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The Evolution of GX 339-4 in the Low-hard State as Seen by NuSTAR and Swift

Wang-Ji, Jingyi and García, Javier A. and Steiner, James F. and Tomsick, John A. and Harrison, Fiona A. and Bambi, Cosimo and Petrucci, Pierre-Olivier and Ferreira, Jonathan and Chakravorty, Susmita and Clavel, Maïca (2018) The Evolution of GX 339-4 in the Low-hard State as Seen by NuSTAR and Swift. Astrophysical Journal, 855 (1). Art. No. 61. ISSN 1538-4357. doi:10.3847/1538-4357/aaa974.

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We analyze 11 Nuclear Spectroscopic Telescope Array and Swift observations of the black hole X-ray binary GX 339–4 in the hard state, 6 of which were taken during the end of the 2015 outburst and 5 during a failed outburst in 2013. These observations cover luminosities from 0.5% to 5% of the Eddington luminosity. Implementing the most recent version of the reflection model relxillCp, we perform simultaneous spectral fits on both data sets to track the evolution of the properties in the accretion disk, including the inner edge radius, the ionization, and the temperature of the thermal emission. We also constrain the photon index and electron temperature of the primary source (the "corona"). We observe a maximum truncation radius of 37 R_g in the preferred fit for the 2013 data set, and a marginal correlation between the level of truncation and luminosity. We also explore a self-consistent model under the framework of coronal Comptonization, and find consistent results regarding the disk truncation in the 2015 data, providing a more physical preferred fit for the 2013 observations.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
García, Javier A.0000-0003-3828-2448
Steiner, James F.0000-0002-5872-6061
Tomsick, John A.0000-0001-5506-9855
Harrison, Fiona A.0000-0003-2992-8024
Bambi, Cosimo0000-0002-3180-9502
Clavel, Maïca0000-0003-0724-2742
Additional Information:© 2018 The American Astronomical Society. Received 2017 November 15; revised 2018 January 9; accepted 2018 January 19; published 2018 March 8. Part of this work was carried out by JW during attendance to the Summer Undergraduate Research Fellowship (SURF) at California Institute of Technology in 2017. Warm hospitality and tutelage are kindly acknowledged, in particular from the members of the NuSTAR Science Operations Team (K. Foster, B. Grenfestette, K. Madsen, M. Heida, M. Brightman, and D. Stern). We would like to thank the referee for useful comments toward the improvement of this paper. We also thank B. de Marco and G. Ponti for useful discussions. J.A.G. acknowledges support from NASA grants NNX17AJ65G and 80NSSC177K0515, and from the Alexander von Humboldt Foundation. J.F.S. has been supported by NASA Hubble Fellowship grant HST-HF-51315.01. S.C. is supported by the SERB National Postdoctoral Fellowship (No. PDF/2017/000841). We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations.
Group:NuSTAR, Space Radiation Laboratory, Astronomy Department
Funding AgencyGrant Number
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
NASA Hubble FellowshipHST-HF-51315.01
Science and Engineering Research Board (SERB)PDF/2017/000841
Subject Keywords:accretion, accretion disks – black hole physics – line: formation – X-rays: individual (GX 339–4)
Issue or Number:1
Record Number:CaltechAUTHORS:20180308-105914434
Persistent URL:
Official Citation:Jingyi Wang-Ji et al 2018 ApJ 855 61
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85203
Deposited By: Tony Diaz
Deposited On:08 Mar 2018 21:37
Last Modified:15 Nov 2021 20:26

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