Curious Variables Experiment (CURVE). TT Bootis - superhump period change pattern confirmed

We report extensive multi-station photometry of TT Boo during its June 2004 superoutburst. The amplitude of the superoutburst was about 5.5 mag and its length over 22 days. The star showed a small re-brightening starting around the 9th day of the superoutburst. During entire bright state we observed clear superhumps with amplitudes from 0.07 to 0.26 mag and a mean period of Psh = 0.0779589(47) days (112.261 +/- 0.007 min). The period was not constant but decreased at the beginning and the end of superoutburst yet increased in the middle phase. We argue that the complicated shape of the O-C diagram is caused by real period changes rather than by phase shifts. Combining the data from two superoutbursts from 1989 and 2004 allowed us to trace the birth of the late superhumps and we conclude that it is a rather quick process lasting about one day.