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NuSTAR Observations of the Black Hole GS 1354-645: Evidence of Rapid Black Hole SpinWe present the results of a NuSTAR study of the dynamically confirmed stellar-mass black hole GS 1354−645. The source was observed during its 2015 "hard" state outburst; we concentrate on spectra from two relatively bright phases. In the higher-flux observation, the broadband NuSTAR spectra reveal a clear, strong disk reflection spectrum, blurred by a degree that requires a black hole spin of a = cJ/ GM(sup 2) > or = 0.98 (1(sigma) statistical limits only). The fits also require a high inclination: theta approx. = 75(2)deg. Strong "dips" are sometimes observed in the X-ray light curves of sources viewed at such an angle; these are absent, perhaps indicating that dips correspond to flared disk structures that only manifest at higher accretion rates. In the lower flux observation, there is evidence of radial truncation of the thin accretion disk. We discuss these results in the context of spin in stellar-mass black holes, and inner accretion flow geometries at moderate accretion rates.
Document ID
20170003107
Document Type
Reprint (Version printed in journal)
Authors
El-Batal, A. M. (Michigan Univ. Ann Arbor, MI, United States)
Miller, J. M. (Michigan Univ. Ann Arbor, MI, United States)
Reynolds, M. T. (Michigan Univ. Ann Arbor, MI, United States)
Boggs, S. E. (California Univ. Berkeley, CA, United States)
Christensen, F. E. (Danish Academy of Technical Sciences Lyngby, Denmark)
Craig, W. W. (Lawrence Livermore National Lab. Livermore, CA, United States)
Fuerst, F. (California Inst. of Tech. Pasadena, CA, United States)
Hailey, C. J. (Columbia Univ. New York, NY, United States)
Harrison, F. A. (California Inst. of Tech. Pasadena, CA, United States)
Stern, D. K. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Tomsick, J. (California Univ. Berkeley, CA, United States)
Walton, D. J. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Zhang, W. W. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
April 6, 2017
Publication Date
July 19, 2016
Publication Information
Publication: The Astrophysical Journal Letters
Volume: 826
Issue: 1
ISSN: 2041-8205
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN41102
Funding Number(s)
CONTRACT_GRANT: NNG08FD60C
Distribution Limits
Public
Copyright
Other
Keywords
accretion disks
accretion