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

R. Farinelli; S. Fabiani; J. Poutanen; F. Ursini; C. Ferrigno; S. Bianchi; M. Cocchi; F. Capitanio; A. De Rosa; A. Gnarini; F. Kislat; G. Matt; R. Mikusincova; F. Muleri; I. Agudo; L. A. Antonelli; M. Bachetti; L. Baldini; W. H. Baumgartner; R. Bellazzini; S. D. Bongiorno; R. Bonino; A. Brez; N. Bucciantini; S. Castellano; E. Cavazzuti; S. Ciprini; E. Costa; E. Del Monte; L. Di Gesu; N. Di Lalla; A. Di Marco; I. Donnarumma; V. Doroshenko; M. Dovčiak; S. R. Ehlert; T. Enoto; Y. Evangelista; R. Ferrazzoli; J. A. Garcia; S. Gunji; K. Hayashida; J. Heyl; W. Iwakiri; S. G. Jorstad; V. Karas; T. Kitaguchi; J. J. Kolodziejczak; H. Krawczynski; F. La Monaca; L. Latronico; I. Liodakis; S. Maldera; A. Manfreda; F. Marin; A. P. Marscher; H. L. Marshall; I. Mitsuishi; T. Mizuno; C. Y. Ng; S. L. O’Dell; N. Omodei; C. Oppedisano; A. Papitto; G. G. Pavlov; A. L. Peirson; M. Perri; M. Pesce-Rollins; P. O. Petrucci; M. Pilia; A. Possenti; S. Puccetti; B. D. Ramsey; J. Rankin; A. Ratheesh; R. W. Romani; C. Sgrò; P. Slane; P. Soffitta; G. Spandre; T. Tamagawa; F. Tavecchio; R. Taverna; Y. Tawara; A. F. Tennant; N. E. Thomas; F. Tombesi; A. Trois; S. S. Tsygankov; R. Turolla; J. Vink; M. C. Weisskopf; K. Wu; F. Xie; S. Zane

doi:10.1093/mnras/stac3726

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

R. Farinelli, S. Fabiani, J. Poutanen, F. Ursini, C. Ferrigno, S. Bianchi, M. Cocchi, F. Capitanio, A. De Rosa, A. Gnarini, F. Kislat, G. Matt, R. Mikusincova, F. Muleri, I. Agudo, L. A. Antonelli, M. Bachetti, L. Baldini, W. H. Baumgartner, R. BellazziniS. D. Bongiorno, R. Bonino, A. Brez, N. Bucciantini, S. Castellano, E. Cavazzuti, S. Ciprini, E. Costa, E. Del Monte, L. Di Gesu, N. Di Lalla, A. Di Marco, I. Donnarumma, V. Doroshenko, M. Dovčiak, S. R. Ehlert, T. Enoto, Y. Evangelista, R. Ferrazzoli, J. A. Garcia, S. Gunji, K. Hayashida, J. Heyl, W. Iwakiri, S. G. Jorstad, V. Karas, T. Kitaguchi, J. J. Kolodziejczak, H. Krawczynski, F. La Monaca, L. Latronico, I. Liodakis, S. Maldera, A. Manfreda, F. Marin, A. P. Marscher, H. L. Marshall, I. Mitsuishi, T. Mizuno, C. Y. Ng, S. L. O’Dell, N. Omodei, C. Oppedisano, A. Papitto, G. G. Pavlov, A. L. Peirson, M. Perri, M. Pesce-Rollins, P. O. Petrucci, M. Pilia, A. Possenti, S. Puccetti, B. D. Ramsey, J. Rankin, A. Ratheesh, R. W. Romani, C. Sgrò, P. Slane, P. Soffitta, G. Spandre, T. Tamagawa, F. Tavecchio, R. Taverna, Y. Tawara, A. F. Tennant, N. E. Thomas, F. Tombesi, A. Trois, S. S. Tsygankov, R. Turolla, J. Vink, M. C. Weisskopf, K. Wu, F. Xie, S. Zane

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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 kT_in ≈ 1 keV, plus unsaturated Comptonization in thermal plasma with temperature kT_e = 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.

