Superoutbursts of the SU UMa-type dwarf nova CP Draconis

Analysis of observations of the SU UMa-type dwarf nova, CP Dra, between February 2001 and April 2009 has revealed 15 outbursts, at least eight of which were superoutbursts. The supercycle length is 230+/-56 d. We report photometry of the 2001 and 2009 superoutbursts which shows that they were remarkably similar to each other in terms of the profile of the outburst light curve and the evolution of the superhumps. The outburst amplitude was 5.5 magnitudes and the Psh during the plateau phase was measured at 0.08335(31) and 0.08343(21) d, respectively. In both cases, Psh decreased during the course of the outburst and there is some evidence that there was an abrupt change corresponding to the point in the plateau where a slow fade begins. The 2001 superoutburst was caught during the rise to maximum and during this period we found that the Psh was significantly longer than during the subsequent stages. Superhumps of 0.3 magnitude peak-to-peak amplitude were present at the height of each outburst and these gradually diminished during the outburst. We also report photometry from the 2002 superoutburst, although coverage was not so extensive, which revealed Psh = 0.08348(32) d consistent with the other two superoutbursts. Analysis of time resolved photometry from the 2009 outburst revealed evidence for an orbital period of 0.08084(86) d, giving a fractional superhump period excess epsilon = 0.032(3) d.