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NuSTAR Detection of hard x-ray phase lags from the accreting pulsar GS 0834-430

Miyasaka, H. and Bachetti, Matteo and Harrison, F. A. and Fürst, Felix and Barret, D. and Bellm, E. C. and Boggs, S. E. and Chakrabarty, D. and Chenevez, Jerome and Christensen, F. E. (2013) NuSTAR Detection of hard x-ray phase lags from the accreting pulsar GS 0834-430. Astrophysical Journal, 775 (1). Art. No. 65. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20150401-090934706

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Abstract

The Nuclear Spectroscopic Telescope Array hard X-ray telescope observed the transient Be/X-ray binary GS 0834-430 during its 2012 outburst-the first active state of this system observed in the past 19 yr. We performed timing and spectral analysis and measured the X-ray spectrum between 3-79 keV with high statistical significance. We find the phase-averaged spectrum to be consistent with that observed in many other magnetized, accreting pulsars. We fail to detect cyclotron resonance scattering features that would allow us to constrain the pulsar's magnetic field in either phase-averaged or phase-resolved spectra. Timing analysis shows a clearly detected pulse period of similar to 12.29 s in all energy bands. The pulse profiles show a strong, energy-dependent hard phase lag of up to 0.3 cycles in phase, or about 4 s. Such dramatic energy-dependent lags in the pulse profile have never before been reported in high-mass X-ray binary pulsars. Previously reported lags have been significantly smaller in phase and restricted to low energies (E < 10 keV). We investigate the possible mechanisms that might produce this energy-dependent pulse phase shift. We find the most likely explanation for this effect is a complex beam geometry.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/775/1/65DOIArticle
http://iopscience.iop.org/0004-637X/775/1/65/PublisherArticle
ORCID:
AuthorORCID
Bachetti, Matteo0000-0002-4576-9337
Harrison, F. A.0000-0003-2992-8024
Bellm, E. C.0000-0001-8018-5348
Boggs, S. E.0000-0001-9567-4224
Additional Information:© 2013 American Astronomical Society. Received 2013 June 3, accepted for publication 2013 July 25 Published 2013 September 5. 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. 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). Matteo Bachetti wishes to acknowledge the support from the Centre National d’Etudes Spatiales (CNES). Lorenzo Natalucci acknowledges financial support through contract ASI/INAF I/037/12/0.
Group:NuSTAR, Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NSFNNG08FD60C
NASA/JPL/CaltechUNSPECIFIED
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Agenxia Spaziale Italiana (ASI)I/037/12/0
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Record Number:CaltechAUTHORS:20150401-090934706
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150401-090934706
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56270
Collection:CaltechAUTHORS
Deposited By: Joy Painter
Deposited On:01 Apr 2015 17:05
Last Modified:28 Oct 2017 03:08

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