Original language	English (US)
Pages (from-to)	3681-3690
Number of pages	10
Journal	Monthly Notices of the Royal Astronomical Society
Volume	519
Issue number	3
DOIs	https://doi.org/10.1093/mnras/stac3726
State	Published - Mar 1 2023

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

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10.1093/mnras/stac3726

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Farinelli, R., Fabiani, S., Poutanen, J., Ursini, F., Ferrigno, C., Bianchi, S., Cocchi, M., Capitanio, F., De Rosa, A., Gnarini, A., Kislat, F., Matt, G., Mikusincova, R., Muleri, F., Agudo, I., Antonelli, L. A., Bachetti, M., Baldini, L., Baumgartner, W. H., ... Zane, S. (2023). Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements. Monthly Notices of the Royal Astronomical Society, 519(3), 3681-3690. https://doi.org/10.1093/mnras/stac3726

@article{9cd8f297df93458caedb9839b514d5aa,

title = "Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements",

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.",

author = "R. Farinelli and S. Fabiani and J. Poutanen and F. Ursini and C. Ferrigno and S. Bianchi and M. Cocchi and F. Capitanio and {De Rosa}, A. and A. Gnarini and F. Kislat and G. Matt and R. Mikusincova and F. Muleri and I. Agudo and Antonelli, {L. A.} and M. Bachetti and L. Baldini and Baumgartner, {W. H.} and R. Bellazzini and Bongiorno, {S. D.} and R. Bonino and A. Brez and N. Bucciantini and S. Castellano and E. Cavazzuti and S. Ciprini and E. Costa and {Del Monte}, E. and {Di Gesu}, L. and {Di Lalla}, N. and {Di Marco}, A. and I. Donnarumma and V. Doroshenko and M. Dov{\v c}iak and Ehlert, {S. R.} and T. Enoto and Y. Evangelista and R. Ferrazzoli and Garcia, {J. A.} and S. Gunji and K. Hayashida and J. Heyl and W. Iwakiri and Jorstad, {S. G.} and V. Karas and T. Kitaguchi and Kolodziejczak, {J. J.} and H. Krawczynski and {La Monaca}, F. and L. Latronico and I. Liodakis and S. Maldera and A. Manfreda and F. Marin and Marscher, {A. P.} and Marshall, {H. L.} and I. Mitsuishi and T. Mizuno and Ng, {C. Y.} and O{\textquoteright}Dell, {S. L.} and N. Omodei and C. Oppedisano and A. Papitto and Pavlov, {G. G.} and Peirson, {A. L.} and M. Perri and M. Pesce-Rollins and Petrucci, {P. O.} and M. Pilia and A. Possenti and S. Puccetti and Ramsey, {B. D.} and J. Rankin and A. Ratheesh and Romani, {R. W.} and C. Sgr{\`o} and P. Slane and P. Soffitta and G. Spandre and T. Tamagawa and F. Tavecchio and R. Taverna and Y. Tawara and Tennant, {A. F.} and Thomas, {N. E.} and F. Tombesi and A. Trois and Tsygankov, {S. S.} and R. Turolla and J. Vink and Weisskopf, {M. C.} and K. Wu and F. Xie and S. Zane",

note = "Publisher Copyright: {\textcopyright} 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.",

year = "2023",

month = mar,

day = "1",

doi = "10.1093/mnras/stac3726",

language = "English (US)",

volume = "519",

pages = "3681--3690",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

number = "3",

}

Farinelli, R, Fabiani, S, Poutanen, J, Ursini, F, Ferrigno, C, Bianchi, S, Cocchi, M, Capitanio, F, De Rosa, A, Gnarini, A, Kislat, F, Matt, G, Mikusincova, R, Muleri, F, Agudo, I, Antonelli, LA, Bachetti, M, Baldini, L, Baumgartner, WH, Bellazzini, R, Bongiorno, SD, Bonino, R, Brez, A, Bucciantini, N, Castellano, S, Cavazzuti, E, Ciprini, S, Costa, E, Del Monte, E, Di Gesu, L, Di Lalla, N, Di Marco, A, Donnarumma, I, Doroshenko, V, Dovčiak, M, Ehlert, SR, Enoto, T, Evangelista, Y, Ferrazzoli, R, Garcia, JA, Gunji, S, Hayashida, K, Heyl, J, Iwakiri, W, Jorstad, SG, Karas, V, Kitaguchi, T, Kolodziejczak, JJ, Krawczynski, H, La Monaca, F, Latronico, L, Liodakis, I, Maldera, S, Manfreda, A, Marin, F, Marscher, AP, Marshall, HL, Mitsuishi, I, Mizuno, T, Ng, CY, O’Dell, SL, Omodei, N, Oppedisano, C, Papitto, A, Pavlov, GG, Peirson, AL, Perri, M, Pesce-Rollins, M, Petrucci, PO, Pilia, M, Possenti, A, Puccetti, S, Ramsey, BD, Rankin, J, Ratheesh, A, Romani, RW, Sgrò, C, Slane, P, Soffitta, P, Spandre, G, Tamagawa, T, Tavecchio, F, Taverna, R, Tawara, Y, Tennant, AF, Thomas, NE, Tombesi, F, Trois, A, Tsygankov, SS, Turolla, R, Vink, J, Weisskopf, MC, Wu, K, Xie, F & Zane, S 2023, 'Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements', Monthly Notices of the Royal Astronomical Society, vol. 519, no. 3, pp. 3681-3690. https://doi.org/10.1093/mnras/stac3726

