Inaccuracies in the spectral classification of stars from the Tycho-2 Spectral Type Catalogue

We compare the spectroscopic and trigonometric parallaxes of common stars from the Tycho-2 Spectral Type and Hipparcos Catalogues. This comparison has revealed that the distance estimations for the overwhelming majority of stars by both methods yield very similar results. However, there is a small fraction of stars for which the distance estimates differ significantly. It is these stars that are the subject of our study. We have been able to find the causes of these differences.