X-ray polarimetry and spectroscopy of the neutron star low-mass X-ray binary GX 9+9: An in-depth study with IXPE and NuSTAR
Articolo
Data di Pubblicazione:
2023
Abstract:
We report on a comprehensive analysis of simultaneous X-ray polarimetric and spectral data of the bright atoll source GX 9+9 with the Imaging X-ray Polarimetry Explorer (IXPE) and NuSTAR. The source is significantly polarized in the 4- 8 keV band, with a degree of 2.2% ± 0.5% (uncertainty at the 68% confidence level). The NuSTAR broad-band spectrum clearly shows an iron line, and is well described by a model including thermal disc emission, a Comptonized component, and reflection. From a spectro-polarimetric fit, we obtain an upper limit to the polarization degree of the disc of 4% (at the 99% confidence level), while the contribution of Comptonized and reflected radiation cannot be conclusively separated. However, the polarization is consistent with resulting from a combination of Comptonization in a boundary or spreading layer, plus reflection off the disc, which significantly contributes in any realistic scenario.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
Accretion; Accretion disks; Polarization; Stars: neutron; X-rays: binaries; X-rays: general; X-rays: individuals: GX 9+9
Elenco autori:
Ursini F.; Farinelli R.; Gnarini A.; Poutanen J.; Bianchi S.; Capitanio F.; Di Marco A.; Fabiani S.; La Monaca F.; Malacaria C.; Matt G.; Mikusincova R.; Cocchi M.; Kaaret P.; Kajava J.J.E.; Pilia M.; Zhang W.; Agudo I.; Antonelli L.A.; Bachetti M.; Baldini L.; Baumgartner W.H.; Bellazzini R.; Bongiorno S.D.; Bonino R.; Brez A.; Bucciantini N.; Castellano S.; Cavazzuti E.; Chen C.-T.; Ciprini S.; Costa E.; 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.; 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.; Marshall H.L.; Massaro F.; Mitsuishi I.; Mizuno T.; Muleri F.; Negro M.; Ng C.-Y.; O'Dell S.L.; Omodei N.; Oppedisano C.; Papitto A.; Pavlov G.G.; Peirson A.L.; Perri M.; Pesce-Rollins M.; Petrucci P.-O.; Pilia M.; Posenti A.; Puccetti S.; Ramsey B.D.; Rankin J.; Ratheesh A.; Roberts O.J.; Romani R.W.; Sgro C.; Slane P.; Soffitta 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.; Weisskopf M.C.; Wu K.; Xie F.; Zane S.
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