Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1
Creators: name: La Monaca, Fabio
name: Di Marco, Alessandro
name: Poutanen, Juri
name: Bachetti, Matteo
name: Motta, Sara E.
name: Papitto, Alessandro
name: Pilia, Maura
name: Xie, Fei
name: Bianchi, Stefano
name: Bobrikova, Anna
name: Costa, Enrico
name: Deng, Wei
name: Ge, Mingyu
name: Illiano, Giulia
name: Jia, Shu-Mei
name: Krawczynski, Henric
name: Lai, Eleonora V.
name: Liu, Kuan
name: Mastroserio, Guglielmo
name: Muleri, Fabio
name: Rankin, John
name: Soffitta, Paolo
name: Veledina, Alexandra
name: Ambrosino, Filippo
name: Del Santo, Melania
name: Chen, Wei
name: Garcia, Javier A.
name: Kaaret, Philip
name: Russell, Thomas D.
name: Wei, Wen-Hao
name: Zhang, Shuang-Nan
name: Zuo, Chao
name: Arzoumanian, Zaven
name: Cocchi, Massimo
name: Gnarini, Andrea
name: Farinelli, Ruben
name: Gendreau, Keith C.
name: Ursini, Francesco
name: Weisskopf, Martin C.
name: Zane, Silvia
name: Agudo, Ivan
name: Antonelli, Lucio Angelo
name: Baldini, Luca
name: Baumgartner, Wayne H.
name: Bellazzini, Ronaldo
name: Bongiorno, Stephen D.
name: Bonino, Raffaella
name: Brez, Alessandro
name: Bucciantini, Niccolò
name: Capitanio, Fiamma
name: Castellano, Simone
name: Cavazzuti, Elisabetta
name: Chen, Chien-Ting J.
name: Ciprini, Stefano
name: De Rosa, Alessandra
name: Del Monte, Ettore
name: Di Gesu, Laura
name: Di Lalla, Niccolò
name: Donnarumma, Immacolata
name: Doroshenko, Victor
name: Dovciak, Michal
name: Ehlert, Steven R.
name: Enoto, Teruaki
name: Evangelista, Yuri
name: Fabiani, Sergio
name: Ferrazzoli, Riccardo
name: Gunji, Shuichi
name: Hayashidadag, Kiyoshi
name: Heyl, Jeremy
name: Iwakiri, Wataru
name: Jorstad, Svetlana G.
name: Karas, Vladimir
name: Kislat, Fabian
name: Kitaguchi, Takao
name: Kolodziejczak, Jeffery J.
name: Latronico, Luca
name: Liodakis, Ioannis
name: Maldera, Simone
name: Manfreda, Alberto
name: Marin, Fre'de'ric
name: Marinucci, Andrea
name: Marscher, Alan P.
name: Marshall, Herman L.
name: Massaro, Francesco
name: Matt, Giorgio
name: Mitsuishi, Ikuyuki
name: Mizuno, Tsunefumi
name: Negro, Michela
name: Ng, Stephen Chi-Yung
name: O'Dell, Stephen L.
name: Omodei, Nicola
name: Oppedisano, Chiara
name: Pavlov, George
name: Peirson, Abel L.
name: Perri, Matteo
name: Pesce-Rollins, Melissa
name: Petrucci, Pierre-Olivier
name: Possenti, Andrea
name: Puccetti, Simonetta
name: Ramsey, Brian
name: Ratheesh, Ajay
name: Roberts, Oliver J.
name: Romani, Roger W.
name: Sgrò, Carmelo
name: Slane, Patrick
name: Spandre, Gloria
name: Swartz, Douglas A.
name: Tamagawa, Toru
name: Tavecchio, Fabrizio
name: Taverna, Roberto
name: Tawara, Yuzuru
name: Tennant, Allyn F.
name: Thomas, Nicholas
name: Tombesi, Francesco
name: Trois, Alessio
name: Tsygankov, Sergey S.
name: Turolla, Roberto
name: Vink, Jacco
name: Wu, Kinwah
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The Imaging X-ray Polarimetry Explorer (IXPE) measured with high significance the X-ray polarization of the brightest Z-source Scorpius 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 90% of confidence level. This observation was strictly simultaneous with observations performed by NICER, NuSTAR, and Insight-HXMT, which allowed for a precise characterization of its broad-band 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 quasi-periodic oscillations. From a spectro-polarimetric analysis, we associate a polarization to the accretion disk at &lt;3.2% at 90% of 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 to a change in the corona geometry with the accretion flow.