TY - JOUR

T1 - Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements

AU - Farinelli, R.

AU - Fabiani, S.

AU - Poutanen, J.

AU - Ursini, F.

AU - Ferrigno, C.

AU - Bianchi, S.

AU - Cocchi, M.

AU - Capitanio, F.

AU - De Rosa, A.

AU - Gnarini, A.

AU - Kislat, F.

AU - Matt, G.

AU - Mikusincova, R.

AU - Muleri, F.

AU - Agudo, I.

AU - Antonelli, L. A.

AU - Bachetti, M.

AU - Baldini, L.

AU - Baumgartner, W. H.

AU - Bellazzini, R.

AU - Bongiorno, S. D.

AU - Bonino, R.

AU - Brez, A.

AU - Bucciantini, N.

AU - Castellano, S.

AU - Cavazzuti, E.

AU - Ciprini, S.

AU - Costa, E.

AU - Del Monte, E.

AU - Di Gesu, L.

AU - Di Lalla, N.

AU - Di Marco, A.

AU - Donnarumma, I.

AU - Doroshenko, V.

AU - Dovčiak, M.

AU - Ehlert, S. R.

AU - Enoto, T.

AU - Evangelista, Y.

AU - Ferrazzoli, R.

AU - Garcia, J. A.

AU - Gunji, S.

AU - Hayashida, K.

AU - Heyl, J.

AU - Iwakiri, W.

AU - Jorstad, S. G.

AU - Karas, V.

AU - Kitaguchi, T.

AU - Kolodziejczak, J. J.

AU - Krawczynski, H.

AU - La Monaca, F.

AU - Latronico, L.

AU - Liodakis, I.

AU - Maldera, S.

AU - Manfreda, A.

AU - Marin, F.

AU - Marscher, A. P.

AU - Marshall, H. L.

AU - Mitsuishi, I.

AU - Mizuno, T.

AU - Ng, C. Y.

AU - O’Dell, S. L.

AU - Omodei, N.

AU - Oppedisano, C.

AU - Papitto, A.

AU - Pavlov, G. G.

AU - Peirson, A. L.

AU - Perri, M.

AU - Pesce-Rollins, M.

AU - Petrucci, P. O.

AU - Pilia, M.

AU - Possenti, A.

AU - Puccetti, S.

AU - Ramsey, B. D.

AU - Rankin, J.

AU - Ratheesh, A.

AU - Romani, R. W.

AU - Sgrò, C.

AU - Slane, P.

AU - Soffitta, P.

AU - Spandre, G.

AU - Tamagawa, T.

AU - Tavecchio, F.

AU - Taverna, R.

AU - Tawara, Y.

AU - Tennant, A. F.

AU - Thomas, N. E.

AU - Tombesi, F.

AU - Trois, A.

AU - Tsygankov, S. S.

AU - Turolla, R.

AU - Vink, J.

AU - Weisskopf, M. C.

AU - Wu, K.

AU - Xie, F.

AU - Zane, S.

PY - 2023/3/1

Y1 - 2023/3/1

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=85148270126&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85148270126&partnerID=8YFLogxK

U2 - 10.1093/mnras/stac3726

DO - 10.1093/mnras/stac3726

M3 - Article

AN - SCOPUS:85148270126

SN - 0035-8711

VL - 519

SP - 3681

EP - 3690

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 3

ER -

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

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