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Discovery of Coherent Pulsations from the Ultraluminous X-Ray Source NGC 7793 P13

Fürst, F. and Walton, D. J. and Harrison, F. A. and Stern, D. and Barret, D. and Brightman, M. and Fabian, A. C. and Grefenstette, B. and Madsen, K. K. and Middleton, M. J. and Miller, J. M. and Pottschmidt, K. and Ptak, A. and Rana, V. and Webb, N. (2016) Discovery of Coherent Pulsations from the Ultraluminous X-Ray Source NGC 7793 P13. Astrophysical Journal Letters, 831 (2). Art. No. L14. ISSN 2041-8205. http://resolver.caltech.edu/CaltechAUTHORS:20161104-130329124

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Abstract

We report the detection of coherent pulsations from the ultraluminous X-ray source (ULX) NGC 7793 P13. The ≈0.42 s nearly sinusoidal pulsations were initially discovered in broadband X-ray observations using XMM-Newton and NuSTAR taken in 2016. We subsequently also found pulsations in archival XMM-Newton data taken in 2013 and 2014. The significant (≫5σ) detection of coherent pulsations demonstrates that the compact object in P13 is a neutron star, and given the observed peak luminosity of ≈10^(40) erg s^(-1) (assuming isotropy), it is well above the Eddington limit for a 1.4 M⊙ accretor. This makes P13 the second ULX known to be powered by an accreting neutron star. The pulse period varies between epochs, with a slow but persistent spin-up over the 2013–2016 period. This spin-up indicates a magnetic field of B ≈ 1.5 × 10^(12) G, typical of many Galactic accreting pulsars. The most likely explanation for the extreme luminosity is a high degree of beaming; however, this is difficult to reconcile with the sinusoidal pulse profile.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3847/2041-8205/831/2/L14DOIArticle
http://iopscience.iop.org/article/10.3847/2041-8205/831/2/L14/metaPublisherArticle
https://arxiv.org/abs/1609.07129arXivDiscussion Paper
ORCID:
AuthorORCID
Walton, D. J.0000-0001-5819-3552
Harrison, F. A.0000-0003-2992-8024
Stern, D.0000-0003-2686-9241
Madsen, K. K.0000-0003-1252-4891
Ptak, A.0000-0001-5655-1440
Rana, V.0000-0003-1703-8796
Additional Information:© 2016 American Astronomical Society. Received 2016 September 22; revised 2016 October 10; accepted 2016 October 15; published 2016 November 3. We would like the thank the referee for the helpful comments. M.J.M. acknowledges support from an STFC Ernest Rutherford fellowship, A.C.F. acknowledges support from ERC Advanced Grant 340442, and D.B. acknowledges financial support from the French Space Agency (CNES). This research has made use of data obtained with NuSTAR, a project led by Caltech, funded by NASA and managed by NASA/JPL, and has utilized the nustardas software package, jointly developed by the ASDC (Italy) and Caltech (USA). This research has also made use of data obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester, and also made use of the XRT Data Analysis Software (XRTDAS) developed under the responsibility of the ASI Science Data Center (ASDC), Italy. 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/). Facilities: NuSTAR, XMM, Swift.
Group:NuSTAR, Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
European Research Council (ERC)340442
Centre National d'Études Spatiales (CNES)UNSPECIFIED
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:accretion, accretion disks – pulsars: individual (NGC 7793 P13) – stars: neutron – X-rays: binaries
Record Number:CaltechAUTHORS:20161104-130329124
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20161104-130329124
Official Citation:F. Fürst et al 2016 ApJL 831 L14
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71748
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:04 Nov 2016 20:12
Last Modified:30 Nov 2017 16:51

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