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Relativistic Disk Reflection in the Neutron Star X-ray Binary XTE J1709-267 with NuSTAR

Ludlam, R. M. and Miller, J. M. and Cackett, E. C. and Degenaar, N. and Bostrom, A. C. (2017) Relativistic Disk Reflection in the Neutron Star X-ray Binary XTE J1709-267 with NuSTAR. Astrophysical Journal, 838 (2). Art. No. 79. ISSN 1538-4357. doi:10.3847/1538-4357/aa661a.

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We perform the first reflection study of the soft X-ray transient and Type 1 burst source XTE J1709-267 using NuSTAR observations during its 2016 June outburst. There was an increase in flux near the end of the observations, which corresponds to an increase from ~0.04 L_(Edd) to ~0.06 L_(Edd) assuming a distance of 8.5 kpc. We have separately examined spectra from the low- and high-flux intervals, which are soft and show evidence of a broad Fe K line. Fits to these intervals with relativistic disk reflection models have revealed an inner-disk radius of 13.8^(+3.0)_(-1.8) Rg (where R_g = GM/c^2) for the low-flux spectrum and 23.4^(+15.6)_(-5.4) Rg for the high-flux spectrum at the 90% confidence level. The disk is likely truncated by a boundary layer surrounding the neutron star (NS) or the magnetosphere. Based on the measured luminosity and the accretion efficiency for a disk around an NS, we estimate that the theoretically expected size for the boundary layer would be ~0.9-1.1 R_g from the NS's surface, which can be increased by spin or viscosity effects. Another plausible scenario is that the disk could be truncated by the magnetosphere. We place a conservative upper limit on the strength of the magnetic field at the poles (assuming a* = 0 and M_(NS) = 1.4M⊙) of B ⩽ 0.75 – 3.70 x 10^9 G, though X-ray pulsations have not been detected from this source.

Item Type:Article
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URLURL TypeDescription Paper
Ludlam, R. M.0000-0002-8961-939X
Cackett, E. C.0000-0002-8294-9281
Additional Information:© 2017 The American Astronomical Society. Received 2016 December 2; revised 2017 March 4; accepted 2017 March 8; published 2017 March 29. We thank the referee for their thoughtful comments that have led to the improvement of this work. R.M.L. would like to thank Fiona Harrison for the approval of the DDT that made this work possible. This research has made use of the NuSTAR Data Analysis Software, jointly developed by the ASI Science Data Center (Italy) and Caltech (USA). N.D. is supported by an NWO Vidi grant and a Marie Curie Intra-European Fellowship. E.M.C. gratefully acknowledges support from the National Science Foundation through CAREER award number AST-1351222.
Subject Keywords:accretion, accretion disks – stars: individual (XTE J1709-267) – stars: neutron – X-rays: binaries
Issue or Number:2
Record Number:CaltechAUTHORS:20170310-093522243
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Official Citation:R. M. Ludlam et al 2017 ApJ 838 79
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75019
Deposited By: Joy Painter
Deposited On:10 Mar 2017 19:25
Last Modified:15 Nov 2021 16:30

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