Position of CEN 34 in the Hertzsprung-Russell diagram (HRD) with a well determined effective temperature (5250 ± 250 K) and loosely constrained luminosity (1600 L_⊙ ≲ L_∗ ≲ 8100 L_⊙). Left panel: the position of CEN 34 denoted by the full dot with error bar is compared with the model of massive star formation via disk accretion (Hosokawa et al. 2010). The luminosity of 1600 L_⊙ adopted here is the lower limit (denoted by the upward arrow) when the distance of CEN 34 is assumed to be 2 kpc. Right panel: the position of CEN 34 (the rectangle representing the uncertainties of T_eff and L_∗) is placed against the isochrones of post-main-sequence evolution (Marigo et al. 2008). The lower and upper isochrones (roughly the 100 Myr and 50 Myr ones, respectively) that enclose the position of CEN 34 are highlighted in red, and the corresponding masses are highlighted in blue.