2024ApJ...969L..30S

Query : 2024ApJ...969L..30S

2024ApJ...969L..30S - Astrophys. J., 969, L30 (2024/July-2)

An IXPE-led X-Ray Spectropolarimetric Campaign on the Soft State of Cygnus X-1: X-Ray Polarimetric Evidence for Strong Gravitational Lensing.

STEINER J.F., NATHAN E., HU K., KRAWCZYNSKI H., DOVCIAK M., VELEDINA A., MULERI F., SVOBODA J., ALABARTA K., PARRA M., BHARGAVA Y., MATT G., POUTANEN J., PETRUCCI P.-O., TENNANT A.F., BAGLIO M.C., BALDINI L., BARNIER S., BHATTACHARYYA S., BIANCHI S., BRIGITTE M., CABEZAS M., CANGEMI F., CAPITANIO F., CASEY J., RODRIGUEZ CAVERO N., CASTELLANO S., CAVAZZUTI E., CHUN S., CHURAZOV E., COSTA E., DI LALLA N., DI MARCO A., EGRON E., EWING M., FABIANI S., GARCIA J.A., GREEN D.A., GRINBERG V., HADRAVA P., INGRAM A., KAARET P., KISLAT F., KITAGUCHI T., KRAVTSOV V., KUBATOVA B., LA MONACA F., LATRONICO L., LOKTEV V., MALACARIA C., MARIN F., MARINUCCI A., MARYEVA O., MASTROSERIO G., MIZUNO T., NEGRO M., OMODEI N., PODGORNY J., RANKIN J., RATHEESH A., RHODES L., RUSSELL D.M., SLECHTA M., SOFFITTA P., SPOONER S., SULEIMANOV V., TOMBESI F., TRUSHKIN S.A., WEISSKOPF M.C., ZANE S., ZDZIARSKI A.A., ZHANG S., ZHANG W., ZHOU M., AGUDO I., ANTONELLI L.A., BACHETTI M., BAUMGARTNER W.H., BELLAZZINI R., BONGIORNO S.D., BONINO R., BREZ A., BUCCIANTINI N., CHEN C.-T., CIPRINI S., DE ROSA A., DEL MONTE E., DI GESU L., DONNARUMMA I., DOROSHENKO V., EHLERT S.R., ENOTO T., EVANGELISTA Y., FERRAZZOLI R., GUNJI S., HAYASHIDA K., HEYL J., IWAKIRI W., JORSTAD S.G., KARAS V., KOLODZIEJCZAK J.J., LIODAKIS I., MALDERA S., MANFREDA A., MARSCHER A.P., MARSHALL H.L., MASSARO F., MITSUISHI I., NG C.-Y., O'DELL S.L., OPPEDISANO C., PAPITTO A., PAVLOV G.G., PEIRSON A.L., PERRI M., PESCE-ROLLINS M., PILIA M., POSSENTI A., PUCCETTI S., RAMSEY B.D., ROBERTS O.J., ROMANI R.W., SGRO C., SLANE P., SPANDRE G., SWARTZ D.A., TAMAGAWA T., TAVECCHIO F., TAVERNA R., TAWARA Y., THOMAS N.E., TROIS A., TSYGANKOV S.S., TUROLLA R., VINK J., WU K. and XIE F.

Abstract (from CDS):

We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May-June. Companion multiwavelength data during the campaign are likewise shown. The 2-8 keV X-rays exhibit a net polarization degree PD = 1.99% ± 0.13% (68% confidence). The polarization signal is found to increase with energy across the Imaging X-ray Polarimetry Explorer's (IXPE) 2-8 keV bandpass. The polarized X-rays exhibit an energy-independent polarization angle of PA = -25.°7 ± 1.°8 east of north (68% confidence). This is consistent with being aligned to Cyg X-1's au-scale compact radio jet and its parsec-scale radio lobes. In comparison to earlier hard-state observations, the soft state exhibits a factor of 2 lower polarization degree but a similar trend with energy and a similar (also energy-independent) position angle. When scaling by the natural unit of the disk temperature, we find the appearance of a consistent trend line in the polarization degree between the soft and hard states. Our favored polarimetric model indicates that Cyg X-1's spin is likely high (a* ≳ 0.96). The substantial X-ray polarization in Cyg X-1's soft state is most readily explained as resulting from a large portion of X-rays emitted from the disk returning and reflecting off the disk surface, generating a high polarization degree and a polarization direction parallel to the black hole spin axis and radio jet. In IXPE's bandpass, the polarization signal is dominated by the returning reflection emission. This constitutes polarimetric evidence for strong gravitational lensing of X-rays close to the black hole.

Abstract Copyright: © 2024. The Author(s). Published by the American Astronomical Society.

Journal keyword(s): Accretion - Polarimetry - X-ray astronomy - Stellar mass black holes

Simbad objects: 8

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Number of rows : 8
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 3C 48 QSO 01 37 41.2996631208 +33 09 35.080388820   16.62 16.20     ~ 2924 2
2 X LMC X-3 HXB 05 38 56.6323605504 -64 05 03.317937504   17 17.2     B2.5Ve 722 0
3 X LMC X-1 HXB 05 39 38.8284304464 -69 44 35.531553624   14.8 14.5 14.924   O8(f)p 700 0
4 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4558 2
5 X Nor X-1 LXB 16 34 01.610 -47 23 34.80           ~ 579 0
6 SWIFT J1727.8-1613 HXB 17 27 43.3135483931 -16 12 19.062182343           ~ 140 0
7 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4590 0
8 V* V1408 Aql LXB 19 59 24.0074252040 +11 42 29.859773292 18.40 18.97 18.95 18.70 18.66 ~ 234 0

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