Phase variations of the FWHM, folded at a stellar rotation period of 2.23 days. The data sets are computed with the default (black), high-g_eff (yellow), and low-g_eff (purple) mask for three epochs: 2019a (top left), 2019b (top right), 2020a (bottom left), 2020b (bottom right). Although no evident rotational modulation is observed, we notice a long-term oscillation of the mean value in a similar way to the longitudinal field (absolute) values.