Swift-XRT 6-year monitoring of the ultraluminous X-ray source M33-X8
arXiv:1601.08071 · doi:10.1051/0004-6361/201425384
Abstract
The long term evolution of ULX with their spectral and luminosity variations in time give important clues on the nature of ULX and on the accretion process that powers them. We report here the results of a Swift-XRT 6-year monitoring campaign of the closest example of a persistent ULX, M33 X-8, that extends to 16 years the monitoring of this source in the soft X-rays. The luminosity of this source is a few 10^39 erg/s, marking the faint end of the ULX luminosity function. We analysed the set of 15 observations collected during the Swift monitoring. We searched for differences in the spectral parameters at different observing epochs, adopting several models commonly used to fit the X-ray spectra of ULX. The source exhibits flux variations of the order of 30%. No significant spectral variations are observed along the monitoring. The average 0.5-10 keV spectrum can be well described by a thermal model, either in the form of a slim disk, or as a combination of a Comptonized corona and a standard accretion disk.
6 pages, 4 figures, 2 tables. Paper published in A&A
References in corpus (9)
- An Ultraluminous X-ray Source Powered by An Accreting Neutron Star
- Super-critically accreting stellar-mass black holes as ultraluminous X-ray sources
- The Nature of SS433 and the Ultraluminous X-ray Sources
- Masses, Beaming and Eddington Ratios in Ultraluminous X-ray Sources
- A spectral-timing model for ULXs in the super-critical regime
- Identification of the X-Ray Thermal Dominant State in an Ultraluminous X-Ray Source in M82
- X-ray spectral state is not correlated with luminosity in Holmberg II X-1
- The slim-disk state of the ultraluminous X-ray source in M83
- The X-ray properties of the dwarf Magellanic-type galaxy NGC 55
Cited by in corpus (7)
- Crossing the Eddington limit: examining disk spectra at high accretion rates
- On the Nature of the X-ray Emission from the Ultraluminous X-ray Source, M33 X-8: New Constraints from NuSTAR and XMM-Newton
- Investigating the nature of the ultraluminous X-ray sources in the galaxy NGC 925
- Central X-ray point-sources found to be abundant in low-mass, late-type galaxies predicted to contain an intermediate-mass black hole
- NuSTAR observations of the ultraluminous X-ray source M33 X-8: a black hole in a very high state?
- Recurrent outbursts revealed in 3XMM J031820.8-663034
- Comprehensive X-ray and Multiwavelength Study of ULXs in NGC 1566