2024A&A...691A.216F

Query : 2024A&A...691A.216F

2024A&A...691A.216F - Astronomy and Astrophysics, volume 691A216 (2024/11-1)

Probing the polarized emission from SMC X-1: The brightest X-ray pulsar observed by IXPE.

FORSBLOM S.V., TSYGANKOV S.S., POUTANEN J., DOROSHENKO V., MUSHTUKOV A.A., NG M., RAVI S., MARSHALL H.L., DI MARCO A., LA MONACA F., MALACARIA C., MASTROSERIO G., LOKTEV V., POSSENTI A., SULEIMANOV V.F., TAVERNA R., AGUDO I., ANTONELLI L.A., BACHETTI M., BALDINI L., BAUMGARTNER W.H., BELLAZZINI R., BIANCHI S., BONGIORNO S.D., BONINO R., BREZ A., BUCCIANTINI N., CAPITANIO F., 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., DOVCIAK M., EHLERT S.R., ENOTO T., EVANGELISTA Y., FABIANI S., FERRAZZOLI R., GARCIA J.A., GUNJI S., HAYASHIDA K., HEYL J., IWAKIRI W., JORSTAD S.G., KAARET P., 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., MATT G., 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., 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., TAWARA Y., TENNANT A.F., THOMAS N.E., TOMBESI F., TROIS A., TUROLLA R., VINK J., WEISSKOPF M.C., WU K., XIE F. and ZANE S.

Abstract (from CDS):

Recent observations of X-ray pulsars (XRPs) performed by the Imaging X-ray Polarimetry Explorer (IXPE) have made it possible to investigate the intricate details of these objects in a new way, thanks to the added value of X-ray polarimetry. Here we present the results of the IXPE observations of SMC X-1, a member of the small group of XRPs displaying super-orbital variability. SMC X-1 was observed by IXPE three separate times during the high state of its super-orbital period. The observed luminosity in the 2-8 keV energy band of L ∼ 2 × 1038 erg s–1 makes SMC X-1 the brightest XRP ever observed by IXPE. We detect significant polarization in all three observations, with values of the phase-averaged polarization degree (PD) and polarization angle (PA) of 3.2 ± 0.8% and 97° ±8° for Observation 1, 3.0 ± 0.9% and 90° ±8° for Observation 2, and 5.5 ± 1.1% and 80° ±6° for Observation 3, for the spectro-polarimetric analysis. The observed PD shows an increase over time with decreasing luminosity, while the PA decreases in decrements of ∼10°. The phase-resolved spectro-polarimetric analysis reveals significant detection of polarization in three out of seven phase bins, with the PD ranging between ∼2% and ∼10%, and a corresponding range in the PA from ∼70° to ∼100°. The pulse-phase resolved PD displays an apparent anti-correlation with the flux. Using the rotating vector model, we obtain constraints on the pulsar's geometrical properties for the individual observations. The position angle of the pulsar displays an evolution over time supporting the idea that we observe changes related to different super-orbital phases. Scattering in the wind of the precessing accretion disk may be responsible for the behavior of the polarimetric properties observed during the high-state of SMC X-1's super-orbital period.

Abstract Copyright: © The Authors 2024

Journal keyword(s): accretion, accretion disks - magnetic fields - polarization - stars: neutron - pulsars: individual: SMC X-1 - X-rays: binaries

Simbad objects: 12

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Number of rows : 12
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 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 12317 1
2 SK 160 HXB 01 17 05.1457288392 -73 26 36.014808156 12.23 13.00 13.15   13.17 O9.7Ia+ 918 0
3 SWIFT J0243.6+6124 HXB 02 43 40.4252869512 +61 26 03.757456824   13.71 12.84 12.57   O9.5Ve 208 0
4 V* X Per HXB 03 55 23.0777456088 +31 02 45.039836148 6.090 6.840 6.720     O9.5III 1037 0
5 LS V +44 17 HXB 04 40 59.3296237272 +44 31 49.258049376 11.02 11.42 10.73 10.28 9.76 B0.2Ve 176 0
6 V* GP Vel HXB 09 02 06.8608812864 -40 33 16.899168060 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1588 0
7 GRO J1008-571 HXB 10 09 46.9642314696 -58 17 35.603851848       14.63   B0e 269 0
8 V* V779 Cen HXB 11 21 15.0920532528 -60 37 25.630264596   14.4 12.27     O9III/Veq 1159 0
9 V* BP Cru HXB 12 26 37.5605188992 -62 46 13.261044684   12.482 10.803 10.304   B1Ia+ 731 0
10 V* KZ TrA LXB 16 32 16.79 -67 27 39.3 17.40 18.60 18.5     ~ 626 1
11 V* HZ Her LXB 16 57 49.8110126616 +35 20 32.486555472 11.90 14.89 13.63 13.88   B3/6ep 2172 0
12 V* V2246 Cyg HXB 20 32 15.2749858128 +37 38 14.843024844   22.16 19.41 17.32 15.18 B0Ve 480 0

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