Catching Up on State Transitions in Cygnus X-1
  In 2005 February we observed Cygnus X-1 over a period of 10 days quasi-continuously with the Rossi X-ray Timing Explorer and the Ryle telescope. We present the results of the spectral and timing analysis on a timescale of 90 min and show that the behavior of Cyg X-1 is similar to that found during our years long monitoring campaign. As a highlight we present evidence for a full transition from the hard to the soft state that happened during less than three hours. The observation provided a more complete picture of a state transition than before, especially concerning the evolution of the time lags, due to unique transition coverage and analysis with high time resolution. 
Moritz Boeck, Manfred Hanke, Joern Wilms, Victoria Grinberg, Katja   Pottschmidt, Sera Markoff, Michael A. Nowak, Stefan Pir...