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

Walton, D. J. and Miller, J. M. and Harrison, F. A. and Fabian, A. C. and Roberts, T. P. and Middleton, M. J. and Reis, R. C. (2013) X-Ray Outflows and Super-Eddington Accretion in the Ultraluminous X-Ray Source Holmberg IX X-1. Astrophysical Journal Letters, 773 (1). Art. No. L9. ISSN 2041-8205. doi:10.1088/2041-8205/773/1/L9.

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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 L_X ≥ 10^(40) 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper DOIArticle
Walton, D. J.0000-0001-5819-3552
Harrison, F. A.0000-0003-2992-8024
Fabian, A. C.0000-0002-9378-4072
Roberts, T. P.0000-0001-8252-6337
Middleton, M. J.0000-0002-8183-2970
Additional Information:© 2013 The American Astronomical Society. Received 2013 April 27; accepted 2013 June 8; published 2013 July 26. The authors thank the reviewer for helpful comments. This research has made use of data obtained from the Suzaku observatory, a collaborative mission between the space agencies of Japan (JAXA) and the USA (NASA).
Group:Space Radiation Laboratory
Subject Keywords:black hole physics; X-rays: binaries; X-rays: individual (Holmberg IX X-1)
Issue or Number:1
Record Number:CaltechAUTHORS:20130909-090748501
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Official Citation:X-Ray Outflows and Super-Eddington Accretion in the Ultraluminous X-Ray Source Holmberg IX X-1 D. J. Walton et al. 2013 ApJ 773 L9
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41161
Deposited By: Tony Diaz
Deposited On:17 Sep 2013 23:30
Last Modified:10 Nov 2021 04:26

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