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Article: Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements

TitleAccretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements
Authors
Issue Date20-Dec-2022
PublisherRoyal Astronomical Society
Citation
Monthly Notices of the Royal Astronomical Society, 2022, v. 519, n. 3, p. 3681-3690 How to Cite?
Abstract

We report spectro-polarimetric results of an observational campaign of the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER, and INTEGRAL. Consistently with previous results, the broad-band spectrum is characterized by a lower-energy component, attributed to the accretion disc with kTin ≈ 1 keV, plus unsaturated Comptonization in thermal plasma with temperature kTe = 3 keV and optical depth τ ≈ 4, assuming a slab geometry. We measure the polarization degree in the 2–8 keV band P = 1.8 ± 0.3 per cent and polarization angle ϕ = 140° ± 4°, consistent with the previous X-ray polarimetric measurements by OSO-8 as well as with the direction of the radio jet which was earlier observed from the source. While polarization of the disc spectral component is poorly constrained with the IXPE data, the Comptonized emission has a polarization degree P = 4.0 ± 0.7 per cent and a polarization angle aligned with the radio jet. Our results strongly favour a spreading layer at the neutron star surface as the main source of the polarization signal. However, we cannot exclude a significant contribution from reflection off the accretion disc, as indicated by the presence of the iron fluorescence line.


Persistent Identifierhttp://hdl.handle.net/10722/331185
ISSN
2023 Impact Factor: 4.7
2023 SCImago Journal Rankings: 1.621

 

