http://arxiv.org/abs/2201.07360
We present a new analysis of NuSTAR and Suzaku observations of the black hole Cygnus X-1 in the intermediate state. The analysis makes use of kerrC, a new model for analyzing spectral and spectropolarimetric X-ray observations of black holes. kerrC builds on a large library of simulated black holes in X-ray binaries. The model accounts for the X-ray emission from a geometrically thin, optically thick accretion disk, the propagation of the X-rays through the curved black hole spacetime, the reflection off the accretion disk, and the Comptonization of photons in coronae of different 3-D shapes and physical properties before and after the reflection. We present the results from using kerrC for the analysis of archival NuSTAR and Suzaku observations taken on May 27-28, 2015. We find that kerrC can account for the overall shape of the energy spectrum, but not for the broad spectral 6-7 keV feature, thought to be relativistically broadened Fe k-alpha emission from the inner region of the accretion flow. A wedge-shaped corona fits the data slightly better than a cone-shaped corona. The analysis indicates a black hole spin parameter a between 0.861 and 0.921. The kerrC model provides new insights about the radial distribution of the energy flux of returning and coronal emission irradiating the accretion disk. We use kerrC to predict the polarization signatures that the recently launched Imaging X-ray Polarimetry Explorer will detect and find small, but measurable, polarization fractions on the order of 1%.
H. Krawczynski and B. Beheshtipour
Thu, 20 Jan 22
38/77
Comments: 21 pages, 9 figures, submitted to the Astrophysical Journal