Curious Variables Experiment (CURVE). CCD Photometry of QW Serpentis in Superoutburst and Quiescence

We report extensive photometry of the dwarf nova QW Ser throughout its 2003 February superoutburst till quiescence. During the superoutburst the star displayed clear superhumps with a mean period of Psh = 0.07703(4) days. In the quiescence we observed a double humped wave characterized by a period of P=0.07457(2) days. As both periods obey the Stolz-Schoembs relation with a period excess equal to 3.30+/-0.06% the latter period is interpreted as the orbital period of the binary system.Comment: accepted for publication in A&A, 5 pages, 7 figure

Curious Variables Experiment (CURVE). Variable properties of the dwarf nova SS UMi

We report on extensive photometry of the dwarf nova SS Ursae Minoris throughout nine months of 2004. In total, we recorded two superoutbursts and 11 normal outbursts of the star. SS UMi has been known to show frequent superoutbursts with a mean interval of 84.7 days. Our data suggest that the interval between successive superoutbursts lengthened to 197 days, indicating that SS UMi entered a period of untypical behavior manifested by a growth in the quiescent magnitude of the star and a series of frequent, low-amplitude, normal outbursts observed from July to September 2004. The mean superhump period derived for the April 2004 superoutburst of SS UMi is 0.070149(16) days (101.015 min). Combining this value with an earlier orbital period determination, we were able to derive the period excess, which is equal to 3.5 +/- 1.6%, and estimate the mass ratio of the binary system as equal to q=0.16 +/- 0.07. During the entire superoutburst, the period decreased at a rate of $\dot P/P_{\rm sh} = -6.3(1.4) \times 10^{-5}$. However, detailed analysis of the timings of superhump maxima seem to suggest a more complex period change, with a decrease in the period during the first and last stages of the superoutburst but an increase in the middle interval.Comment: 9 pages, 8 figures, in print in Astronomy & Astrophysic