DC FieldValueLanguage
dc.contributor.authorFarinelli, R-
dc.contributor.authorFabiani, S-
dc.contributor.authorPoutanen, J-
dc.contributor.authorUrsini, F-
dc.contributor.authorFerrigno, C-
dc.contributor.authorBianchi, S-
dc.contributor.authorCocchi, M-
dc.contributor.authorCapitanio, F-
dc.contributor.authorDe Rosa, A-
dc.contributor.authorGnarini, A-
dc.contributor.authorKislat, F-
dc.contributor.authorMatt, G-
dc.contributor.authorMikusincova, R-
dc.contributor.authorMuleri, F-
dc.contributor.authorAgudo, I-
dc.contributor.authorAntonelli, LA-
dc.contributor.authorBachetti, M-
dc.contributor.authorBaldini, L-
dc.contributor.authorBaumgartner, WH-
dc.contributor.authorBellazzini, R-
dc.contributor.authorBongiorno, SD-
dc.contributor.authorBonino, R-
dc.contributor.authorBrez, A-
dc.contributor.authorBucciantini, N-
dc.contributor.authorCastellano, S-
dc.contributor.authorCavazzuti, E-
dc.contributor.authorCiprini, S-
dc.contributor.authorCosta, E-
dc.contributor.authorDel Monte, E-
dc.contributor.authorDi Gesu, L-
dc.contributor.authorDi Lalla, N-
dc.contributor.authorDi Marco, A-
dc.contributor.authorDonnarumma, I-
dc.contributor.authorDoroshenko, V-
dc.contributor.authorDovciak, M-
dc.contributor.authorEhlert, SR-
dc.contributor.authorEnoto, T-
dc.contributor.authorEvangelista, Y-
dc.contributor.authorFerrazzoli, R-
dc.contributor.authorGarcia, JA-
dc.contributor.authorGunji, S-
dc.contributor.authorHayashida, K-
dc.contributor.authorHeyl, J-
dc.contributor.authorIwakiri, W-
dc.contributor.authorJorstad, SG-
dc.contributor.authorKaras, V-
dc.contributor.authorKitaguchi, T-
dc.contributor.authorKolodziejczak, JJ-
dc.contributor.authorKrawczynski, H-
dc.contributor.authorLa Monaca, F-
dc.contributor.authorLatronico, L-
dc.contributor.authorLiodakis, I-
dc.contributor.authorMaldera, S-
dc.contributor.authorManfreda, A-
dc.contributor.authorMarin, F-
dc.contributor.authorMarscher, AP-
dc.contributor.authorMarshall, HL-
dc.contributor.authorMitsuishi, I-
dc.contributor.authorMizuno, T-
dc.contributor.authorNg, CY-
dc.contributor.authorO'Dell, SL-
dc.contributor.authorOmodei, N-
dc.contributor.authorOppedisano, C-
dc.contributor.authorPapitto, A-
dc.contributor.authorPavlov, GG-
dc.contributor.authorPeirson, AL-
dc.contributor.authorPerri, M-
dc.contributor.authorPesce-Rollins, M-
dc.contributor.authorPetrucci, PO-
dc.contributor.authorPilia, M-
dc.contributor.authorPossenti, A-
dc.contributor.authorPuccetti, S-
dc.contributor.authorRamsey, BD-
dc.contributor.authorRankin, J-
dc.contributor.authorRatheesh, A-
dc.contributor.authorRomani, RW-
dc.contributor.authorSgro, C-
dc.contributor.authorSlane, P-
dc.contributor.authorSoffitta, P-
dc.contributor.authorSpandre, G-
dc.contributor.authorTamagawa, T-
dc.contributor.authorTavecchio, F-
dc.contributor.authorTaverna, R-
dc.contributor.authorTawara, Y-
dc.contributor.authorTennant, AF-
dc.contributor.authorThomas, NE-
dc.contributor.authorTombesi, F-
dc.contributor.authorTrois, A-
dc.contributor.authorTsygankov, SS-
dc.contributor.authorTurolla, R-
dc.contributor.authorVink, J-
dc.contributor.authorWeisskopf, MC-
dc.contributor.authorWu, K-
dc.contributor.authorXie, F-
dc.contributor.authorZane, S-
dc.date.accessioned2023-09-21T06:53:29Z-
dc.date.available2023-09-21T06:53:29Z-
dc.date.issued2022-12-20-
dc.identifier.citationMonthly Notices of the Royal Astronomical Society, 2022, v. 519, n. 3, p. 3681-3690-
dc.identifier.issn0035-8711-
dc.identifier.urihttp://hdl.handle.net/10722/331185-
dc.description.abstract<p>We report spectro-polarimetric results of an observational campaign of the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by <em>IXPE, NICER</em>, and <em>INTEGRAL</em>. Consistently with previous results, the broad-band spectrum is characterized by a lower-energy component, attributed to the accretion disc with <em>kT</em><sub>in</sub> ≈ 1 keV, plus unsaturated Comptonization in thermal plasma with temperature <em>kT</em><sub>e</sub> = 3 keV and optical depth τ ≈ 4, assuming a slab geometry. We measure the polarization degree in the 2–8 keV band <em>P</em> = 1.8 ± 0.3 per cent and polarization angle ϕ = 140° ± 4°, consistent with the previous X-ray polarimetric measurements by <em>OSO-8</em> as well as with the direction of the radio jet which was earlier observed from the source. While polarization of the disc spectral component is poorly constrained with the <em>IXPE</em> data, the Comptonized emission has a polarization degree <em>P</em> = 4.0 ± 0.7 per cent and a polarization angle aligned with the radio jet. Our results strongly favour a spreading layer at the neutron star surface as the main source of the polarization signal. However, we cannot exclude a significant contribution from reflection off the accretion disc, as indicated by the presence of the iron fluorescence line.<br></p>-
dc.languageeng-
dc.publisherRoyal Astronomical Society-
dc.relation.ispartofMonthly Notices of the Royal Astronomical Society-
dc.titleAccretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements-
dc.typeArticle-
dc.identifier.doi10.1093/mnras/stac3726-
dc.identifier.volume519-
dc.identifier.issue3-
dc.identifier.spage3681-
dc.identifier.epage3690-
dc.identifier.eissn1365-2966-
dc.identifier.issnl0035-8711-

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