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A NuSTAR Observation of the Reflection Spectrum of the Low-mass X-Ray Binary 4U 1728-34

Sleator, Clio C. and Tomsick, John A. and King, Ashley L. and Miller, Jon M. and Boggs, Steven E. and Bachetti, Matteo and Barret, Didier and Chenevez, Jérôme and Christensen, Finn E. and Craig, William W. and Hailey, Charles J. and Harrison, Fiona A. and Rahoui, Farid and Stern, Daniel K. and Walton, Dominic J. and Zhang, William W. (2016) A NuSTAR Observation of the Reflection Spectrum of the Low-mass X-Ray Binary 4U 1728-34. Astrophysical Journal, 827 (2). Art. No. 134. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20160817-123809585

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Abstract

We report on a simultaneous NuSTAR and Swift observation of the neutron star low-mass X-ray binary 4U 1728-34. We identified and removed four Type I X-ray bursts during the observation in order to study the persistent emission. The continuum spectrum is hard and described well by a blackbody with kT = 1.5 keV and a cutoff power law with Γ = 1.5, and a cutoff temperature of 25 keV. Residuals between 6 and 8 keV provide strong evidence of a broad Fe Kα line. By modeling the spectrum with a relativistically blurred reflection model, we find an upper limit for the inner disk radius of R_(in) ⩽ 2R_(ISCO). Consequently, we find that R_(NS) ⩽ 23 km, assuming M = 1.4 M_⊙ and a = 0.15. We also find an upper limit on the magnetic field of B ⩽ 2 × 10^8 G.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3847/0004-637X/827/2/134DOIArticle
http://iopscience.iop.org/article/10.3847/0004-637X/827/2/134/metaPublisherArticle
https://arxiv.org/abs/1605.02137arXivDiscussion Paper
ORCID:
AuthorORCID
Boggs, Steven E.0000-0001-9567-4224
Bachetti, Matteo0000-0002-4576-9337
Harrison, Fiona A.0000-0003-2992-8024
Rahoui, Farid0000-0001-7655-4120
Stern, Daniel K.0000-0003-2686-9241
Walton, Dominic J.0000-0001-5819-3552
Additional Information:© 2016 The American Astronomical Society. Received 2016 February 9; revised 2016 June 17; accepted 2016 June 25; published 2016 August 18. We thank Michael Parker and Andy Fabian for the particular version of the reflionx model used in this analysis. We thank Kristin Madsen for her help identifying the calibration issue in the NuSTAR data between 3–4.5 keV. J.C. thanks ESA/PRODEX for financial support. This work is based on data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by NASA.
Group:NuSTAR
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
ESA-PRODEX (Belgium)UNSPECIFIED
Subject Keywords:accretion, accretion disks – stars: neutron – X-rays: binaries
Record Number:CaltechAUTHORS:20160817-123809585
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160817-123809585
Official Citation:Clio C. Sleator et al 2016 ApJ 827 134
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69708
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Aug 2016 21:28
Last Modified:30 Nov 2017 16:55

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