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Measuring A Truncated Disk in Aquila X-1

King, Ashley L. and Tomsick, John A. and Miller, Jon M. and Chenevez, Jérôme and Barret, Didier and Boggs, Steven E. and Chakrabarty, Deepto and Christensen, Finn E. and Craig, William W. and Fürst, Felix and Hailey, Charles J. and Harrison, Fiona A. and Parker, Michael L. and Stern, Daniel and Romano, Patrizia and Walton, Dominic J. and Zhang, William W. (2016) Measuring A Truncated Disk in Aquila X-1. Astrophysical Journal Letters, 819 (2). Art. No. L29. ISSN 2041-8205. doi:10.3847/2041-8205/819/2/L29.

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We present NuSTAR and Swift observations of the neutron star Aquila X-1 during the peak of its 2014 July outburst. The spectrum is soft with strong evidence for a broad Fe Kα line. Modeled with a relativistically broadened reflection model, we find that the inner disk is truncated with an inner radius of 15 ± 3R_G. The disk is likely truncated by either the boundary layer and/or a magnetic field. Associating the truncated inner disk with pressure from a magnetic field gives an upper limit of B<5 ± 2 x 10^8 G. Although the radius is truncated far from the stellar surface, material is still reaching the neutron star surface as evidenced by the X-ray burst present in the NuSTAR observation.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Tomsick, John A.0000-0001-5506-9855
Chenevez, Jérôme0000-0002-4397-8370
Barret, Didier0000-0002-0393-9190
Boggs, Steven E.0000-0001-9567-4224
Chakrabarty, Deepto0000-0001-8804-8946
Christensen, Finn E.0000-0001-5679-1946
Fürst, Felix0000-0003-0388-0560
Harrison, Fiona A.0000-0003-2992-8024
Parker, Michael L.0000-0002-8466-7317
Stern, Daniel0000-0003-2686-9241
Walton, Dominic J.0000-0001-5819-3552
Zhang, William W.0000-0002-1426-9698
Additional Information:© 2016 American Astronomical Society. Received 2015 October 19; accepted 2016 February 22; published 2016 March 7. The authors thank the referee for their invaluable comments. A.L.K. would like to thank the support for this work, which was provided by NASA through Einstein Postdoctoral Fellowship grant number PF4-150125 awarded by the Chandra X-ray Center, operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. P.R. acknowledges financial contribution from contract ASI-INAF I/004/11/0 and ASI-INAF I/037/12/0. J.C. is grateful for financial support from ESA/PRODEX No. 90057. This work 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. 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).
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
NASA Einstein FellowshipPF4-150125
Agenzia Spaziale Italiana (ASI)I/004/ 11/0
Agenzia Spaziale Italiana (ASI)I/037/12/0
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Subject Keywords:accretion, accretion disks; magnetic fields; stars: neutron; X-rays: binaries; X-rays: bursts
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2016-62
Issue or Number:2
Record Number:CaltechAUTHORS:20160318-071512595
Persistent URL:
Official Citation:Ashley L. King et al 2016 ApJ 819 L29
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:65468
Deposited By: Ruth Sustaita
Deposited On:18 Mar 2016 16:57
Last Modified:10 Nov 2021 23:46

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