HR diagram of the Tycho λ Boo stars with Gaia parallaxes (Gaia Collaboration et al. 2016a, 2016b). The temperatures are from Table 1, and the evolutionary tracks (Z = 0.02) are from Bressan et al. (2012). Note that all of the λ Boo stars in this sample lie between the ZAMS and the TAMS. Stars showing infrared excesses attributable to a debris disk (see Table 3 and Section 5.2) are indicated with a red “halo” around the data point.