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X-Ray Outflows and Super-Eddington Accretion in the Ultraluminous X-Ray Source Holmberg IX X-1

Walton, D.J.; Miller, J.M.; Harrison, F.A.; Fabian, A.C.; Roberts, T.P.; Middleton, M.J.; Reis, R.C.

X-Ray Outflows and Super-Eddington Accretion in the Ultraluminous X-Ray Source Holmberg IX X-1 Thumbnail


D.J. Walton

J.M. Miller

F.A. Harrison

A.C. Fabian

M.J. Middleton

R.C. Reis


Studies of X-ray continuum emission and flux variability have not conclusively revealed the nature of ultraluminous X-ray sources (ULXs) at the high-luminosity end of the distribution (those with LX 1040 erg s−1). These are of particular interest because the luminosity requires either super-Eddington accretion onto a black hole of mass ∼10 M or more standard accretion onto an intermediate-mass black hole. Super-Eddington accretion models predict strong outflowing winds, making atomic absorption lines a key diagnostic of the nature of extreme ULXs. To search for such features, we have undertaken a long, 500 ks observing campaign on Holmberg IX X-1 with Suzaku. This is the most sensitive data set in the iron K bandpass for a bright, isolated ULX to date, yet we find no statistically significant atomic features in either emission or absorption; any undetected narrow features must have equivalent widths less than 15–20 eV at 99% confidence. These limits are far below the 150 eV lines expected if observed trends between mass inflow and outflow rates extend into the super-Eddington regime and in fact rule out the line strengths observed from disk winds in a variety of sub-Eddington black holes. We therefore cannot be viewing the central regions of Holmberg IX X-1 through any substantial column of material, ruling out models of spherical super-Eddington accretion. If Holmberg IX X-1 is a super-Eddington source, any associated outflow must have an anisotropic geometry. Finally, the lack of iron emission suggests that the stellar companion cannot be launching a strong wind and that Holmberg IX X-1 must primarily accrete via Roche-lobe overflow.


Walton, D., Miller, J., Harrison, F., Fabian, A., Roberts, T., Middleton, M., & Reis, R. (2013). X-Ray Outflows and Super-Eddington Accretion in the Ultraluminous X-Ray Source Holmberg IX X-1. Astrophysical Journal Letters, 773(1), Article L9.

Journal Article Type Article
Publication Date Aug 1, 2013
Deposit Date Sep 11, 2013
Publicly Available Date Jan 28, 2014
Journal Astrophysical Journal Letters
Print ISSN 2041-8205
Electronic ISSN 2041-8213
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 773
Issue 1
Article Number L9
Keywords Black hole, Physics, X-rays, Binaries, Holmberg IX X-1.


Published Journal Article (499 Kb)

Copyright Statement
© 2013. The American Astronomical Society. All rights reserved.

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