, and slightly favour 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 inclinations. A study of the reflection’s polarisation is also reported, with the 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 primarily governed by accretion state and orbital inclination, rather than by the subclass to which the source belongs.
publishDate 2025
dc.date.none.fl_str_mv 2025
2025
2025
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
Publisher's version
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/408488
http://arxiv.org/abs/2507.07163v1
url http://hdl.handle.net/10261/408488
http://arxiv.org/abs/2507.07163v1
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv https://doi.org/10.1051/0004-6361/202555647
Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv EDP Sciences
publisher.none.fl_str_mv EDP Sciences
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15,81155

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