SIMBAD references

Hipparcos trigonometric parallaxes have been used to derive a photometric absolute magnitude calibration of main-sequence late A-type stars in terms of Stroemgren photometric indices - accounting for temperature, evolution and metallicity effects - and projected equatorial rotational velocities. The derived calibrations are valid for main-sequence normal A3-A9 and metallic Am stars, showing residuals of 0.22 and 0.20 magnitudes, respectively. One of the fitting methods used (BCES) allows the derivation of the observational ZAMS in this spectral range, showing an excellent accordance with theoretical evolutionary models. The evolutionary state of the Am stars is also discussed.