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NuSTAR Observations of the Black Hole GS 1354–645: Evidence of Rapid Black Hole Spin

El-Batal, A. M. and Miller, J. M. and Reynolds, M. T. and Boggs, S. E. and Chistensen, F. E. and Craig, W. W. and Fuerst, F. and Hailey, C. J. and Harrison, F. A. and Stern, D. K. and Tomsick, J. and Walton, D. J. and Zhang, W. W. (2016) NuSTAR Observations of the Black Hole GS 1354–645: Evidence of Rapid Black Hole Spin. Astrophysical Journal Letters, 826 (1). Art. No. L12. ISSN 2041-8205. doi:10.3847/2041-8205/826/1/L12.

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We 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^2 ⩾ 0.98 (1σ statistical limits only). The fits also require a high inclination: Θ ≃ 75(2)°. 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Boggs, S. E.0000-0001-9567-4224
Fuerst, F.0000-0003-0388-0560
Harrison, F. A.0000-0003-2992-8024
Stern, D. K.0000-0003-2686-9241
Tomsick, J.0000-0001-5506-9855
Walton, D. J.0000-0001-5819-3552
Zhang, W. W.0000-0002-1426-9698
Additional Information:© 2016 The American Astronomical Society. Received 2016 May 18; revised 2016 June 30; accepted 2016 July 1; published 2016 July 19. We thank the anonymous referee for comments that improved this manuscript. This work was supported under NASA contract No. NNG08FD60C, and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by NASA.
Funding AgencyGrant Number
Subject Keywords:accretion, accretion disks – black hole physics – X-rays: binaries
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2016-40
Issue or Number:1
Record Number:CaltechAUTHORS:20160729-135241747
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69323
Deposited By: Tony Diaz
Deposited On:29 Jul 2016 21:06
Last Modified:11 Nov 2021 04:12

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