M. Del Santo
M. van der Klis
- Broad-band X-ray spectral evolution of GX 339−4 during a state transition
- Monthly Notices of the Royal Astronomical Society
- Volume | Issue number
- 392 | 3
- Pages (from-to)
- Document type
- Faculty of Science (FNWI)
- Anton Pannekoek Institute for Astronomy (API)
We report on X-ray and soft γ-ray observations of the black hole candidate GX 339−4 during its 2007 outburst, performed with the RXTE and INTEGRAL satellites. The hardness-intensity diagram of all RXTE/PCA data combined shows a q-shaped track similar to that observed in previous outbursts. The evolution in the diagram suggested that a transition from hard- to soft-intermediate state occurred, simultaneously with INTEGRAL observations performed in March. The transition is confirmed by the timing analysis presented in this work, which reveals that a weak type-A quasi-periodic oscillation (QPO) replaces a strong type-C QPO. At the same time, spectral analysis shows that the flux of the high-energy component shows a significant decrease in its flux. However, we observe a delay (roughly one day) between variations of the spectral parameters of the high-energy component and changes in the flux and timing properties. The changes in the high-energy component can be explained either in terms of the high-energy cut-off or in terms of variations in the reflection component. We compare our results with those from a similar transition during the 2004 outburst of GX 339−4.
- go to publisher's site
- DOI: 10.1111/j.1365-2966.2008.14111.x; eprintid: arXiv:0810.3556
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