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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

The hard state of the highly absorbed high inclination black hole binary candidate swift J1658.2-4242 observed by NuSTAR and swift
The hard state of the highly absorbed high inclination black hole binary candidate swift J1658.2-4242 observed by NuSTAR and swift

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 K 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° 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+0.0.4 -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.

accretion, accretion disks, X-rays: binaries, X-rays: individual (Swift J1658.2-4242)
0004-637X
1-9
Xu, Yanjun
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Harrison, Fiona A.
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Kennea, Jamie A.
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Walton, Dominic J.
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Tomsick, John A.
96b2e8cc-70c1-424a-8380-2551a5077ff5
Miller, Jon M.
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Barret, Didier
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Fabian, Andrew C.
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Forster, Karl
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Fürst, Felix
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Gandhi, Poshak
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Garcia, Javier A.
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Xu, Yanjun
4a78aef1-51eb-44bf-96c9-a1bcb956a100
Harrison, Fiona A.
d12bd352-3538-4dac-86fb-f13bc5837016
Kennea, Jamie A.
8a2485ff-bd59-4dd8-b6e3-d02e86bbc344
Walton, Dominic J.
3cf6ea78-7dd5-4765-8c09-ba2af76f11e7
Tomsick, John A.
96b2e8cc-70c1-424a-8380-2551a5077ff5
Miller, Jon M.
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Barret, Didier
66561ac0-81f1-4977-9ccc-b23c90d658e7
Fabian, Andrew C.
b9bef0bc-2ecd-49dc-ab2b-954cabea88ba
Forster, Karl
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Fürst, Felix
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Gandhi, Poshak
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Garcia, Javier A.
0783c08d-c7e1-48fd-a280-0e36c30b0208

Xu, Yanjun, Harrison, Fiona A., Kennea, Jamie A., Walton, Dominic J., Tomsick, John A., Miller, Jon M., Barret, Didier, Fabian, Andrew C., Forster, Karl, Fürst, Felix, Gandhi, Poshak and Garcia, 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), 1-9, [18]. (doi:10.3847/1538-4357/aada03).

Record type: Article

Abstract

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 K 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° 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+0.0.4 -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.

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1805.07705v2 - Accepted Manuscript
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Accepted/In Press date: 9 August 2018
e-pub ahead of print date: 18 September 2018
Published date: 20 September 2018
Keywords: accretion, accretion disks, X-rays: binaries, X-rays: individual (Swift J1658.2-4242)

Identifiers

Local EPrints ID: 425284
URI: http://eprints.soton.ac.uk/id/eprint/425284
ISSN: 0004-637X
PURE UUID: 116db005-c74b-476a-9a5a-324920643a87
ORCID for Poshak Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

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Date deposited: 12 Oct 2018 16:30
Last modified: 09 Oct 2020 16:37

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Contributors

Author: Yanjun Xu
Author: Fiona A. Harrison
Author: Jamie A. Kennea
Author: Dominic J. Walton
Author: John A. Tomsick
Author: Jon M. Miller
Author: Didier Barret
Author: Andrew C. Fabian
Author: Karl Forster
Author: Felix Fürst
Author: Poshak Gandhi ORCID iD
Author: Javier A. Garcia

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