Comments on the significance of the positions of population I Wolf-Rayet stars in the HR diagram

Ths size of typical errors in log L/L(Sun) and log Tsub(eff) is investigated for WR stars, and it is found that typically Δ log L/L(Sun) = +- (0.25 +- 0.03), and Δ log Tsub(eff) = +- (0.05 +- 0.02). The major sources of error are the uncertainties in the distance modulus of the star and the integrated continuous flux from about 1400 A to 1 μm or so. The same is true for O and early B stars. With uncertainties of these sizes in log L/L(Sun) and log Tsub(eff), it is unreliable to estimate the mass of an early-type star from its observed position in the HR diagram. The WN7/8 stars lie with the O9/B0 Ia stars, the other WR stars with the B0/B1 III stars. (Auth.)