%0 Journal Article
%@ 2041-8205
%A La Monaca, F
%A Di Marco, A
%A Poutanen, J
%A Bachetti, M
%A Motta, SE
%A Papitto, A
%A Pilia, M
%A Xie, F
%A Bianchi, S
%A Bobrikova, A
%A Costa, E
%A Deng, W
%A Ge, MY
%A Illiano, G
%A Jia, SM
%A Krawczynski, H
%A Lai, EV
%A Liu, K
%A Mastroserio, G
%A Muleri, F
%A Rankin, J
%A Soffitta, P
%A Veledina, A
%A Ambrosino, F
%A Del Santo, M
%A Chen, W
%A Garcia, JA
%A Kaaret, P
%A Russell, TD
%A Wei, WH
%A Zhang, SN
%A Zuo, C
%A Arzoumanian, Z
%A Cocchi, M
%A Gnarini, A
%A Farinelli, R
%A Gendreau, K
%A Ursini, F
%A Weisskopf, MC
%A Zane, S
%A Agudo, I
%A Antonelli, LA
%A Baldini, L
%A Baumgartner, WH
%A Bellazzini, R
%A Bongiorno, SD
%A Bonino, R
%A Brez, A
%A Bucciantini, N
%A Capitanio, F
%A Castellano, S
%A Cavazzuti, E
%A Chen, CT
%A Ciprini, S
%A De Rosa, A
%A Del Monte, E
%A Di Gesu, L
%A Di Lalla, N
%A Donnarumma, I
%A Doroshenko, V
%A Dovčiak, M
%A Ehlert, SR
%A Enoto, T
%A Evangelista, Y
%A Fabiani, S
%A Ferrazzoli, R
%A Gunji, S
%A Hayashida, K
%A Heyl, J
%A Iwakiri, W
%A Jorstad, SG
%A Karas, V
%A Kislat, F
%A Kitaguchi, T
%A Kolodziejczak, JJ
%A Latronico, L
%A Liodakis, I
%A Maldera, S
%A Manfreda, A
%A Marin, F
%A Marinucci, A
%A Marscher, AP
%A Marshall, HL
%A Massaro, F
%A Matt, G
%A Mitsuishi, I
%A Mizuno, T
%A Negro, M
%A Ng, CY
%A O’Dell, SL
%A Omodei, N
%A Oppedisano, C
%A Pavlov, GG
%A Peirson, AL
%A Perri, M
%A Pesce-Rollins, M
%A Petrucci, PO
%A Possenti, A
%A Puccetti, S
%A Ramsey, BD
%D 2024
%F discovery:10186104
%J The Astrophysical Journal Letters
%N 2
%T Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1
%U https://discovery.ucl.ac.uk/id/eprint/10186104/
%V 960
%X 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.
%Z Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence, https://creativecommons.org/licenses/by/4.0/. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.