Left: light curve for the EHB star 248955 from April 25th. A low-order polynomial was fit to remove differential extinction over the night, and outliers were removed. The black points represent the original ULTRACAM u′ data with a sampling time of 6 s while the magenta points have been binned to 100 s to reduce the noise and reveal the long-period luminosity variations more clearly. Right: Fourier spectrum of the combined light curve from 22–25 April in the 0–1 mHz range. The horizontal dashed line indicates 4 times the mean noise level, above which the excess power around 0.34 mHz is clearly visible.