Four examples of qualitatively different signal detections. Top left: no signal (HD 45067). Top right: 1σ signal (HD 39881). Bottom left: 2σ detection (HD 72905). Bottom right: 3σ detection (HD 37394). Each figure contains the original time series (top left), including a polynomial fit (full line) to eliminate a long-term trend, the time series corrected for a long-term trend (top right), the Scargle periodogram (bottom left) and a phase plot (bottom right).