Skip to main content

Research Repository

Advanced Search

X-ray spectral residuals in NGC 5408 X-1: diffuse emission from star formation, or the signature of a super-Eddington wind?

Sutton, A.D.; Roberts, T.P.; Middleton, M.J.

X-ray spectral residuals in NGC 5408 X-1: diffuse emission from star formation, or the signature of a super-Eddington wind? Thumbnail


Authors

A.D. Sutton

M.J. Middleton



Abstract

If ultraluminous X-ray sources (ULXs) are powered by accretion onto stellar remnant black holes, then many must be accreting at super-Eddington rates. It is predicted that such high accretion rates should give rise to massive, radiatively driven winds. However, observational evidence of a wind, in the form of absorption or emission features, has remained elusive. As such, the reported detection of X-ray spectral residuals in XMM-Newton spectra of NGC 5408 X-1, which could be related to absorption in a wind is potentially very exciting. However, it has previously been assumed by several authors that these features simply originate from background diffuse plasma emission related to star formation in the ULX's host galaxy. In this work we utilize the spatial resolving power of Chandra to test whether we can rule out this latter interpretation. We demonstrate that the majority of the luminosity in these spectral features is emitted from a highly localized region close to the ULX, and appears point-like even with Chandra. It is therefore highly likely that the spectral features are associated with the ULX itself, and little of the flux in this spectral component originates from spatially extended emission in the host galaxy. This may be consistent with the suggestion of absorption in an optically thin phase of a super-Eddington wind. Alternatively, we could be seeing emission from collisionally ionized material close to the black hole, but critically this would be difficult to reconcile with models where the source inclination largely determines the observed X-ray spectral and timing properties.

Citation

Sutton, A., Roberts, T., & Middleton, M. (2015). X-ray spectral residuals in NGC 5408 X-1: diffuse emission from star formation, or the signature of a super-Eddington wind?. Astrophysical Journal, 814(1), Article 73. https://doi.org/10.1088/0004-637x/814/1/73

Journal Article Type Article
Acceptance Date Oct 10, 2015
Publication Date Nov 20, 2015
Deposit Date Nov 30, 2015
Publicly Available Date Mar 28, 2024
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 814
Issue 1
Article Number 73
DOI https://doi.org/10.1088/0004-637x/814/1/73
Keywords Accretion, Accretion disks, Black hole physics, X-rays: binaries.
Related Public URLs http://arxiv.org/pdf/1510.03853v1.pdf

Files

Published Journal Article (924 Kb)
PDF

Copyright Statement
© 2015. The American Astronomical Society. All rights reserved.





You might also like



Downloadable Citations