Am Cvn Stars in the Uct Ccd Cv Survey

High speed photometry of the helium-transferring binary ES Cet – taken over a two-year period (2001 October – 2003 October) – shows a very stable photometric period of 620.211437 ± 0.000038 s, with a tentative indication of curvature in the O–C diagram suggesting a change in period at a rate of Ṗ ∼ 1.6×10 . Phase-resolved spectroscopy of ES Cet obtained with the Hobby-Eberly Telescope shows a clear modulation on the photometric period, the assumed orbital period. We have followed a newly identified AM CVn star (‘2003aw’) photometricaly through its 2003 February/March outburst during which it varied in brightness over a range of V = 16.5 – 20.3; we find a superhump period of 2041.5 ± 0.3 s. Questions are raised about the reality of the detected spin-up in RXJ0806 (Hakala et al. 2003; Strohmayer 2003).