MEarth photometry of CD Cet. Panel a: light curve used by Díez Alonso et al. (2019, black circles), Newton et al. (2016, adding blue squares), and this work (adding red triangles). Bottom panels: (b) GLS periodograms of data used by Díez Alonso et al. (2019), (c) data used byNewton et al. (2016), (d) 2017/18 season data, (e) all public RG715 MEarth data, and (f) of their residuals after subtracting the 170 d period. Ticks in panels d and e mark a 170 d period (solid black) and its one-year aliases (dashed black). The vertical red dashed line marks the 134 d period found in RV data and some spectral activity indicators, and the vertical red dotted line marks the 68 d period found in VIS channel RV data.