X-ray Spectral Variability of Ultraluminous X-ray Source Holmberg IX X-1
Abstract
Ultraluminous X-ray sources (ULXs) are compact, off-nuclear bright sources with X-ray luminosity, L_{X} > 10(39) erg/s. X-ray variability studies are very useful in understanding the nature and physical structure of ULXs. We use XMM-Newton and Suzaku data to study the spectral variability in the ULX, Holmberg IX X-1. We do a full spectral fitting with a disk plus thermal Comptonization models. In addition all the data are well fitted with low temperature Comptonizing corona. Holmberg IX X-1 shows a spectral variability, characterized by the increasing Comptonization power law index as the source become brighter. The variation in the luminosity by factor of ∼ 5 produces a change of about 0.3 in the power law index. However, the disk luminosity, hydrogen column density (n_{H}), plasma electron temperature (kT_{e}) and inner disk temperature (kT_{in}) are showing a marginal trend with luminosity even though with large uncertainties. The positive correlation between the luminosity and Comptonization power law index suggests that the variability mechanism is related to the geometry of the source.
- Publication:
-
40th COSPAR Scientific Assembly
- Pub Date:
- 2014
- Bibcode:
- 2014cosp...40E1340J