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

Middleton, M. J. and Fragile, P. C. and Bachetti, M. and Brightman, M. and Jiang, Y.-F. and Ho, W. C. G. and Roberts, T. P. and Ingram, A. R. and Dauser, T. and Pinto, C. and Walton, D. J. and Fuerst, F. and Fabian, A. C. and 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). pp. 154-166. ISSN 0035-8711.

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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-time-scale periods (60-80 d) 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 is 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Middleton, M. J.0000-0002-8183-2970
Bachetti, M.0000-0002-4576-9337
Brightman, M.0000-0002-8147-2602
Ho, W. C. G.0000-0002-6089-6836
Roberts, T. P.0000-0001-8252-6337
Ingram, A. R.0000-0002-5311-9078
Dauser, T.0000-0003-4583-9048
Pinto, C.0000-0003-2532-7379
Walton, D. J.0000-0001-5819-3552
Fuerst, F.0000-0003-0388-0560
Fabian, A. C.0000-0002-9378-4072
Additional Information:© 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 November 17. Received 2017 November 9; in original form 2017 August 11. The authors thank the anonymous referee. MJM appreciates support from an Ernest Rutherford STFC fellowship. WCGH acknowledges support from STFC in the UK. TPR acknowledges funding from STFC as part of the consolidated grants ST/L00075X/1 and ST/P000541/1. AI acknowledges support from NWO Veni grant 639.041.437. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-11259. CP and ACF acknowledge support from ERC Advanced Grant number 340442. This work is based on observations obtained with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)ST/L00075X/1
Science and Technology Facilities Council (STFC)ST/P000541/1
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)639.041.437
European Research Council (ERC)340442
Subject Keywords:accretion, accretion discs – black hole physics – stars: neutron – X-rays: binaries
Issue or Number:1
Record Number:CaltechAUTHORS:20180411-135404702
Persistent URL:
Official Citation:M J Middleton, P C Fragile, M Bachetti, M Brightman, Y-F Jiang, W C G Ho, T P Roberts, A R Ingram, T Dauser, C Pinto, D J Walton, F Fuerst, A C Fabian, N Gehrels; Lense-Thirring precession in ULXs as a possible means to constrain the neutron star equation of state, Monthly Notices of the Royal Astronomical Society, Volume 475, Issue 1, 21 March 2018, Pages 154–166,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85762
Deposited By: George Porter
Deposited On:11 Apr 2018 22:00
Last Modified:17 Dec 2019 21:59

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