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Evolution of the spectral curvature in the ultraluminous X-ray source Holmberg II X-1.
- Source :
-
Monthly Notices of the Royal Astronomical Society . May2012, Vol. 422 Issue 2, p990-996. 7p. 2 Charts, 3 Graphs. - Publication Year :
- 2012
-
Abstract
- ABSTRACT Ultraluminous X-ray sources (ULXs) are interesting systems as they can host intermediate-mass black holes. Alternatively, ULXs can represent stellar mass black holes accreting at super-Eddington rates. Recently, spectral curvature or breaks at energies above a few keV have been detected in high-quality ULX spectra. These spectral features have been taken as evidence against the intermediate-mass black hole case. In this paper, we report on a new XMM-Newton observation of the ULX Holmberg II X-1 that also shows a clear spectral break at approximately 4 keV. This observation was performed during a low-luminosity state of the system and by comparing these new data to a high-luminosity state XMM-Newton observation, we can conclude that the spectral break energy increases with luminosity. This behaviour is different from a ULX in the Holmberg IX galaxy, where an opposite trend between the luminosity and the spectral break energy has been claimed. We discuss mechanisms that could explain this complex behaviour. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 422
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 74574380
- Full Text :
- https://doi.org/10.1111/j.1365-2966.2012.20671.x