The Tycho-2 spectral type catalog

The Tycho-2 Catalogue contains positions, proper motions, and B-T and V-T magnitudes for approximately 2.5 million stars. We have obtained spectral types for 351,864 of the Tycho-2 stars by cross- referencing Tycho-2 to several catalogs containing spectral types, using the VizieR astronomical database. The positional matching requirements were stringent (97.5% of the matches were within 1), and the validity of the positional matches is further supported by the distribution of magnitude differences for matched pairs, which is symmetric about the median value (dV)(med) = 0.043 and has a small standard deviation, sigma(dV) = 0.40 mag.