Rotation periods as a function of effective temperature for a group of 38 987 low-mass MS stars in the Kepler field, compared with a smaller group of 66 Kepler low-mass main-sequence stars and with theoretical data from models. Data represented in blue and red are the same data shown in Figure 8. In this plot, we add a third regression model fitted to the observational data, for a set of 38987 stars from the catalog by Santos et al. (2021b).