Data di Pubblicazione:
2023
Abstract:
This paper reports the first detection of polarization in the X-rays for atoll-source 4U 1820−303, obtained with the Imaging X-ray Polarimetry Explorer (IXPE) at 99.999% confidence level (CL). Simultaneous polarimetric measurements were also performed in the radio with the Australia Telescope Compact Array. The IXPE observations of 4U 1820−303 were coordinated with Swift X-ray Telescope, Neutron Star Interior Composition Explorer, and Nuclear Spectroscopic Telescope Array aiming to obtain an accurate X-ray spectral model covering a broad energy interval. The source shows a significant polarization above 4 keV, with a polarization degree of 2.0% ± 0.5% and a polarization angle of −55° ± 7° in the 4-7 keV energy range, and a polarization degree of 10% ± 2% and a polarization angle of −67° ± 7° in the 7-8 keV energy bin. This polarization also shows a clear energy trend with polarization degree increasing with energy and a hint for a position-angle change of ≃90° at 96% CL around 4 keV. The spectro-polarimetric fit indicates that the accretion disk is polarized orthogonally to the hard spectral component, which is presumably produced in the boundary/spreading layer. We do not detect linear polarization from the radio counterpart, with a 3σ upper limit of 50% at 7.25 GHz.
Tipologia CRIS:
03A-Articolo su Rivista
Elenco autori:
Di Marco A.; La Monaca F.; Poutanen J.; Russell T.D.; Anitra A.; Farinelli R.; Mastroserio G.; Muleri F.; Xie F.; Bachetti M.; Burderi L.; Carotenuto F.; Del Santo M.; Di Salvo T.; Dovciak M.; Gnarini A.; Iaria R.; Kajava J.J.E.; Liu K.; Middei R.; O'Dell S.L.; Pilia M.; Rankin J.; Sanna A.; Eijnden J.V.D.; Weisskopf M.C.; Bobrikova A.; Capitanio F.; Costa E.; Kaaret P.; Marino A.; Soffitta P.; Ursini F.; Ambrosino F.; Cocchi M.; Fabiani S.; Marshall H.L.; Matt G.; Motta S.E.; Papitto A.; Stella L.; Tarana A.; Zane S.; Agudo I.; Antonelli L.A.; Baldini L.; Baumgartner W.H.; Bellazzini R.; Bianchi S.; Bongiorno S.D.; Bonino R.; Brez A.; Bucciantini N.; 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.; Ehlert S.R.; Enoto T.; Evangelista Y.; Ferrazzoli R.; Garcia J.A.; Gunji S.; Hayashida K.; Heyl J.; Iwakiri W.; Jorstad S.G.; Karas V.; Kislat F.; Kitaguchi T.; Kolodziejczak J.J.; Krawczynski H.; Latronico L.; Liodakis I.; Maldera S.; Manfreda A.; Marin F.; Marinucci A.; Marscher A.P.; Massaro F.; Mitsuishi I.; Mizuno T.; Negro M.; Ng C.-Y.; 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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