Comparison between the K5 FWHM_DRS and the literature v_eq sin i_★ values. Upper panel: correlation between the K5 FWHM_DRS (x-axis) and the literature v_eq sin i_★values (y-axis), with the Spearman’s correlation coefficient r and p-value shown in the plot. The black line shows the linear fit of the data, the red dashed line shows the relation obtained from our selected calibrators (Eq. (7)), and the blue dotted line shows the linear fit after removing the stars with log ɡ < 3.5. Lower panels: residuals of the linear fitting, the relation from selected calibrators, and the linear fitting after removing the stars with log ɡ < 3.5.