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Studying the Reflection Spectra of the New Black Hole X-Ray Binary Candidate MAXI J1631−479 Observed by NuSTAR: A Variable Broad Iron Line Profile

Xu, Yanjun and Harrison, Fiona A. and Tomsick, John A. and Walton, Dominic J. and Barret, Didier and García, Javier A. and Hare, Jeremy and Parker, Michael L. (2020) Studying the Reflection Spectra of the New Black Hole X-Ray Binary Candidate MAXI J1631−479 Observed by NuSTAR: A Variable Broad Iron Line Profile. Astrophysical Journal, 893 (1). Art. No. 30. ISSN 1538-4357. doi:10.3847/1538-4357/ab7dc0.

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We present results from the Nuclear Spectroscopic Telescope Array observations of the new black hole X-ray binary candidate MAXI J1631–479 at two epochs during its 2018–2019 outburst, which caught the source in a disk dominant state and a power-law dominant state. Strong relativistic disk reflection features are clearly detected, displaying significant variations in the shape and strength of the broad iron emission line between the two states. Spectral modeling of the reflection spectra reveals that the inner radius of the optically thick accretion disk evolves from <1.9 r_g to 12 ± 1 r_g (statistical errors at 90% confidence level) from the disk dominant to the power-law dominant state. Assuming in the former case that the inner disk radius is consistent with being at the innermost stable circular orbit, we estimate a black hole spin of a* > 0.94. Given that the bolometric luminosity is similar in the two states, our results indicate that the disk truncation observed in MAXI J1631–479 in the power-law dominant state is unlikely to be driven by a global variation in the accretion rate. We propose that it may instead arise from local instabilities in the inner edge of the accretion disk at high accretion rates. In addition, we find an absorption feature in the spectra centered at 7.33 ± 0.03 keV during the disk dominant state, which is evidence for the rare case that an extremely fast disk wind (v_(out) = 0.067^(+0.001)_(−0.004) c) is observed in a low-inclination black hole binary, with the viewing angle of 29° ± 1° as determined by the reflection modeling.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Xu, Yanjun0000-0003-2443-3698
Harrison, Fiona A.0000-0003-2992-8024
Tomsick, John A.0000-0001-5506-9855
Walton, Dominic J.0000-0001-5819-3552
Barret, Didier0000-0002-0393-9190
García, Javier A.0000-0003-3828-2448
Hare, Jeremy0000-0002-8548-482X
Parker, Michael L.0000-0002-8466-7317
Additional Information:© 2020 The American Astronomical Society. Received 2019 August 26; revised 2020 March 5; accepted 2020 March 6; published 2020 April 13. We thank the referee for the constructive comments that improved this paper. D.J.W. acknowledges support from an STFC Ernest Rutherford fellowship. J.A.G. acknowledges support from NASA grant NNX17AJ65G and from the Alexander von Humboldt Foundation. J.H. acknowledges support from an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by the USRA through a contract with NASA. M.L.P. is supported by the European Space Agency (ESA) Research 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 MAXI data provided by RIKEN, JAXA, and the MAXI team.
Group:Astronomy Department, Space Radiation Laboratory, NuSTAR
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
European Space Agency (ESA)UNSPECIFIED
Subject Keywords:Accretion ; black hole physics; X-ray binary stars ; X-ray transient sources
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Accretion (14); Black hole physics (159); X-ray binary stars (1811); X-ray transient sources (1852)
Record Number:CaltechAUTHORS:20200413-123514628
Persistent URL:
Official Citation:Yanjun Xu et al 2020 ApJ 893 30
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102508
Deposited By: Tony Diaz
Deposited On:13 Apr 2020 21:58
Last Modified:16 Nov 2021 18:12

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