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The Hard State of the Highly Absorbed High Inclination Black Hole Binary Candidate Swift J1658.2–4242 Observed by NuSTAR and Swift

Xu, Yanjun and Harrison, Fiona A. and Kennea, Jamie A. and Walton, Dominic J. and Tomsick, John A. and Miller, Jon M. and Barret, Didier and Fabian, Andrew C. and Forster, Karl and Fürst, Felix and Gandhi, Poshak and García, Javier A. (2018) The Hard State of the Highly Absorbed High Inclination Black Hole Binary Candidate Swift J1658.2–4242 Observed by NuSTAR and Swift. Astrophysical Journal, 865 (1). Art. No. 18. ISSN 1538-4357. doi:10.3847/1538-4357/aada03.

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We present a spectral and timing analysis of the newly reported Galactic X-ray transient Swift J1658.2–4242 observed by Nuclear Spectroscopic Telescope Array (NuSTAR) and Swift. The broadband X-ray continuum is typical of a black hole binary in the bright hard state, with a photon index of Γ = 1.63 ± 0.02 and a low coronal temperature of kT_e = 22 ± 1 keV, corresponding to a low spectral cutoff well constrained by NuSTAR. Spectral modeling of the relativistic disk reflection features, consisting of a broad Fe Kα line and the Compton reflection hump, reveals that the black hole is rapidly spinning with the spin parameter of a* > 0.96, and the inner accretion disk is viewed at a high inclination angle of I = 64^(2 o)_(-3) (statistical errors, 90% confidence). The high inclination is independently confirmed by dips in the light curves, which can be explained by absorbing material located near the disk plane temporarily obscuring the central region. In addition, we detect an absorption line in the NuSTAR spectra centered at 7.03^(+0.04)_(-0.03) keV. If associated with ionized Fe K absorption lines, this provides evidence for the presence of outflowing material in the low/hard state of a black hole binary candidate. A timing analysis shows the presence of a type-C quasi-periodic oscillation in the power spectrum, with the frequency increasing from ~0.14 to ~0.21 Hz during the single NuSTAR exposure. Our analysis reveals that Swift J1658.2–4242 displays characteristics typical for a black hole binary that is viewed at a high inclination angle, making it a good system for studying the accretion geometry in black hole binaries.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Xu, Yanjun0000-0003-2443-3698
Harrison, Fiona A.0000-0003-2992-8024
Kennea, Jamie A.0000-0002-6745-4790
Walton, Dominic J.0000-0001-5819-3552
Tomsick, John A.0000-0001-5506-9855
Barret, Didier0000-0002-0393-9190
Fabian, Andrew C.0000-0002-9378-4072
Forster, Karl0000-0001-5800-5531
Fürst, Felix0000-0003-0388-0560
Gandhi, Poshak0000-0003-3105-2615
García, Javier A.0000-0003-3828-2448
Additional Information:© 2018 The American Astronomical Society. Received 2018 May 18; revised 2018 July 30; accepted 2018 August 9; published 2018 September 18. We thank the referee for helpful comments that improved this work. D.J.W. acknowledges support from STFC Ernest Rutherford Fellowship. 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 the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS), jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA).
Group:NuSTAR, Space Radiation Laboratory, Astronomy Department
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:accretion, accretion disks – X-rays: binaries – X-rays: individual (Swift J1658.2-4242)
Issue or Number:1
Record Number:CaltechAUTHORS:20180918-091012752
Persistent URL:
Official Citation:Yanjun Xu et al 2018 ApJ 865 18
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89696
Deposited By: Tony Diaz
Deposited On:18 Sep 2018 16:47
Last Modified:16 Nov 2021 00:37

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