HR diagram showing the IMTT stars sample (blue) and the HAeBe sample from Vioque et al. (2018) (red) that lies within the same mass range as the IMTT stars. The pre-main-sequence evolutionary tracks (gray-solid) are from Siess et al. (2000). The isochrones shown are for 1 Myr (dotted), 2 Myr (dash-dotted), 3 Myr (red-solid), and 7 Myr (black-solid). The ZAMS (thick-dashed) is defined by the location when the nuclear luminosity provides 99% of the total stellar luminosity.