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Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13

Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13
Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13
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 (Gt5σ) detection of coherent pulsations demonstrates that the compact object in P13 is a neutron star, and given the observed peak luminosity of ≈1040 $\mathrm{erg}\,{{\rm{s}}}^{-1}$ (assuming isotropy), it is well above the Eddington limit for a 1.4 ${M}_{\odot }$ 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.
2041-8205
Furst, F.
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Walton, D.J.
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Harrison, F.A.
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Stern, D.
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Barret, D.
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Brightman, M.
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Fabian, A.C.
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Grefenstette, B.
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Madsen, K.K.
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Middleton, M.J.
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Miller, J.M.
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Pottschmidt, K.
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Ptak, A.
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Rana, V.
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Webb, N.
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Furst, F.
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Walton, D.J.
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Harrison, F.A.
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Stern, D.
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Barret, D.
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Brightman, M.
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Fabian, A.C.
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Grefenstette, B.
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Madsen, K.K.
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Middleton, M.J.
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Miller, J.M.
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Pottschmidt, K.
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Ptak, A.
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Rana, V.
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Webb, N.
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Furst, F., Walton, D.J., Harrison, F.A., Stern, D., Barret, D., Brightman, M., Fabian, A.C., Grefenstette, B., Madsen, K.K., Middleton, M.J., Miller, J.M., Pottschmidt, K., Ptak, A., Rana, V. and Webb, N. (2016) Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13. The Astrophysical Journal Letters, 831 (2), [L14]. (doi:10.3847/2041-8205/831/2/L14).

Record type: Article

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 (Gt5σ) detection of coherent pulsations demonstrates that the compact object in P13 is a neutron star, and given the observed peak luminosity of ≈1040 $\mathrm{erg}\,{{\rm{s}}}^{-1}$ (assuming isotropy), it is well above the Eddington limit for a 1.4 ${M}_{\odot }$ 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.

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DISCOVERY OF COHERENT PULSATIONS FROM THE ULTRALUMINOUS X-RAY SOURCE NGC 7793 P13 - Accepted Manuscript
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Accepted/In Press date: 15 October 2016
e-pub ahead of print date: 3 November 2016
Published date: 3 November 2016
Additional Information: Arxiv record Author Middleton confirms AM
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 412026
URI: http://eprints.soton.ac.uk/id/eprint/412026
ISSN: 2041-8205
PURE UUID: ed4b833f-76b8-46d9-b253-82dc878d75bd

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Date deposited: 05 Jul 2017 16:31
Last modified: 16 Dec 2019 18:55

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Contributors

Author: F. Furst
Author: D.J. Walton
Author: F.A. Harrison
Author: D. Stern
Author: D. Barret
Author: M. Brightman
Author: A.C. Fabian
Author: B. Grefenstette
Author: K.K. Madsen
Author: M.J. Middleton
Author: J.M. Miller
Author: K. Pottschmidt
Author: A. Ptak
Author: V. Rana
Author: N. Webb

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