MEASURING THE SPIN OF GRS 1915+105 WITH RELATIVISTIC DISK REFLECTION

• Main Authors: Blum, J. L. (Author), Miller, J. M. (Author), Fabian, Andrew C. (Author), Miller, M. Coleman (Author), Homan, Jeroen (Contributor), van der Klis, M. (Author), Cackett, E. M. (Author), Reis, R. C. (Author)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor)
• Format: Article
• Language: English
• Published: Institute of Physics/American Astronomical Society, 2015-03-05T15:48:27Z.
• Subjects: Article
• Online Access: Get fulltext

 GRS 1915+105 harbors one of the most massive known stellar black holes in the Galaxy. In 2007 May, we observed GRS 1915+105 for ~117 ks in the low/hard state using Suzaku. We collected and analyzed the data with the Hard X-ray Detector/Positive Intrinsic Negative and X-ray Spectrometer cameras spanning the energy range from 2.3 to 55 keV. Fits to the spectra with simple models reveal strong disk reflection through an Fe K emission line and a Compton backscattering hump. We report constraints on the spin parameter of the black hole in GRS 1915 + 105 using relativistic disk reflection models. The model for the soft X-ray spectrum (i.e., < 10 keV) suggests a = 0.56+0.02−0.02 and excludes zero spin at the 4σ level of confidence. The model for the full broadband spectrum suggests that the spin may be higher, a = 0.98+0.01−0.01 (1σ confidence), and again excludes zero spin at the 2σ level of confidence. We discuss these results in the context of other spin constraints and inner disk studies in GRS 1915 + 105.