Four representative diagrams involving T_eff. In the four panels our investigated stars are represented with filled circles colour-coded by spectral type. Top left: comparison of T_eff from this work and from the literature. Top right: individual (coloured points) and median (black circles) values of T_eff as a function of the spectral sequence shown in Table 6. The size of the black circles is proportional to the number of stars per spectral type. The green, red, and blue lines mark the mean values tabulated by Pecaut & Mamajek (2013), Rajpurohit et al. (2018a), and Passegger et al. (2019), respectively. Bottom left: L vs. T_eff. As a comparison we also plot pre-main sequence stars with BT-Settl model fitting from Pecaut & Mamajek (2013, green empty circles), M dwarfs in the MEarth sample with stellar parameters from Newton et al. (2015, blue empty circles, inferred from the pseudo-equivalent width of Mg I near-infrared lines), and high-confidence moving group members from Faherty et al. (2016, magenta empty circles) with parameters computed as in Filippazzo et al. (2015). Bottom right: J-band absolute magnitude vs. T_eff. As a comparison we also plot the samples of Dahn et al. (2002, blue open circles), Lépine et al. (2013, green open circles), and Gaidos & Mann (2014, magenta empty circles).