![]() Plasma ejection from magnetic flares and the X-ray spectrum of Cygnus X-1. X-ray polarization from accreting black holes: coronal emission. Polarization in lamp-post model of black-hole accretion discs. Light-bending scenario for accreting black holes in X-ray polarimetry. Radiative Transfer (Dover Publications, New York, 1960).ĭovciak, M., Muleri, F., Goosmann, R. The soft state of Cygnus X-1 observed with NuSTAR: a variable corona and a stable inner disk. The trigonometric parallax of Cygnus X-1. A transient relativistic radio jet from Cygnus X-1. ![]() A relativistic jet from Cygnus X-1 in the low/hard X-ray state. Calibration and performance studies of the balloon-borne hard X-ray polarimeter PoGO+. Spectrum and polarization of X-rays from accretion disks around black holes. Analysis of NuSTAR and Suzaku observations of Cyg X-1 in the hard state: evidence for a truncated disc geometry. Spectral and temporal behavior of the black hole candidate XTE J1118+480 as observed with BeppoSAX. A light bending model for the X-ray temporal and spectral properties of accreting black holes. Cygnus X-1-a spectroscopic binary with a heavy companion? Nature 235, 37–28 (1972). On the determination of the spin of the black hole in Cyg X-1 from X-ray reflection spectra. Suzaku results on Cygnus X-1 in the low/hard state. When considered together with existing spectral and timing data, our result reveals that the accretion corona is either an extended structure, or is located far from the black hole in the hard state of Cygnus X-1. The low polarization fraction, <8.6% (upper limit at a 90% confidence level), and the alignment of the polarization angle with the jet axis show that the dominant emission is not influenced by strong gravity. Here, we report observational results on the linear polarization of hard X-ray emission (19–181 keV) from a BHB, Cygnus X-1 4, in the hard state. The extent of the corona differs between the two models, affecting the strength of the relativistic effects (such as enhancement of the polarization fraction and rotation of the polarization angle). Measuring the polarization of hard X-rays reflected from the disk allows the geometry to be determined. Two competing models describe the disk–corona geometry for the hard spectral state of BHBs, based on spectral and timing measurements 2, 3. The radiation is affected by special/general relativistic effects, and can serve as a probe for the properties of the black hole and surrounding environment, if the accretion geometry is properly identified. The resulting release of gravitational energy leads to the emission of X-rays 1. Matter is transferred from the companion to the black hole, forming an accretion disk, corona and jet structures. ![]() Black hole binary (BHB) systems comprise a stellar-mass black hole and a closely orbiting companion star. ![]()
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