Generalised Lomb Scargle (GLS) periodograms to determine the frequencies of planet candidates. Top panel is a periodogram of the original data with instrumental upgrade offset removed. Middle panels are periodograms of the residuals to a 194-day Keplerian fit (upper middle) and a two-planet fit (lower middle). The horizontal lines represent false-alarm probability levels of 10% (dashed) and 1% (dotted), as calculated from a bootstrap Monte Carlo method. Also included for comparison is the window function of the sampling (bottom panel).