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Evidence for Disk Truncation at Low Accretion States of the Black Hole Binary MAXI J1820+070 Observed by NuSTAR and XMM-Newton

Xu, Yanjun and Harrison, Fiona A. and Tomsick, John A. and Hare, Jeremy and Fabian, Andrew C. and Walton, Dominic J. (2020) Evidence for Disk Truncation at Low Accretion States of the Black Hole Binary MAXI J1820+070 Observed by NuSTAR and XMM-Newton. Astrophysical Journal, 893 (1). Art. No. 42. ISSN 1538-4357. https://resolver.caltech.edu/CaltechAUTHORS:20200413-152859389

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Abstract

We present results from NuSTAR and XMM-Newton observations of the new black hole X-ray binary MAXI J1820+070 at low accretion rates (below 1% of the Eddington luminosity). We detect a narrow Fe Kα emission line, in contrast to the broad and asymmetric Fe Kα line profiles commonly present in black hole binaries at high accretion rates. The narrow line, with weak relativistic broadening, indicates that the Fe Kα line is produced at a large disk radius. Fitting with disk reflection models assuming standard disk emissivity finds a large disk truncation radius (a few tens to a few hundreds of gravitational radii, depending on the disk inclination). In addition, we detect a quasi-periodic oscillation (QPO) varying in frequency between 11.6 ± 0.2 mHz and 2.8 ± 0.1 mHz. The very low QPO frequencies suggest a large size for the optically thin Comptonization region according to the Lense–Thirring precession model, supporting that the accretion disk recedes from the innermost stable circular orbit and is replaced by advection-dominated accretion flow at low accretion rates. We also discuss the possibility of an alternative accretion geometry that the narrow Fe Kα line is produced by a lamppost corona with a large height illuminating the disk.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/ab7cdbDOIArticle
https://arxiv.org/abs/2003.01778arXivDiscussion Paper
ORCID:
AuthorORCID
Xu, Yanjun0000-0003-2443-3698
Harrison, Fiona A.0000-0003-2992-8024
Tomsick, John A.0000-0001-5506-9855
Hare, Jeremy0000-0002-8548-482X
Fabian, Andrew C.0000-0002-9378-4072
Walton, Dominic J.0000-0001-5819-3552
Additional Information:© 2020 The American Astronomical Society. Received 2020 January 26; revised 2020 March 2; accepted 2020 March 3; published 2020 April 14. We thank the referee for helpful comments that improved the paper. We thank Norbert Schartel for approving the XMM-Newton DDT observation and the XMM-Newton SOC for prompt scheduling of the observation. 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. D.J.W. acknowledge support from an 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.
Group:Astronomy Department, NuSTAR, Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASA Postdoctoral ProgramUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
NASANNG08FD60C
NASA/JPL/CaltechUNSPECIFIED
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 transient sources (1852); X-ray binary stars (1811)
Record Number:CaltechAUTHORS:20200413-152859389
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200413-152859389
Official Citation:Yanjun Xu et al 2020 ApJ 893 42
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102511
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 Apr 2020 22:39
Last Modified:14 Apr 2020 17:02

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