Pseudo-equivalent width of Hα line after subtracting an inactive reference star spectrum (pEW′_Hα) as a function of the stellar mass for 331 M dwarfs in the CARMENES sample, colour-coded by the rotation period P_rot. Black points are stars with unknown P_rot. The four stars studied in this work are marked with star symbols and their names. pEW′_Hα and P_rot are adopted from Schöfer et al. (2019) and references therein, stellar masses were generally computed from luminosities and effective temperatures as in Schweitzer et al. (2019) and Cifuentes et al. (2020), but with the latest Gaia EDR3 parallax and photometry (Gaia Collaboration 2021). More details on these updated masses will be provided in a forthcoming publication.