Activity indicators. Left panel: Hα flux versus T_eff. Right panel: $R_{\mathrm{H}\alpha }^{\mathrm{\prime }}$ versus T_eff. The three subsamples are distinguished with different symbols, as indicated in the legend. Upper limits are indicated by downward arrows. The straight dashed line in each panel is the boundary between chromospheric emission (below) and accretion as derived by Frasca et al. (2015). The dotted line in the $R_{\mathrm{H}\alpha }^{\mathrm{\prime }}$ plot marks the saturation level log($R_{\mathrm{H}\alpha }^{\mathrm{\prime }}$) = −3.7 estimated by Fang et al. (2018).