학술논문
Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1
Document Type
Working Paper
Author
La Monaca, Fabio; Di Marco, Alessandro; Poutanen, Juri; Bachetti, Matteo; Motta, Sara E.; Papitto, Alessandro; Pilia, Maura; Xie, Fei; Bianchi, Stefano; Bobrikova, Anna; Costa, Enrico; Deng, Wei; Ge, Mingyu; Illiano, Giulia; Jia, Shu-Mei; Krawczynski, Henric; Lai, Eleonora V.; 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; Zhang, Shuang-Nan; Zuo, Chao; Arzoumanian, Zaven; Cocchi, Massimo; Gnarini, Andrea; Farinelli, Ruben; Gendreau, Keith C.; Ursini, Francesco; Weisskopf, Martin C.; Zane, Silvia; Agudo, Ivan; Antonelli, Lucio Angelo; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolò; Capitanio, Fiamma; Castellano, Simone; Cavazzuti, Elisabetta; Chen, Chien-Ting J.; Ciprini, Stefano; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Di Lalla, Niccolò; Donnarumma, Immacolata; Doroshenko, Victor; Dovciak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Ferrazzoli, Riccardo; Gunji, Shuichi; Hayashidadag, Kiyoshi; Heyl, Jeremy; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kislat, Fabian; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Latronico, Luca; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marin, Fre'de'ric; Marinucci, Andrea; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Matt, Giorgio; Mitsuishi, Ikuyuki; Mizuno, Tsunefumi; Negro, Michela; Ng, Stephen Chi-Yung; O'Dell, Stephen L.; Omodei, Nicola; Oppedisano, Chiara; Pavlov, George; Peirson, Abel L.; Perri, Matteo; Pesce-Rollins, Melissa; Petrucci, Pierre-Olivier; Possenti, Andrea; Puccetti, Simonetta; Ramsey, Brian; Ratheesh, Ajay; Roberts, Oliver J.; Romani, Roger W.; Sgrò, Carmelo; Slane, Patrick; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Vink, Jacco; Wu, Kinwah
Source
ApJL 960 L11 (2024)
Subject
Language
Abstract
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){\deg} 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 <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{\deg}; 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.