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Spectral Changes in the Hyperluminous Pulsar in NGC 5907 as a Function of Super-Orbital Phase

Fürst, F. and Walton, D. J. and Stern, D. and Bachetti, M. and Barret, D. and Brightman, M. and Harrison, F. A. and Rana, V. (2017) Spectral Changes in the Hyperluminous Pulsar in NGC 5907 as a Function of Super-Orbital Phase. Astrophysical Journal, 834 (1). Art. No. 77. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20170105-135606067

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Abstract

We present broadband, multi-epoch X-ray spectroscopy of the pulsating ultra-luminous X-ray source (ULX) in NGC 5907. Simultaneous XMM-Newton and NuSTAR data from 2014 are best described by a multicolor blackbody model with a temperature gradient as a function of accretion disk radius significantly flatter than expected for a standard thin accretion disk (T(r) α r^(-p), with p = 0.608__(-0.012)^(+0.014)). Additionally, we detect a hard power-law tail at energies above 10 keV, which we interpret as being due to Comptonization. We compare this observation to archival XMM-Newton, Chandra, and NuSTAR data from 2003, 2012, and 2013, and investigate possible spectral changes as a function of phase over the 78-day super-orbital period of this source. We find that observations taken around phases 0.3–0.4 show very similar temperature profiles, even though the observed flux varies significantly, while one observation taken around phase 0 has a significantly steeper profile. We discuss these findings in light of the recent discovery that the compact object is a neutron star and show that precession of the accretion disk or the neutron star can self-consistently explain most observed phenomena.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3847/1538-4357/834/1/77DOIArticle
http://iopscience.iop.org/article/10.3847/1538-4357/834/1/77/metaPublisherArticle
https://arxiv.org/abs/1610.00258arXivDiscussion Paper
ORCID:
AuthorORCID
Walton, D. J.0000-0001-5819-3552
Stern, D.0000-0003-2686-9241
Bachetti, M.0000-0002-4576-9337
Harrison, F. A.0000-0003-2992-8024
Rana, V.0000-0003-1703-8796
Additional Information:© 2017. The American Astronomical Society. Received 2016 September 30; revised 2016 November 11; accepted 2016 November 11; published 2017 January 4. We thank the referee for useful comments that helped to improve the manuscript. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. 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). This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. This research has made use of a collection of ISIS functions (ISISscripts) provided by ECAP/Remeis observatory and MIT (http://www.sternwarte.uni-erlangen.de/isis/). We would like to thank John E. Davis for the slxfig module, which was used to produce all figures in this work.The Swift/BAT transient monitor results were provided by the Swift/BAT team. Facilities: NuSTAR, XMM, Chandra, Swift.
Group:NuSTAR
Funders:
Funding AgencyGrant Number
ESA Member StatesUNSPECIFIED
NASANNG08FD60C
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:accretion, accretion disks; pulsars: individual (NGC 5907 ULX1) ; X-rays: binaries
Record Number:CaltechAUTHORS:20170105-135606067
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170105-135606067
Official Citation:F. Fürst et al 2017 ApJ 834 77
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73278
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:06 Jan 2017 16:31
Last Modified:29 Nov 2017 05:15

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