Skip to main content

Research Repository

Advanced Search

The Lense-Thirring timing-accretion plane for ULXs

Middleton, M.; Fragile, P.C.; Ingram, A.; Roberts, T.P.

The Lense-Thirring timing-accretion plane for ULXs Thumbnail


M. Middleton

P.C. Fragile

A. Ingram


Identifying the compact object in ultraluminous X-ray sources (ULXs) has to-date required detection of pulsations or a cyclotron resonance scattering feature (CRSF), indicating a magnetised neutron star. However, pulsations are observed to be transient and it is plausible that accretion onto the neutron star may have suppressed the surface magnetic field such that pulsations and CRSFs will be entirely absent. We may therefore lack direct means to identify neutron star systems whilst we presently lack an effective means by which to identify black hole ULXs. Here we present a possible method for separating the ULX population by assuming the X-ray, mHz quasi-periodic oscillations (QPOs) and day timescale periods/QPOs are associated with Lense-Thirring precession of the inflow and outflowing wind respectively. The precession timescales combined with the temperature of the soft X-ray component produce planes where the accretor mass enters as a free parameter. Depending on the properties of the wind, use of these planes may be robust to a range in the angular momentum (spin) and, for high accretion rates, essentially independent of the neutron star’s surface dipole field strength. Our model also predicts the mHz QPO frequency and magnitude of the phase-lag imprinted due to propagation through the optically thick wind; in the case of NGC 5408 X-1 we subsequently infer a black hole mass and moderate-to-high spin. Finally, we note that observing secular QPO evolution over sufficient baselines may indicate a neutron star, as the precession responds to spin-up which is not readily observable for black hole primaries.


Middleton, M., Fragile, P., Ingram, A., & Roberts, T. (2019). The Lense-Thirring timing-accretion plane for ULXs. Monthly Notices of the Royal Astronomical Society, 489(1), 282-296.

Journal Article Type Article
Acceptance Date Jul 5, 2019
Online Publication Date Jul 25, 2019
Publication Date Oct 31, 2019
Deposit Date Jul 16, 2019
Publicly Available Date Aug 2, 2019
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 489
Issue 1
Pages 282-296
Related Public URLs


Accepted Journal Article (8.9 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

You might also like

Downloadable Citations