Spectrum of BU CMi near the Mg ii 4481 line (4470–4490 Å segment, plotted with red solid curve) and the optimum multicomponent fit (black solid curve) for the first 20 spectra. Each panel shows the orbital phases of the inner subsystems and the epoch (HJD-2 400 000) typed in black on the left, and the model RVs of the binary subsystems on the right. Magenta is used for the predicted RVs, the orbital phase and spectrum of the A sub-system (P = 2.94 d), while blue is used for the same plot elements for the B sub-system (P = 3.26 d).