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Lense-Thirring precession in ULXs as a possible means to constrain the neutron star equation-of-state

Middleton, M.J.; Fragile, P.C.; Bachetti, M.; Brightman, M.; Jiang, Y-F.; Ho, W.G.C.; Roberts, T.P.; Ingram, A.R.; Dauser, T.; Pinto, C.; Walton, D.J.; Fuerst, F.; Fabian, A.C.; Gehrels, N.

Lense-Thirring precession in ULXs as a possible means to constrain the neutron star equation-of-state Thumbnail


Authors

M.J. Middleton

P.C. Fragile

M. Bachetti

M. Brightman

Y-F. Jiang

W.G.C. Ho

A.R. Ingram

T. Dauser

C. Pinto

D.J. Walton

F. Fuerst

A.C. Fabian

N. Gehrels



Abstract

The presence of neutron stars in at least three ultraluminous X-ray sources is now firmly established and offers an unambiguous view of super-critical accretion. All three systems show long-timescale periods (60-80 days) in the X-rays and/or optical, two of which are known to be super-orbital in nature. Should the flow be classically super critical, i.e. the Eddington limit ixd s reached locally in the disc (implying surface dipole fields that are sub-magnetar in strength), then the large scale-height flow can precess through the Lense-Thirring effect which could provide an explanation for the observed super-orbital periods. By connecting the details of the Lense-Thirring effect with the observed pulsar spin period, we are able to infer the moment-of-inertia and therefore equation-of-state of the neutron star without relying on the inclination of, or distance to the system. We apply our technique to the case of NGC 7793 P13 and demonstrate that stronger magnetic fields imply stiffer equations of state. We discuss the caveats and uncertainties, many of which can be addressed through forthcoming radiative magnetohydrodynamic (RMHD) simulations and their connection to observation.

Citation

Middleton, M., Fragile, P., Bachetti, M., Brightman, M., Jiang, Y., Ho, W., …Gehrels, N. (2018). Lense-Thirring precession in ULXs as a possible means to constrain the neutron star equation-of-state. Monthly Notices of the Royal Astronomical Society, 475(1), 154-166. https://doi.org/10.1093/mnras/stx2986

Journal Article Type Article
Acceptance Date Nov 17, 2017
Online Publication Date Nov 23, 2017
Publication Date Mar 1, 2018
Deposit Date Nov 22, 2017
Publicly Available Date Nov 28, 2017
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 475
Issue 1
Pages 154-166
DOI https://doi.org/10.1093/mnras/stx2986
Related Public URLs https://arxiv.org/abs/1711.07497

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Accepted Journal Article (316 Kb)
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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2017. The Authors.
Published by Oxford University Press on behalf of the Royal Astronomical Society.






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