Baykal et al. (2002) followed for the first time the pulse period evolution from an initial spin-up phase (in the first 150 days of the 1999 outburst), to a saturation,and then to a spin-down phase (as the flux was decreasing). In 150 days the pulse period decreased by 0.9 sec. A correlation between pulse period derivative and flux exists (Baykal et al. (2002) ). See Baykal et al. (2007) for updates on the timing studies and Inam et al. (2004) for a discussion of the 22.7s QPO.