Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood

The following parameters are determined for 63 Galactic supergiants in the solar neighbourhood: effective temperature T(eff); surface gravity log g; iron abundance log epsilon(Fe); microturbulent parameter V(t); mass M/M(circle dot); age t and distance d. A significant improvement in the accuracy of the determination of log g, and all parameters dependent on it, is obtained through application of van Leeuwen rereduction of the Hipparcos parallaxes. The typical error in the log g values is now +/- 0.06 dex for supergiants with distances d < 300 pc and +/- 0.12 dex for supergiants with d between 300 and 700 pc; the mean error in T(eff) for these stars is +/- 120 K. For supergiants with d > 700 pc, parallaxes are uncertain or unmeasurable, so typical errors in their log g values are 0.2-0.3 dex. A new T(eff) scale for A5-G5 stars of luminosity classes Ib-II is presented. Spectral subtypes and luminosity classes of several stars are corrected. Combining the T(eff) and log g with evolutionary tracks, stellar masses and ages are determined; a majority of the sample has masses between 4 and 15M(circle dot) and, hence, their progenitors were early to middle B-type main-sequence stars. Using Fe II lines, which are insensitive to departures from local thermodynamic equilibrium, the microturbulent parameter V(t) and the iron abundance log epsilon (Fe) are determined from high-resolution spectra. The parameter V(t) is correlated with gravity: V(t) increases with decreasing log g. The mean iron abundance for the 48 supergiants with distances d < 700 pc is log epsilon(Fe)= 7.48 +/- 0.09, a value close to the solar value of 7.45 +/- 0.05, and thus the local supergiants and the Sun have the same metallicity.