SIMBAD references

Fundamental astrophysical parameters (distance, temperature, luminosity, mass, age) of a sample of 10 Herbig Ae/Be candidates and 3 non-emission line A and B stars in star forming regions were computed combining Hipparcos parallaxes with data from literature. All genuine Herbig stars in our sample are located between the birthline and the zero-age main sequence (ZAMS) in the Hertzsprung-Russell diagram (HRD), in accordance with what is expected for pre-main sequence stars. The region in the HRD close to the birthline is relatively devoid of stars when compared to the region closer to the ZAMS, in agreement with the expected evolutionary time scales. The Herbig Ae/Be stars not associated with star forming regions were found to be located close to the ZAMS. Additionally we discuss a possible evolutionary scenario for the circumstellar environment of Herbig stars.