2007A&A...463.1053S

WXCet is a dwarf nova with rare outbursts of large amplitude. We compile the available data of WXCet, compare the results with other SUUMa stars, and discuss our findings in the context of current theories of superhumps and superoutbursts to progress with our understanding of SUUMa stars. We analyse all recorded outbursts of WX Cet, based on the AAVSO archive and other published sources, and present new CCD photometry during two recent superoutbursts, including the determination of the corresponding periodicities. We perform numerical disc instability model calculations and compare its predictions with the observations. WXCet is a SUUMa type dwarf nova with a superoutburst cycle of 880 days on average, and short eruptions every 200 days. It seems that the outburst cycle length increased by nearly a factor of 2 during the past 70 years. According to our numerical simulations, this can be explained in the context of the disc instability model by assuming enhanced mass transfer during outburst and a decreasing mean mass transfer rate during the last decades. Using the data available, we refine the orbital period of WXCet to 0.0582610±0.0000002 days and interpret the orbital hump found in quiescence as emission from the hot spot. During two recent superoutbursts in July 2001 and December 2004 we observed superhumps, with a rather large positive period derivative of {dot}(P)_s/P_s=1.6x10^–4, present only during the first 9 days of a superoutburst. Afterwards and during decline from the ``plateau'' phase, a constant superhump period of about 0.05922 days was observed. Late superhumps are present for at least 12 days after the decline from the ``plateau'', with a period of 0.05927 days. We find this phenomenology difficult to interpret in the context of the standard explanation for superhumps, i.e. the thermal tidal instability model. We interpret the long-term light curve of WXCet as the result of a significantly decreasing mean mass transfer rate. Highlighting the complexity of the observed superhump light curves, we emphasise the importance of WXCet for a proper understanding of the SUUMa star outburst physics and the evolution of ultra-short period cataclysmic variables.