THE REFLECTION COMPONENT FROM CYGNUS X-1 IN THE SOFT STATE MEASURED BY<i>NuSTAR</i>AND<i>SUZAKU</i>

Abstract

The black hole binary Cygnus X-1 was observed in late-2012 with the Nuclear\nSpectroscopic Telescope Array (NuSTAR) and Suzaku, providing spectral coverage\nover the ~1-300 keV range. The source was in the soft state with a\nmulti-temperature blackbody, power-law, and reflection components along with\nabsorption from highly ionized material in the system. The high throughput of\nNuSTAR allows for a very high quality measurement of the complex iron line\nregion as well as the rest of the reflection component. The iron line is\nclearly broadened and is well-described by a relativistic blurring model,\nproviding an opportunity to constrain the black hole spin. Although the spin\nconstraint depends somewhat on which continuum model is used, we obtain a*&gt;0.83\nfor all models that provide a good description of the spectrum. However, none\nof our spectral fits give a disk inclination that is consistent with the most\nrecently reported binary values for Cyg X-1. This may indicate that there is a\n&gt;13 degree misalignment between the orbital plane and the inner accretion disk\n(i.e., a warped accretion disk) or that there is missing physics in the\nspectral models.\n