2023MNRAS.519.3681F

Query : 2023MNRAS.519.3681F

2023MNRAS.519.3681F - Mon. Not. R. Astron. Soc., 519, 3681-3690 (2023/March-1)

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

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., BELLAZZINI R., BONGIORNO S.D., 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., 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., KITAGUCHI T., KOLODZIEJCZAK J.J., KRAWCZYNSKI H., LA MONACA F., LATRONICO L., LIODAKIS I., MALDERA S., MANFREDA A., MARIN F., MARSCHER A.P., MARSHALL H.L., MITSUISHI I., MIZUNO T., 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., POSSENTI A., PUCCETTI S., RAMSEY B.D., RANKIN J., RATHEESH A., ROMANI R.W., SGRO C., SLANE P., SOFFITTA P., SPANDRE G., 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. and ZANE S.

Abstract (from CDS):

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.

Abstract Copyright: © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society

Journal keyword(s): accretion, accretion discs - polarization - techniques: polarimetric - stars: neutron - X-rays: binaries - X-rays: individual: Cyg X-2

Simbad objects: 6

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Number of rows : 6
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 V* V818 Sco LXB 16 19 55.0692669024 -15 38 25.017666540 11.60 12.40 11.1     Oev 1730 0
2 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4590 0
3 V* V2246 Cyg HXB 20 32 15.2749858128 +37 38 14.843024844   22.16 19.41 17.32 15.18 B0Ve 480 0
4 V* V1521 Cyg HXB 20 32 25.78 +40 57 27.9           WN4/5-6/7 2035 2
5 V* SS Cyg CV* 21 42 42.8034497592 +43 35 09.867842484 11.07 12.651 12.032 9.326   K5V 1324 1
6 V* V1341 Cyg LXB 21 44 41.1544345272 +38 19 17.066570988 15.00 15.13 14.68 15.00   A9III 1229 1

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