Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1

• Published in: Astrophysical journal. Letters 2024-01, Vol.960 (2), p.L11
• Main Authors: La Monaca, Fabio, Di Marco, Alessandro, Poutanen, Juri, Bachetti, Matteo, Motta, Sara Elisa, Pilia, Maura, Xie, Fei, Bobrikova, Anna, Costa, Enrico, Deng, Wei, Illiano, Giulia, Jia, Shu-Mei, Krawczynski, Henric, Lai, Eleonora Veronica, Liu, Kuan, Mastroserio, Guglielmo, Muleri, Fabio, Rankin, John, Soffitta, Paolo, Veledina, Alexandra, Ambrosino, Filippo, Del Santo, Melania, Chen, Wei, Garcia, Javier A., Kaaret, Philip, Russell, Thomas D., Wei, Wen-Hao, Zuo, Chao, Arzoumanian, Zaven, Cocchi, Massimo, Gnarini, Andrea, Farinelli, Ruben, Gendreau, Keith, Ursini, Francesco, Weisskopf, Martin C., Zane, Silvia, Agudo, Iván, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolò, Donnarumma, Immacolata, Ehlert, Steven R., Evangelista, Yuri, Fabiani, Sergio, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., 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, Pavlov, George G., Peirson, Abel L., Pesce-Rollins, Melissa, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, 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
• Format: Article
• Language: English
• Subjects: Accretion; Accretion disks; Astrophysics; Broadband; Confidence intervals; Corona; Electron energy; Energy bands; Hard X-rays; Low-mass x-ray binary stars; Neutron stars; Optical analysis; Optical thickness; Polarimetry; Polarization; Radio jets (astronomy); Sciences of the Universe; Spectropolarimetry; Stellar accretion disks; X ray imagery; X-ray telescopes; X-rays
• ISSN: 2041-8205; 0004-637X; 2041-8213; 2041-8213; 1538-4357
• DOI: 10.3847/2041-8213/ad132d

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