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Title: Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13
Authors: Fuerst, F.
Walton, D. J.
Rana, V
+12 Co-Authors
Keywords: accretion
accretion disks
pulsars: individual: NGC 7793 P13
stars: neutron
X-rays: binaries
Issue Date: 10-Nov-2016
Publisher: IOP Sciences for American Astronomical Society
Citation: The Astrophysical Journal Letters, 2016, Vol.831, p6
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 ≈1040 {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 × 1012 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.
Description: Open Access
ISSN: 0004-637X
1538-4357 (online)
Alternative Location:
Copyright: 2016 The American Astronomical Society.
Appears in Collections:Research Papers (A&A)

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