Spectral classification of B and A stars from data of S2/S68 experiment

The S2/S68 experiment on the satellite TD1 A has supplied, in the wavelength region of 1350 A to 2550 A, a very large number of spectra of early stars. A statistical study, as well as a general analysis of these spectra, has been carried out in order to establish criteria relative to the spectral region envisaged and independent of any previous study in the visible. On the basis of these criteria a system of classification has been outlined. In a first stage, the spectra of stars visually classed from B0 to A5 have been considered. From four sets of spectrophotometric criteria a two-dimensional ultraviolet classification has been derived. (Auth.)