Professor Tim Roberts t.p.roberts@durham.ac.uk
Professor
A variable ultraluminous X-ray source in a globular cluster in NGC 4649
Roberts, T.P.; Fabbiano, G.; Luo, B.; Kim, D.-W.; Strader, J.; Middleton, M.J.; Brodie, J.P.; Fragos, T.; Gallagher, J.S.; Kalogera, V.; King, A.R.; Zezas, A.
Authors
G. Fabbiano
B. Luo
D.-W. Kim
J. Strader
M.J. Middleton
J.P. Brodie
T. Fragos
J.S. Gallagher
V. Kalogera
A.R. King
A. Zezas
Abstract
We report the discovery of a new ultraluminous X-ray source associated with a globular cluster in the elliptical galaxy NGC 4649. The X-ray source was initially detected with a luminosity below 5 × 1038 erg s–1, but in subsequent observations 7 and 11 years later it had brightened substantially to 2-3 × 1039 erg s–1. Over the course of six separate observations it displayed significant spectral variability, in both continuum slope and absorption column. Short-term variability in the X-ray flux was also present in at least one observation. The properties of this object appear consistent with a stellar-mass black hole accreting at super-Eddington rates (i.e., in the ultraluminous accretion state), although a highly super-Eddington neutron star cannot be excluded. The coincidence of an increase in absorption column with a possible enhancement in short-term variability in at least one observation is suggestive of a clumpy, radiatively driven wind crossing our line of sight to the object.
Citation
Roberts, T., Fabbiano, G., Luo, B., Kim, D., Strader, J., Middleton, M., …Zezas, A. (2012). A variable ultraluminous X-ray source in a globular cluster in NGC 4649. Astrophysical Journal, 760(2), Article 135. https://doi.org/10.1088/0004-637x/760/2/135
Journal Article Type | Article |
---|---|
Publication Date | Dec 1, 2012 |
Deposit Date | Mar 26, 2013 |
Publicly Available Date | Feb 12, 2014 |
Journal | Astrophysical Journal |
Print ISSN | 0004-637X |
Electronic ISSN | 1538-4357 |
Publisher | American Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 760 |
Issue | 2 |
Article Number | 135 |
DOI | https://doi.org/10.1088/0004-637x/760/2/135 |
Keywords | Globular clusters, X-rays, Binaries, Galaxies. |
Files
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Copyright Statement
© 2012. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
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