CONFIRMATION VIA THE CONTINUUM-FITTING METHOD THAT THE SPIN OF THE BLACK HOLE IN CYGNUS X-1 IS EXTREME
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Gou-2014-Confirmation via the.pdf
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Author(s)
Gou, Lijun
McClintock, Jeffrey E.
Steiner, James F.
Reid, Mark J.
Orosz, Jerome A.
Narayan, Ramesh
Hanke, Manfred
Garcia, Javier A.
Remillard, Ronald A
Date Issued
July 2014
Journal
Astrophysical Journal
Publisher
Institute of Physics/American Astronomical Society
Citation
Gou, Lijun, Jeffrey E. McClintock, Ronald A. Remillard, James F. Steiner, Mark J. Reid, Jerome A. Orosz, Ramesh Narayan, Manfred Hanke, and Javier Garcia. “CONFIRMATION VIA THE CONTINUUM-FITTING METHOD THAT THE SPIN OF THE BLACK HOLE IN CYGNUS X-1 IS EXTREME.” The Astrophysical Journal 790, no. 1 (June 30, 2014): 29. © 2014 American Astronomical Society.
Version
Final published version
Abstract
In Gou et al., we reported that the black hole primary in the X-ray binary Cygnus X-1 is a near-extreme Kerr black hole with a spin parameter a * > 0.95 (3σ). We confirm this result while setting a new and more stringent limit: a * > 0.983 at the 3σ (99.7%) confidence level. The earlier work, which was based on an analysis of all three useful spectra that were then available, was possibly biased by the presence in these spectra of a relatively strong Compton power-law component: the fraction of the thermal seed photons scattered into the power law was f s = 23%-31%, while the upper limit for reliable application of the continuum-fitting method is f s lsim 25%. We have subsequently obtained six additional spectra of Cygnus X-1 suitable for the measurement of spin. Five of these spectra are of high quality with f s in the range 10%-19%, a regime where the continuum-fitting method has been shown to deliver reliable results. Individually, the six spectra give lower limits on the spin parameter that range from a * > 0.95 to a * > 0.98, allowing us to conservatively conclude that the spin of the black hole is a * > 0.983 (3σ).
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1088/0004-637X/790/1/29
