Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1
Articolo
Data di Pubblicazione:
2024
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.
Tipologia CRIS:
03A-Articolo su Rivista
Elenco autori:
La Monaca F.; Di Marco A.; Poutanen J.; Bachetti M.; Motta S.E.; Papitto A.; Pilia M.; Xie F.; Bianchi S.; Bobrikova A.; Costa E.; Deng W.; Ge M.-Y.; Illiano G.; Jia S.-M.; Krawczynski H.; Lai E.V.; Liu K.; Mastroserio G.; Muleri F.; Rankin J.; Soffitta P.; Veledina A.; Ambrosino F.; Del Santo M.; Chen W.; Garcia J.A.; Kaaret P.; Russell T.D.; Wei W.-H.; Zhang S.-N.; Zuo C.; Arzoumanian Z.; Cocchi M.; Gnarini A.; Farinelli R.; Gendreau K.; Ursini F.; Weisskopf M.C.; Zane S.; Agudo I.; Antonelli L.A.; Baldini L.; Baumgartner W.H.; Bellazzini R.; Bongiorno S.D.; Bonino R.; Brez A.; Bucciantini N.; Capitanio F.; Castellano S.; Cavazzuti E.; Chen C.-T.; Ciprini S.; De Rosa A.; Del Monte E.; Di Gesu L.; Di Lalla N.; Donnarumma I.; Doroshenko V.; Dovciak M.; Ehlert S.R.; Enoto T.; Evangelista Y.; Fabiani S.; Ferrazzoli R.; Gunji S.; Hayashida K.; Heyl J.; Iwakiri W.; Jorstad S.G.; Karas V.; Kislat F.; Kitaguchi T.; Kolodziejczak J.J.; Latronico L.; Liodakis I.; Maldera S.; Manfreda A.; Marin F.; Marinucci A.; Marscher A.P.; Marshall H.L.; Massaro F.; Matt G.; Mitsuishi I.; Mizuno T.; Negro M.; Ng C.-Y.; O'Dell S.L.; Omodei N.; Oppedisano C.; Pavlov G.G.; Peirson A.L.; Perri M.; Pesce-Rollins M.; Petrucci P.-O.; Possenti A.; Puccetti S.; Ramsey B.D.; Ratheesh A.; Roberts O.J.; Romani R.W.; Sgro C.; Slane P.; Spandre G.; Swartz D.A.; Tamagawa T.; Tavecchio F.; Taverna R.; Tawara Y.; Tennant A.F.; Thomas N.E.; Tombesi F.; Trois A.; Tsygankov S.S.; Turolla R.; Vink J.; Wu K.
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