Issue |
A&A
Volume 643, November 2020
|
|
---|---|---|
Article Number | A171 | |
Number of page(s) | 14 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/202038857 | |
Published online | 20 November 2020 |
Models of ultraluminous X-ray transient sources
1
Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS UMR 7550, 67000 Strasbourg, France
e-mail: jean-marie.hameury@astro.unistra.fr
2
Institut d’Astrophysique de Paris, CNRS et Sorbonne Université, UMR 7095, 98bis Bd Arago, 75014 Paris, France
3
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, 00-716 Warsaw, Poland
Received:
6
July
2020
Accepted:
1
October
2020
Context. It is now widely accepted that most ultraluminous X-ray sources (ULXs) are binary systems whose large (above 1039 erg s−1) apparent luminosities are explained by super-Eddington accretion onto a stellar-mass compact object. Many of the ULXs, especially those containing magnetized neutron stars, are highly variable; some exhibit transient behaviour. Large luminosities might imply large accretion discs that could be therefore prone to the thermal–viscous instability known to drive outbursts of dwarf novae and low-mass X-ray binary transient sources.
Aims. The aim of this paper is to extend and generalize the X-ray transient disc-instability model to the case of large (outer radius larger than 1012 cm) accretion discs and apply it to the description of systems with super-Eddington accretion rates at outburst and, in some cases, super-Eddington mass transfer rates.
Methods. We have used our disc-instability-model code to calculate the time evolution of the accretion disc and the outburst properties.
Results. We show that, provided that self-irradiation of the accretion disc is efficient even when the accretion rate exceeds the Eddington value, possibly due to scattering back of the X-ray flux emitted by the central parts of the disc on the outer portions of the disc, heating fronts can reach the disc’s outer edge generating high accretion rates. We also provide analytical approximations for the observable properties of the outbursts. We have successfully reproduced the observed properties of galactic transients with large discs, such as V404 Cyg, as well as some ULXs such as M51 XT-1. Our model can reproduce the peak luminosity and decay time of ESO 243-39 HLX-1 outbursts if the accretor is a neutron star.
Conclusions. Observational tests of our predicted relations between the outburst duration and decay time with peak luminosity would be most welcome.
Key words: accretion / accretion discs / X-rays: binaries / instabilities
© J.-M. Hameury and J.-P. Lasota 2020
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.