Journal article
X-ray spectral state is not correlated with luminosity in Holmberg II X-1
Astrophysical journal. Letters, Vol.724(2), pp.L148-L152
11/09/2010
DOI: 10.1088/2041-8205/724/2/L148
Abstract
Astrophysical Journal Letters724:L148-L152, 2010 The ultraluminous X-ray source (ULX) Holmberg II X-1 has been observed over 4
months in 2009/2010 by the Swift observatory. The source luminosity varied by a
factor of up to 14, reaching a maximum 0.3-10 keV luminosity of ~3.0E40 erg/s.
The spectral properties do not vary much over these 4 months, with only a
slight monotonic increase of the hardness ratio with the count rate. This means
that the erratic flaring activity of the source is not associated with spectral
changes, as seen in other ULXs. Conversely, comparison with data obtained by
Swift in 2006 shows a completely different picture: while at a luminosity also
seen in the 2009/2010 data, the source appears with a hard spectrum. Thus, it
appears that, as in Galactic black hole binaries, spectral states in this ULX
are not determined only by the X-ray luminosity.
Details
- Title: Subtitle
- X-ray spectral state is not correlated with luminosity in Holmberg II X-1
- Creators
- Fabien Grisé - University of IowaPhilip Kaaret - University of IowaHua Feng - Tsinghua UniversityJari KajavaSean Farrell - University of Leicester
- Resource Type
- Journal article
- Publication Details
- Astrophysical journal. Letters, Vol.724(2), pp.L148-L152
- DOI
- 10.1088/2041-8205/724/2/L148
- ISSN
- 2041-8205
- eISSN
- 2041-8213
- Publisher
- The American Astronomical Society
- Language
- English
- Date published
- 11/09/2010
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199663102771
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