Top: nightly Strömgren Δ y magnitudes from the T10 APT for the 2004–2005 observing season. The vertical dotted lines mark the JDs of the eclipse monitoring nights. Middle: frequency spectrum of the Δ y observations showing the best-fit period of 4.26 days, which we take to be half the stellar rotation period. Bottom: Δ y observations phased with the 4.26 day period have an amplitude of only 0.005 mag. The horizontal dashed lines in the top and bottom panels represent the mean brightness of the Δ y data set.