Diagram showing T_eff – F_bias. The diamond symbols represent the stars from Wood et al. (2018) and the square symbol corresponds to the additional stars from the sample of Seli et al. (2022). The circles represent the F_bias of HD 223889 for the flare and the quiescent phase. Each data point is plotted with the corresponding error bars for the effective temperature (T_eff) and the FIP bias value (F_bias). The two gray lines represent the fit of the lower and upper branches from Seli et al. (2022), Eqs. (2) and (4), respectively. The color-coded data points indicate log L_X (X-ray luminosity), which is also taken as an activity indicator.