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Broadband X-ray spectral and timing analyses of the black hole binary candidate swift J1658.2-4242: rapid flux variation and the turn-on of a transient QPO

Broadband X-ray spectral and timing analyses of the black hole binary candidate swift J1658.2-4242: rapid flux variation and the turn-on of a transient QPO
Broadband X-ray spectral and timing analyses of the black hole binary candidate swift J1658.2-4242: rapid flux variation and the turn-on of a transient QPO
We report results from joint NuSTAR, Swift and XMM-Newton observations of the newly discovered black hole X-ray binary candidate Swift J1658.2–4242 in the intermediate state. We observe a peculiar event in this source, with its X-ray flux rapidly decreasing by ∼45% in ∼40 s, accompanied by only subtle changes in the shape of the broadband X-ray spectrum. In addition, we find a sudden turn-on of a transient QPO with a frequency of 6 − 7 Hz around the time of the flux change, and the total fractional rms amplitude of the power spectrum increases from ∼2% to ∼10%. X-ray spectral and timing analyses indicate that the flux decrease is driven by intrinsic changes in the accretion flow around the black hole, rather than intervening material along the line of sight. In addition, we do not significantly detect any relativistic disk reflection component, indicating it is much weaker than previously observed while the source was in the bright hard state. We propose accretion disk instabilities triggered at a large disk radius as the origin of the fast transition in spectral and timing properties, and discuss possible causes of the unusual properties observed in Swift J1658.2–4242. The prompt flux variation detected along with the emergence of a QPO makes the event an interesting case for investigating QPO mechanisms in black hole X-ray binaries.
0004-637X
1-12
Xu, Yanjun
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Harrison, Fiona A.
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Tomsick, John A.
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Barret, Didier
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Gandhi, Poshak
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Garcia, Javier
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Miller, Jon M.
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Uttley, Philip
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Walton, Dominic J.
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Xu, Yanjun
4a78aef1-51eb-44bf-96c9-a1bcb956a100
Harrison, Fiona A.
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Tomsick, John A.
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Barret, Didier
66561ac0-81f1-4977-9ccc-b23c90d658e7
Gandhi, Poshak
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Garcia, Javier
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Miller, Jon M.
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Uttley, Philip
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Walton, Dominic J.
3cf6ea78-7dd5-4765-8c09-ba2af76f11e7

Xu, Yanjun, Harrison, Fiona A., Tomsick, John A., Barret, Didier, Gandhi, Poshak, Garcia, Javier, Miller, Jon M., Uttley, Philip and Walton, Dominic J. (2019) Broadband X-ray spectral and timing analyses of the black hole binary candidate swift J1658.2-4242: rapid flux variation and the turn-on of a transient QPO. The Astrophysical Journal, 879 (2), 1-12, [93]. (doi:10.3847/1538-4357/ab24bf).

Record type: Article

Abstract

We report results from joint NuSTAR, Swift and XMM-Newton observations of the newly discovered black hole X-ray binary candidate Swift J1658.2–4242 in the intermediate state. We observe a peculiar event in this source, with its X-ray flux rapidly decreasing by ∼45% in ∼40 s, accompanied by only subtle changes in the shape of the broadband X-ray spectrum. In addition, we find a sudden turn-on of a transient QPO with a frequency of 6 − 7 Hz around the time of the flux change, and the total fractional rms amplitude of the power spectrum increases from ∼2% to ∼10%. X-ray spectral and timing analyses indicate that the flux decrease is driven by intrinsic changes in the accretion flow around the black hole, rather than intervening material along the line of sight. In addition, we do not significantly detect any relativistic disk reflection component, indicating it is much weaker than previously observed while the source was in the bright hard state. We propose accretion disk instabilities triggered at a large disk radius as the origin of the fast transition in spectral and timing properties, and discuss possible causes of the unusual properties observed in Swift J1658.2–4242. The prompt flux variation detected along with the emergence of a QPO makes the event an interesting case for investigating QPO mechanisms in black hole X-ray binaries.

Text
Broadband X-Ray Spectral and Timing Analyses of the Black Hole Binary Candidate Swift J1658.2-4242 Rapid Flux Variation and the Turn-on of a Transient QPO - Accepted Manuscript
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Accepted/In Press date: 23 May 2019
e-pub ahead of print date: 10 July 2019
Published date: July 2019

Identifiers

Local EPrints ID: 433114
URI: http://eprints.soton.ac.uk/id/eprint/433114
ISSN: 0004-637X
PURE UUID: 3b321881-b34e-4343-8ea1-42b3aa55af26
ORCID for Poshak Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

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Date deposited: 08 Aug 2019 16:30
Last modified: 09 Oct 2020 16:37

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Contributors

Author: Yanjun Xu
Author: Fiona A. Harrison
Author: John A. Tomsick
Author: Didier Barret
Author: Poshak Gandhi ORCID iD
Author: Javier Garcia
Author: Jon M. Miller
Author: Philip Uttley
Author: Dominic J. Walton

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