Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1
Date Issued
2024
Author(s)
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Poutanen, Juri
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Bianchi, Stefano
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Bobrikova, Anna
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Roberts, Oliver J.
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Romani, Roger W.
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Sgrò, Carmelo
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Slane, Patrick
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Spandre, Gloria
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Swartz, Douglas A.
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Tamagawa, Toru
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Taverna, Roberto
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Deng, Wei
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Tawara, Yuzuru
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Tennant, Allyn F.
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Thomas, Nicholas E.
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Tsygankov, Sergey S.
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Turolla, Roberto
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Vink, Jacco
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Wu, Kinwah
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IXPE Collaboration
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Ge, Ming-Yu
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Jia, Shu-Mei
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Krawczynski, Henric
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Liu, Kuan
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Veledina, Alexandra
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Chen, Wei
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Garcia, Javier A.
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Kaaret, Philip
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Russell, Thomas D.
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Wei, Wen-Hao
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Zhang, Shuang-Nan
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Zuo, Chao
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Arzoumanian, Zaven
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Gnarini, Andrea
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Gendreau, Keith
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Weisskopf, Martin C.
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Zane, Silvia
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Agudo, Iván
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Baldini, Luca
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Baumgartner, Wayne H.
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Bellazzini, Ronaldo
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Bongiorno, Stephen D.
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Bonino, Raffaella
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Brez, Alessandro
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Castellano, Simone
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Cavazzuti, Elisabetta
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Chen, Chien-Ting
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Ciprini, Stefano
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Di Gesu, Laura
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Di Lalla, Niccolò
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Donnarumma, Immacolata
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Doroshenko, Victor
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Dovčiak, Michal
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Ehlert, Steven R.
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Enoto, Teruaki
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Gunji, Shuichi
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Hayashida, Kiyoshi
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Heyl, Jeremy
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Iwakiri, Wataru
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Jorstad, Svetlana G.
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Karas, Vladimir
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Kislat, Fabian
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Kitaguchi, Takao
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Kolodziejczak, Jeffery J.
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Latronico, Luca
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Liodakis, Ioannis
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Maldera, Simone
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Manfreda, Alberto
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Marin, Frédéric
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Marinucci, Andrea
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Marscher, Alan P.
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Marshall, Herman L.
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Mitsuishi, Ikuyuki
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Mizuno, Tsunefumi
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Negro, Michela
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Ng, Chi-Yung
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O'Dell, Stephen L.
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Omodei, Nicola
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Oppedisano, Chiara
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Pavlov, George G.
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Peirson, Abel L.
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Pesce-Rollins, Melissa
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Petrucci, Pierre-Olivier
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Puccetti, Simonetta
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Ramsey, Brian D.
Abstract
The Imaging X-ray Polarimetry Explorer measured with high significance the X-ray polarization of the brightest Z-source, Sco X-1, resulting in the nominal 2-8 keV energy band in a polarization degree of 1.0% ± 0.2% and a polarization angle of 8° ± 6° at a 90% confidence level. This observation was strictly simultaneous with observations performed by NICER, NuSTAR, and Insight-HXMT, which allowed for a precise characterization of its broadband spectrum from soft to hard X-rays. The source has been observed mainly in its soft state, with short periods of flaring. We also observed low-frequency quasiperiodic oscillations. From a spectropolarimetric analysis, we associate a polarization to the accretion disk at <3.2% at 90% confidence level, compatible with expectations for an electron scattering dominated optically thick atmosphere at the Sco X-1 inclination of ~44°; for the higher-energy Comptonized component, we obtain a polarization of 1.3% ± 0.4%, in agreement with expectations for a slab of Thomson optical depth of ~7 and an electron temperature of ~3 keV. A polarization rotation with respect to previous observations by OSO-8 and PolarLight, and also with respect to the radio-jet position angle, is observed. This result may indicate a variation of the polarization with the source state that can be related to relativistic precession or a change in the corona geometry with the accretion flow.
Volume
960
Issue
2
Start page
L11
Issn Identifier
2041-8205
Ads BibCode
2024ApJ...960L..11L
Rights
open.access
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