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Title: | Discovery of a strong rotation of the X-ray polarization angle in the galactic burster GX 13+1 | Authors: | Bobrikova, Anna Forsblom, Sofia V. DI MARCO, Alessandro LA MONACA, Fabio Poutanen, Juri Ng, Mason Ravi, Swati Loktev, Vladislav Kajava, Jari J. E. Ursini, Francesco Veledina, Alexandra Rogantini, Daniele Salmi, Tuomo Bianchi, Stefano CAPITANIO, FIAMMA Done, Chris FABIANI, Sergio Gnarini, Andrea Heyl, Jeremy Kaaret, Philip Matt, Giorgio MULERI, FABIO Nitindala, Anagha P. RANKIN, John Weisskopf, Martin C. Agudo, Iván ANTONELLI, Lucio Angelo BACHETTI, Matteo Baldini, Luca Baumgartner, Wayne H. Bellazzini, Ronaldo Bongiorno, Stephen D. Bonino, Raffaella Brez, Alessandro BUCCIANTINI, Niccolo' Castellano, Simone Cavazzuti, Elisabetta Chen, Chien-Ting Ciprini, Stefano COSTA, ENRICO DE ROSA, Alessandra DEL MONTE, Ettore Di Gesu, Laura Di Lalla, Niccolò Donnarumma, Immacolata Doroshenko, Victor Dovčiak, Michal Ehlert, Steven R. Enoto, Teruaki EVANGELISTA, YURI FERRAZZOLI, Riccardo García, Javier A. Gunji, Shuichi Hayashida, Kiyoshi Iwakiri, Wataru Jorstad, Svetlana G. Karas, Vladimir Kislat, Fabian Kitaguchi, Takao Kolodziejczak, Jeffery J. Krawczynski, Henric Latronico, Luca Liodakis, Ioannis Maldera, Simone Manfreda, Alberto Marin, Frédéric Marinucci, Andrea Marscher, Alan P. Marshall, Herman L. MASSARO, FRANCESCO Mitsuishi, Ikuyuki Mizuno, Tsunefumi Negro, Michela Ng, Chi-Yung O'Dell, Stephen L. Omodei, Nicola Oppedisano, Chiara PAPITTO, ALESSANDRO Pavlov, George G. Peirson, Abel L. PERRI, Matteo Pesce-Rollins, Melissa Petrucci, Pierre-Olivier PILIA, Maura POSSENTI, ANDREA Puccetti, Simonetta Ramsey, Brian D. RATHEESH, AJAY Roberts, Oliver J. Romani, Roger W. Sgrò, Carmelo Slane, Patrick SOFFITTA, PAOLO Spandre, Gloria Swartz, Douglas A. Tamagawa, Toru TAVECCHIO, Fabrizio Taverna, Roberto Tawara, Yuzuru Tennant, Allyn F. Thomas, Nicholas E. TOMBESI, Francesco TROIS, ALESSIO Tsygankov, Sergey S. Turolla, Roberto Vink, Jacco Wu, Kinwah XIE, FEI Zane, Silvia |
Issue Date: | 2024 | Journal: | ASTRONOMY & ASTROPHYSICS | Number: | 688 | First Page: | A170 | Abstract: | Weakly magnetized neutron stars in X-ray binaries show a complex phenomenology with several spectral components that can be associated with the accretion disk, the boundary, and/or a spreading layer, a corona, and a wind. Spectroscopic information alone, however, is not enough to distinguish these components. The analysis of the timing data revealed that most of the variability, and in particular, kilohertz quasi-period oscillations, are associated with the high-energy component that corresponds to the boundary and/or spreading layer. Additional information about the nature of the spectral components, and in particular, about the geometry of the emission region, can be provided by X-ray polarimetry. One of the objects of the class, a bright, persistent, and rather peculiar galactic Type I X-ray burster GX 13+1, was observed with the Imaging X-ray Polarimetry Explorer (IXPE) and the XMM-Newton. Using the XMM-Newton data, we obtained the best-fit values for the continuum spectral parameters and detected strong absorption lines associated with the accretion disk wind. IXPE data showed the source to be significantly polarized in the 2-8 keV energy band, with an overall polarization degree (PD) of 1.4%±0.3% at a polarization angle (PA) of −2° ±6° (errors at the 68% confidence level). During the two-day long observation, we detected rotation of the PA by about 70° with the corresponding changes in the PD from 2% to nondetectable and then up to 5%. These variations in polarization properties are not accompanied by visible spectral state changes of the source. The energy-resolved polarimetric analysis showed a significant change in polarization, from being strongly dependent on energy at the beginning of the observation to being almost constant with energy in the later parts of the observation. As a possible interpretation, we suggest a constant polarization component, strong wind scattering, or a different polarization of the two main spectral components with an individually peculiar behavior. The rotation of the PA suggests a misalignment of the neutron star spin from the orbital axis. | URI: | http://hdl.handle.net/20.500.12386/35664 | URL: | http://arxiv.org/abs/2401.13058v2 https://www.aanda.org/articles/aa/full_html/2024/08/aa49318-24/aa49318-24.html |
ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/202449318 | Bibcode ADS: | 2024A&A...688A.170B | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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