Tomsick, John A.3; Nowak, Michael A.17; Parker, Michael17; Miller, Jon M.18; Fabian, Andy C.19; Harrison, Fiona A.20; Bachetti, Matteo8; Barret, Didier8; Boggs, Steven E.9; Christensen, Finn Erland1; Craig, William W.10; Forster, Karl20; Fuerst, Felix20; Grefenstette, Brian W.20; Hailey, Charles J.21; King, Ashley L.18; Madsen, Kristin K.20; Natalucci, Lorenzo12; Pottschmidt, Katja22; Ross, Randy R.23; Stern, Daniel15; Walton, Dominic J.20; Wilms, Joern16; Zhang, William W.22
1 National Space Institute, Technical University of Denmark2 Astrophysics, National Space Institute, Technical University of Denmark3 unknown4 Massachusetts Institute of Technology5 University of Michigan6 University of Cambridge7 California Institute of Technology8 Centre National de la Recherche Scientifique9 SSL/UCB10 SSL/UCB and LLNL11 Columbia University12 National Institute for Astrophysics13 NASA Goddard Space Flight Center14 College of the Holy Cross15 NASA Jet Propulsion Laboratory16 Dr. Karl-Remeis-Sternwarte and Erlangen Center for Astroparticle Physics17 Massachusetts Institute of Technology18 University of Michigan19 University of Cambridge20 California Institute of Technology21 Columbia University22 NASA Goddard Space Flight Center23 College of the Holy Cross
The black hole binary Cygnus X-1 was observed in late-2012 with the Nuclear Spectroscopic Telescope Array (NuSTAR) and Suzaku, providing spectral coverage over the ~1-300 keV range. The source was in the soft state with a multi-temperature blackbody, power-law, and reflection components along with absorption from highly ionized material in the system. The high throughput of NuSTAR allows for a very high quality measurement of the complex iron line region as well as the rest of the reflection component. The iron line is clearly broadened and is well-described by a relativistic blurring model, providing an opportunity to constrain the black hole spin. Although the spin constraint depends somewhat on which continuum model is used, we obtain a*>0.83 for all models that provide a good description of the spectrum. However, none of our spectral fits give a disk inclination that is consistent with the most recently reported binary values for Cyg X-1. This may indicate that there is a >13 degree misalignment between the orbital plane and the inner accretion disk (i.e., a warped accretion disk) or that there is missing physics in the spectral models.