Show simple item record

dc.contributor.authorSoria, Roberto
dc.contributor.authorMusaeva, A.
dc.contributor.authorWu, K.
dc.contributor.authorZampieri, L.
dc.contributor.authorFederle, S.
dc.contributor.authorUrquhart, Ryan
dc.contributor.authorvan der Helm, E.
dc.contributor.authorFarrell, S.
dc.identifier.citationSoria, R. and Musaeva, A. and Wu, K. and Zampieri, L. and Federle, S. and Urquhart, R. and van der Helm, E. et al. 2017. Outbursts of the intermediate-mass black hole HLX-1: a wind-instability scenario. Monthly Notices of the Royal Astronomical Society. 469 (1): pp. 886-905.

We model the intermediate-mass black hole HLX-1, using the Hubble Space Telescope, XMM–Newton and Swift. We quantify the relative contributions of a bluer component, function of X-ray irradiation, and a redder component, constant and likely coming from an old stellar population. We estimate a black hole mass ≈(2+2−1)×104M⊙ , a spin parameter a/M ≈ 0.9 for moderately face-on view and a peak outburst luminosity ≈0.3 times the Eddington luminosity. We discuss the discrepancy between the characteristic sizes inferred from the short X-ray time-scale (R ∼ a few 1011 cm) and from the optical emitter ( Rcosθ−−−−√≈2.2×1013  cm). One possibility is that the optical emitter is a circumbinary disc; however, we disfavour this scenario because it would require a very small donor star. A more plausible scenario is that the disc is large but only the inner annuli are involved in the X-ray outburst. We propose that the recurrent outbursts are caused by an accretion-rate oscillation driven by wind instability in the inner disc. We argue that the system has a long-term-average accretion rate of a few per cent Eddington, just below the upper limit of the low/hard state; a wind-driven oscillation can trigger transitions to the high/soft state, with a recurrence period ∼1 yr (much longer than the binary period, which we estimate as ∼10 d). The oscillation that dominated the system in the last decade is now damped such that the accretion rate no longer reaches the level required to trigger a transition. Finally, we highlight similarities between disc winds in HLX-1 and in the Galactic black hole V404 Cyg.

dc.publisherOxford University Press
dc.titleOutbursts of the intermediate-mass black hole HLX-1: a wind-instability scenario
dc.typeJournal Article
dcterms.source.titleMonthly Notices of the Royal Astronomical Society

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. All rights reserved.

curtin.departmentCurtin Institute of Radio Astronomy (Physics)
curtin.accessStatusOpen access

Files in this item


There are no files associated with this item.

This item appears in the following Collection(s)

Show simple item record