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We present a new analysis of NuSTAR and Suzaku observations of the black holeCygnus X-1 in the intermediate state. The analysis uses kerrC, a new model foranalyzing spectral and spectropolarimetric X-ray observations of black holes.kerrC builds on a large library of simulated black holes in X-ray binaries. Themodel accounts for the X-ray emission from a geometrically thin, opticallythick accretion disk, the propagation of the X-rays through the curved blackhole spacetime, the reflection off the accretion disk, and the Comptonizationof photons in coronae of different 3-D shapes and physical properties beforeand after the reflection. We present the results from using kerrC for theanalysis of archival NuSTAR and Suzaku observations taken on May 27-28, 2015.The best wedge-shaped corona gives a better fit than the cone-shaped corona.Although we included cone-shaped coronae in the funnel regions above and belowthe black hole to resemble to some degree the common assumption of a compactlamppost corona hovering above and/or below the black hole, the fit chooses avery large version of this corona that makes it possible to Comptonize asufficiently large fraction of the accretion disk photons to explain theobserved power law emission. The analysis indicates a dimensionless black holespin parameter a between 0.86 and 0.92. The kerrC model provides new insightsabout the radial distribution of the energy flux of returning and coronalemission irradiating the accretion disk. kerrC furthermore predicts smallpolarization fractions around 1% in the 2-8 keV energy range of the recentlylaunched Imaging X-ray Polarimetry Explorer.

New Constraints on the Spin of the Black Hole Cygnus X-1 and the Physical Properties of its Accretion Disk Corona