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A bright ultraluminous X-ray source in NGC 5907

Sutton, A.D.; Roberts, T.P.; Gladstone, J.C.; Farrell, S.A.; Reilly, E.; Goad, M.R.; Gehrels, N.

A bright ultraluminous X-ray source in NGC 5907 Thumbnail


A.D. Sutton

J.C. Gladstone

S.A. Farrell

E. Reilly

M.R. Goad

N. Gehrels


We present a multimission X-ray analysis of a bright (peak observed 0.3–10 keV luminosity of ∼6 × 1040 erg s−1), but relatively highly absorbed ultraluminous X-ray source (ULX) in the edge-on spiral galaxy NGC 5907. The ULX is spectrally hard in X-rays (Γ ∼ 1.2–1.7, when fitted with an absorbed power law), and has a previously reported hard spectral break consistent with it being in the ultraluminous accretion state. It is also relatively highly absorbed for a ULX, with a column of ∼0.4–0.9 × 1022 atom cm−2 in addition to the line-of-sight column in our Galaxy. Although its X-ray spectra are well represented by accretion disc models, its variability characteristics argue against this interpretation. The ULX spectra instead appear dominated by a cool, optically thick Comptonizing corona. We discuss how the measured 9 per cent rms variability and a hardening of the spectrum as its flux diminishes might be reconciled with the effects of a very massive, radiatively driven wind and subtle changes in the corona, respectively. We speculate that the cool disc-like spectral component thought to be produced by the wind in other ULXs may be missing from the observed spectrum due to a combination of a low temperature (∼0.1 keV), and the high column to the ULX. We find no evidence, other than its extreme X-ray luminosity, for the presence of an intermediate mass black hole (MsBHs, ∼ 102−104 M⊙) in this object. Rather, the observations can be consistently explained by a massive (≳ 20 M⊙) stellar remnant black hole in a super-Eddington accretion state.


Sutton, A., Roberts, T., Gladstone, J., Farrell, S., Reilly, E., Goad, M., & Gehrels, N. (2013). A bright ultraluminous X-ray source in NGC 5907. Monthly Notices of the Royal Astronomical Society, 434(2), 1702-1712.

Journal Article Type Article
Publication Date Sep 11, 2013
Deposit Date Sep 11, 2013
Publicly Available Date Jan 27, 2014
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 434
Issue 2
Pages 1702-1712
Keywords Accretion discs, Black hole physics, X rays, Binaries, Galaxies.


Published Journal Article (456 Kb)

Copyright Statement
This article has been published in the Monthly Notices of the Royal Astronomical Society. © 2013 The Authors Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.

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