High-Speed Photometry of AM CVn Stars.

We present high-speed photometry of three AM CVn stars discovered in the last few years (ES Cet, ‘2003aw’ and SDSS J1240). ES Cet has a very stable photometric modulation with a single period of 620.2117 (± 0.0002) s (Espaillat et al. 2005) which is identical to its spectroscopic period. The 2-sigma upper limit on the period derivative (P) of ES Cet is < 1.5 × 10-11, based on a 3-year observational baseline. Since the discovery of ‘2003aw’ in a supernova search, this AM CVn star has been observed during two outbursts and has a superhump modulation of Psh = 2041.5 ± 0.3 s. At quiescence, 2003aw is fairly faint (V ∼ 20.4 mag) and no orbital period has yet been derived for this system. Two of the AM CVn stars (V803 Cen and CR Boo) show rapid oscillations similar to the (longer-period) dwarf nova oscillations and quasi-periodic oscillations seen in hydrogen-rich high-M CVs (Warner 2004). © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]