HR diagram compiling the positions of IMTTS from this study (red and black symbols), and of IMTTS and LMTTS (blue symbols), and HAeBes (faded symbols) from other studies. Black and gray symbols are stars in which no magnetic field has been detected. Red and blue symbols are stars for which a magnetic field has been detected: stars represent complex magnetic topologies, circles represent simple magnetic topologies, and squares represent undefined magnetic topologies. The sizes of the red and dark blue symbols are proportional to the maximum absolute value of the longitudinal magnetic field measurements for each star. A light blue symbol means no such measurement is available. The youngest magnetic HAeBe star (HD 190073) is indicated on the top-left corner as an isolated red circle. The shaded areas have the following meaning; orange: fully convective; green: radiative core + convective envelope; blue: fully radiative; and pink: convective core + radiative envelope. The evolutionary tracks (solid black line, ranging from 1.0–4.0 M_⊙), isochrones (solid white line) and ZAMS (lower dashed line) are from the CESAM code, while the birthline (upper dashed line) is from Behrend & Maeder (2001). The numbers above each evolutionary track are the stellar mass in solar units. The numbers beside each isochron is the stellar age. The thin orange line is the location where R_conv.env./R_⋆ = 40%.