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
Abstract
We report results from joint Nuclear Spectroscopic Telescope Array, 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 quasi-periodic oscillation (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%. The 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.
Additional Information
© 2019 The American Astronomical Society. Received 2019 February 27; revised 2019 May 1; accepted 2019 May 23; published 2019 July 10. We thank the anonymous referee for the helpful comments that improved the paper. We thank Tom Russell and James Miller-Jones for providing information about ATCA radio observations. D.J.W. acknowledges support from the 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). This research has also made use of data obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States, and Swift, a NASA mission with participation of the Italian Space Agency (ASI) and the Particle Physics and Astronomy Research Council in the United Kingdom.Attached Files
Published - Xu_2019_ApJ_879_93.pdf
Submitted - 1905.10909.pdf
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Additional details
- Eprint ID
- 96517
- Resolver ID
- CaltechAUTHORS:20190619-085644567
- Science and Technology Facilities Council (STFC)
- NASA
- NNG08FD60C
- NASA/JPL/Caltech
- Created
-
2019-06-19Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- NuSTAR, Space Radiation Laboratory, Astronomy Department