Semi-empirical HR diagram for Wd1-5 (diamond) and the population of bright OB supergiants (circles) and hypergiants (Wd1-33 and 42; diamonds) within Wd1 (following Negueruela et al. 2010). The solid lines represent the Geneva isochrones (Meynet & Maeder 2000) without rotation for log t = 6.7 (5 Myr; top, blue) and log t = 6.8 (6.3 Myr; bottom, brown). The dash-dotted line is the log t = 6.7 isochrone for high initial rotational velocity. We note that no correction has been made for binary contamination in the sample, which might be expected to contribute to the scatter in absolute magnitudes. Errorbars for Wd1-5 are those quoted in the text, while representative errorbars for the remaining stars are presented in the lower right corner of the plot. These represent typical uncertainties associated with an incorrect assignment of spectral type by ±0.5 subtypes (in T_eff), and 0.5 mag in M_V to take into account the absolute magnitude and bolometric correction calibrations (as the difference in M_V is negligible between spectral types at Ia luminosity class).