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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 .

Broad‐band X‐ray spectral evolution of GX 339−4 during a state transition ★